Cisco Industrial Ethernet 4000, 4010 and 5000 Switch Software. Configuration Guide (2022)

Configuring Interfaces

Configuring Ethernet Interfaces

Command

Purpose

duplex {auto | full | half}

Enter the duplex parameter for the interface.

Note: The default duplex mode is full when an FE SFP module is

inserted.

Enable half-duplex mode (for interfaces operating only at 10 or

100 Mbps). You cannot configure half-duplex mode for interfaces

operating at 1000 Mbps.

You can configure the duplex setting when the speed is set to auto.

This command is not available on SFP module ports with these

exceptions:

If a Cisco 1000BASE-T SFP module is inserted, you can

configure duplex to auto or to full.

If a Cisco 100BASE-FX SFP module is inserted, you can

configure duplex to full or to half. Although the auto keyword is

available, it puts the interface in half-duplex mode (the default).

end

Return to privileged EXEC mode.

show interfaces interface-id

Display the interface speed and duplex mode configuration.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Use the no speed and no duplex interface configuration commands to return the interface to the default speed and

duplex settings (autonegotiate). To return all interface settings to the defaults, use the default interface interface-id

interface configuration command.

This example shows how to set the interface speed to 10 Mbps and the duplex mode to half on a 10/100 Mbps port:

Switch# configure terminal

Switch(config)# interface fasttethernet0/3

Switch(config-if)# no shutdown

Switch(config-if)# speed 10

Switch(config-if)# duplex half

This example shows how to set the interface speed to 100 Mbps on a 10/100/1000 Mbps port:

Switch# configure terminal

Switch(config)# interface GigabitEthernet1/18

Switch(config-if)# speed 100

Configuring a Power Management Mode on a PoE Port

For most situations, the default configuration (auto mode) works well, providing plug-and-play operation. No further

configuration is required. However, use the following procedure to give a PoE port higher priority, to make it data only, or

to specify a maximum wattage to disallow high-power powered devices on a port.

Note: When you make PoE configuration changes, the port being configured drops power. Depending on the new

configuration, the state of the other PoE ports, and the state of the power budget, the port might not be powered up

again. For example, port 1 is in the auto and on state, and you configure it for static mode. The switch removes power

from port 1, detects the powered device, and repowers the port. If port 1 is in the auto and on state and you configure

it with a maximum wattage of 10 W, the switch removes power from the port and then redetects the powered device.

The switch repowers the port only if the powered device is a Class 1, Class 2, or a Cisco-only powered device.

Beginning in privileged EXEC mode, follow these steps to configure a power management mode on a PoE-capable port:

Configuring Interfaces

Configuring Ethernet Interfaces

Command

Purpose

configure terminal

Enter global configuration mode.

interface interface-id

Specify the physical port to be configured, and enter interface

configuration mode.

power inline {auto [max max-wattage] |

Configure the PoE mode on the port. The keywords have these meanings:

never | static [max max-wattage]}

auto—Enable powered-device detection. If enough power is

available, automatically allocate power to the PoE port after device

detection. This is the default setting.

(Optional) max max-wattage—Limit the power allowed on the port. The

range is 4000 to 30000 mW. The default is 30000 mW.

never—Disable device detection, and disable power to the port.

Note: If a port has a Cisco powered device connected to it, do not use

the power inline never command to configure the port. A false link-up

can occur, placing the port into an error-disabled state.

static—Enable powered-device detection. Pre-allocate (reserve)

power for a port before the switch discovers the powered device.

The switch reserves power for this port even when no device is

connected and guarantees that power will be provided upon device

detection.

The switch allocates power to a port configured in static mode before it

allocates power to a port configured in auto mode.

end

Return to privileged EXEC mode.

show power inline [interface-id]

Display PoE status for the switch or for the specified interface.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Budgeting Power for Devices Connected to a PoE Port

When Cisco powered devices are connected to PoE ports, the switch uses Cisco Discovery Protocol (CDP) to determine

the actual power consumption of the devices, and the switch adjusts the power budget accordingly. The CDP protocol

works with Cisco powered devices and does not apply to IEEE third-party powered devices. For these devices, when the

switch grants a power request, the switch adjusts the power budget according to the powered-device IEEE classification.

If the powered device is a Class 0 (class status unknown) or a Class 3, the switch budgets 30,000 milliwatts for the

device, regardless of the actual amount of power needed. If the powered device reports a higher class than its actual

consumption or does not support power classification (defaults to Class 0), the switch can power fewer devices because

it uses the IEEE class information to track the global power budget.

By using the power inline consumption wattage configuration command, you can override the default power

requirement specified by the IEEE classification. The difference between what is mandated by the IEEE classification and

what is actually needed by the device is reclaimed into the global power budget for use by additional devices. You can

then extend the switch power budget and use it more effectively.

Caution: You should carefully plan your switch power budget and make certain not to oversubscribe the power

supply.

Note: When you manually configure the power budget, you must also consider the power loss over the cable between

the switch and the powered device.

Configuring Interfaces

Configuring Ethernet Interfaces

When you enter the power inline consumption default wattage or the no power inline consumption default global

configuration command, or the power inline consumption wattage or the no power inline consumption interface

configuration command this caution message appears:

%CAUTION: Interface interface-id: Misconfiguring the 'power inline consumption/allocation' command may

cause damage to the switch and void your warranty. Take precaution not to oversubscribe the power

supply.

It is recommended to enable power policing if the switch supports it.

Refer to documentation.

If the power supply is over-subscribed to by up to 20 percent, the switch continues to operate but its reliability is reduced.

If the power supply is subscribed to by more than 20 percent, the short-circuit protection circuitry triggers and shuts the

switch down.

For more information about the IEEE power classifications, see Power over Ethernet Ports, page 21.

Beginning in privileged EXEC mode, follow these steps to configure the amount of power budgeted to a powered device

connected to each PoE port on a switch:

Command

Purpose

configure terminal

Enter global configuration mode.

no cdp run

(Optional) Disable CDP.

power inline consumption default

Configure the power consumption of powered devices connected to

wattage

each the PoE port on the switch. The range for each device is 4000 to

15400 mW. The default is 15400 mW.

end

Return to privileged EXEC mode.

show power inline consumption

Display the power consumption status.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To return to the default setting, use the no power inline consumption default global configuration command.

Beginning in privileged EXEC mode, follow these steps to configure amount of power budgeted to a powered device

connected to a specific PoE port:

Command

Purpose

configure terminal

Enter global configuration mode.

no cdp run

(Optional) Disable CDP.

interface interface-id

Specify the physical port to be configured, and enter interface

configuration mode.

power inline consumption wattage

Configure the power consumption of a powered device connected to a

PoE port on the switch. The range for each device is 4000 to 15400 mW.

The default is 15400 mW.

Note: When you use this command, we recommend you also enable

power policing.

end

Return to privileged EXEC mode.

show power inline consumption

Display the power consumption status.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To return to the default setting, use the no power inline consumption interface configuration command.

Configuring Interfaces

Configuring Ethernet Interfaces

Beginning in privileged EXEC mode, follow these steps to configure amount of power budgeted to a powered device

connected to a specific PoE port:

Command

Purpose

configure terminal

Enter global configuration mode.

no cdp run

(Optional) Disable CDP.

interface interface-id

Specify the physical port to be configured, and enter interface

configuration mode.

power inline consumption wattage

Configure the power consumption of a powered device connected to a

PoE port on the switch. The range for each device is 4000 to 15400 mW.

The default is 15400 mW.

end

Return to privileged EXEC mode.

show power inline consumption

Display the power consumption status.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To return to the default setting, use the no power inline consumption interface configuration command.

Configuring IEEE 802.3x Flow Control

802.3x flow control enables connected Ethernet ports to control traffic rates during congestion by allowing congested

nodes to pause link operation at the other end. If one port experiences congestion and cannot receive any more traffic,

it notifies the other port by sending a pause frame to stop sending until the condition clears. Upon receipt of a pause

frame, the sending device stops sending any data packets, which prevents any loss of data packets during the

congestion period.

Note: Ports can receive, but not send, pause frames.

You use the flowcontrol interface configuration command to set the interface’s ability to receive pause frames to on,

off, or desired. The default state is off.

When set to desired, an interface can operate with an attached device that is required to send flow-control packets or

with an attached device that is not required to but can send flow-control packets.

These rules apply to 802.3x flow control settings on the device:

receive on (or desired): The port cannot send pause frames but can operate with an attached device that is required

to or can send pause frames; the port can receive pause frames.

receive off: 802.3x flow control does not operate in either direction. In case of congestion, no indication is given to

the link partner, and no pause frames are sent or received by either device.

Beginning in privileged EXEC mode, follow these steps to configure 802.3x flow control on an interface:

Command

Purpose

configure terminal

Enter global configuration mode

interface interface-id

Specify the physical interface to be configured, and enter

interface configuration mode.

no shutdown

Enable the port, if necessary. By default, UNIs and ENIs are

disabled, and NNIs are enabled.

flowcontrol {receive} {on | off | desired}

Configure the 802.3x flow control mode for the port.

Configuring Interfaces

Configuring Ethernet Interfaces

Command

Purpose

end

Return to privileged EXEC mode.

show interfaces interface-id

Verify the interface 802.3x flow control settings.

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To disable 802.3x flow control, use the flowcontrol receive off interface configuration command.

This example shows how to enable 802.3x flow control on a port:

Switch# configure terminal

Switch(config)# interface GigabitEthernet1/17

Switch(config-if)# flowcontrol receive on

Switch(config-if)# end

Configuring Auto-MDIX on an Interface

When automatic medium-dependent interface crossover (auto-MDIX) is enabled on an interface, the interface

automatically detects the required cable connection type (straight through or crossover) and configures the connection

appropriately. When connecting switches without the auto-MDIX feature, you must use straight-through cables to

connect to devices such as servers, workstations, or routers and crossover cables to connect to other switches or

repeaters. With auto-MDIX enabled, you can use either type of cable to connect to other devices, and the interface

automatically corrects for any incorrect cabling. For more information about cabling requirements, see the hardware

installation guide.

Auto-MDIX is enabled by default. When you enable auto-MDIX, you must also set the speed and duplex on the interface

to auto so that the feature operates correctly. Auto-MDIX is supported on all 10/100 and 10/100/1000 Mbps interfaces

and on Cisco 10/100/1000 BASE-T/TX SFP module interfaces. It is not supported on 1000 BASE-SX or -LX SFP module

interfaces.

Table 4 shows the link states that result from auto-MDIX settings and correct and incorrect cabling.

Local Side Auto-MDIX

Remote Side Auto-MDIX

With Correct Cabling

With Incorrect Cabling

Link up

Off

Link up

Off

Link up

Off

Link up

Link down

Beginning in privileged EXEC mode, follow these steps to configure auto-MDIX on an interface:

Command

Purpose

configure terminal

Enter global configuration mode

interface interface-id

Specify the physical interface to be configured, and enter interface

configuration mode.

no shutdown

Enable the port, if necessary. By default, UNIs and ENIs are disabled, and

NNIs are enabled.

speed auto

Configure the interface to autonegotiate speed with the connected device.

duplex auto

Configure the interface to autonegotiate duplex mode with the connected

device.

mdix auto

Enable auto-MDIX on the interface.

Configuring Interfaces

Configuring Ethernet Interfaces

Command

Purpose

end

Return to privileged EXEC mode.

show controllers ethernet-controller

Verify the operational state of the auto-MDIX feature on the interface.

interface-id phy

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To disable auto-MDIX, use the no mdix auto interface configuration command.

This example shows how to enable auto-MDIX on a port:

Switch# configure terminal

Switch(config)# interface GigabitEthernet1/17

Switch(config-if)# no shutdown

Switch(config-if)# speed auto

Switch(config-if)# duplex auto

Switch(config-if)# mdix auto

Switch(config-if)# end

Adding a Description for an Interface

You can add a description about an interface to help you remember its function. The description appears in the output

of these privileged EXEC commands: show configuration, show running-config, and show interfaces.

Beginning in privileged EXEC mode, follow these steps to add a description for an interface:

Command

Purpose

configure terminal

Enter global configuration mode.

interface interface-id

Specify the interface for which you are adding a description, and enter

interface configuration mode.

description string

Add a description (up to 240 characters) for an interface.

end

Return to privileged EXEC mode.

show interfaces interface-id

Verify your entry.

description

show running-config

copy running-config startup-config

(Optional) Save your entries in the configuration file.

Use the no description interface configuration command to delete the description.

This example shows how to add a description on a port and how to verify the description:

Switch# config terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface GigabitEthernet1/18

Switch(config-if)# description Connects to Marketing

Switch(config-if)# end

Switch# show interfaces GigabitEthernet1/18 description

Interface Status

Protocol Description

Gi 0/2

admin down

down

Connects to Marketing

Configuring Interfaces

Configuring Layer 3 Interfaces

The switch must be running the IP services image to support Layer 3 interfaces:

SVIs: You should configure SVIs for any VLANs for which you want to route traffic. SVIs are created when you enter

a VLAN ID following the interface vlan global configuration command. To delete an SVI, use the no interface vlan

global configuration command. You cannot delete interface VLAN 1.

When you create an SVI, it does not become active until it is associated with a physical port.

Routed ports: Routed ports are physical ports configured to be in Layer 3 mode by using the no switchport interface

configuration command.

Layer 3 EtherChannel ports: EtherChannel interfaces made up of routed ports.

A Layer 3 switch can have an IP address assigned to each routed port and SVI.

There is no defined limit to the number of SVIs and routed ports that can be configured in a switch. However, the

interrelationship between the number of SVIs and routed ports and the number of other features being configured might

have an impact on CPU usage because of hardware limitations. If the switch is using maximum hardware resources,

attempts to create a routed port or SVI have these results:

If you try to create a new routed port, the switch generates a message that there are not enough resources to convert

the interface to a routed port, and the interface remains as a switch port.

If you try to create an extended-range VLAN, an error message is generated, and the extended-range VLAN is

rejected.

If the switch attempts to boot up with a configuration that has more VLANs and routed ports than hardware can

support, the VLANs are created, but the routed ports are shut down, and the switch sends a message that this was

due to insufficient hardware resources.

All Layer 3 interfaces require an IP address to route traffic. This procedure shows how to configure an interface as a Layer

3 interface and how to assign an IP address to an interface.

Note: If the physical port is in Layer 2 mode (the default), you must enter the no switchport interface configuration

command to put the interface into Layer 3 mode. Entering a no switchport command disables and then re-enables the

interface, which might generate messages on the device to which the interface is connected. Furthermore, when you put

an interface that is in Layer 2 mode into Layer 3 mode, the previous configuration information related to the affected

interface might be lost, and the interface is returned to its default configuration

Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 interface:

Command

Purpose

configure terminal

Enter global configuration mode.

interface {{fastethernet | gigabitethernet} interface-id} |

Specify the interface to be configured as a Layer 3

{vlan vlan-id} | {port-channel port-channel-number}

interface, and enter interface configuration mode.

no shutdown

Enable the port, if necessary. By default, UNIs and ENIs

are disabled, and NNIs are enabled.

no switchport

For physical ports only, enter Layer 3 mode.

ip address ip_address subnet_mask

Configure the IP address and IP subnet.

no shutdown

Enable the interface.

Configuring Interfaces

Configuring the System MTU

Command

Purpose

end

Return to privileged EXEC mode.

show interfaces [interface-id]

Verify the configuration.

show ip interface [interface-id]

show running-config interface [interface-id]

copy running-config startup-config

(Optional) Save your entries in the configuration file.

To remove an IP address from an interface, use the no ip address interface configuration command.

This example shows how to configure a port as a routed port and to assign it an IP address:

Switch# configure terminal

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)# interface GigabitEthernet1/18

Switch(config-if)# no switchport

Switch(config-if)# ip address 192.20.135.21 255.255.255.0

Configuring the System MTU

The default maximum transmission unit (MTU) size for frames received and sent on all interfaces on the switch is 1500

bytes. You can increase the MTU size for all interfaces operating at 10 or 100 Mbps by using the system mtu global

configuration command. You can increase the MTU size to support jumbo frames on all Gigabit Ethernet interfaces by

using the system mtu jumbo global configuration command. You can change the MTU size for routed ports by using the

system mtu routing global configuration command.

Note: You cannot configure a routing MTU size that exceeds the system MTU size. If you change the system MTU size

to a value smaller than the currently configured routing MTU size, the configuration change is accepted, but not applied

until the next switch reset. When the configuration change takes effect, the routing MTU size automatically defaults to

the new system MTU size.

Gigabit Ethernet ports are not affected by the system mtu command. Fast Ethernet ports are not affected by the system

mtu jumbo command because jumbo frames are not supported on 10/100 interfaces, including 100BASE-FX and

100BASE-BX SFP modules. If you do not configure the system mtu jumbo command, the setting of the system mtu

command applies to all Gigabit Ethernet interfaces.

You cannot set the MTU size for an individual interface; you set it for all 10/100 or all Gigabit Ethernet interfaces on the

switch. When you change the system MTU size, you must reset the switch before the new configuration takes effect. The

system mtu routing command does not require a switch reset to take effect.

Note: The system MTU setting is saved in the switch environmental variable in NVRAM and becomes effective when the

switch reloads. The MTU settings you enter with the system mtu and system mtu jumbo commands are not saved in

the switch IOS configuration file, even if you enter the copy running-config startup-config privileged EXEC command.

Therefore, if you use TFTP to configure a new switch by using a backup configuration file and want the system MTU to

be other than the default, you must explicitly configure the system mtu and system mtu jumbo settings on the new

switch and then reload the switch.

Frames sizes that can be received by the switch CPU are limited to 1998 bytes, no matter what value was entered with

the system mtu or system mtu jumbo commands. Although frames that are forwarded or routed are typically not

received by the CPU, in some cases packets are sent to the CPU, such as traffic sent to control traffic, SNMP, Telnet, or

routing protocols.

Because the switch does not fragment packets, it drops:

switched packets larger than the packet size supported on the egress interface

Configuring Interfaces

Configuring the System MTU

routed packets larger than the routing MTU value

For example, if the system mtu value is 1998 bytes and the system mtu jumbo value is 5000 bytes, packets up to 5000

bytes can be received on interfaces operating at 1000 Mbps. However, although a packet larger than 1998 bytes can be

received on an interface operating at 1000 Mbps, if its destination interface is operating at 10 or 100 Mbps, the packet

is dropped.

Routed packets are subjected to MTU checks on the sending ports. The MTU value used for routed ports is derived from

the configured system mtu value (not the system mtu jumbo value). That is, the routed MTU is never greater than the

system MTU for any VLAN. The routing protocols use the system MTU value when negotiating adjacencies and the MTU

of the link. For example, the Open Shortest Path First (OSPF) protocol uses this MTU value before setting up an adjacency

with a peer router. To view the MTU value for routed packets for a specific VLAN, use the show platform port-asic mvid

privileged EXEC command.

Note: If Layer 2 Gigabit Ethernet interfaces are configured to accept frames greater than the 10/100 interfaces, jumbo

frames received on a Layer 2 Gigabit Ethernet interface and sent on a Layer 2 10/100 interface are dropped.

Beginning in privileged EXEC mode, follow these steps to change the MTU size for all 10/100 or Gigabit Ethernet

interfaces:

Command

Purpose

configure terminal

Enter global configuration mode.

system mtu bytes

(Optional) Change the MTU size for all interfaces on the

switch that are operating at 10 or 100 Mbps. The range

is 1500 to 1998 bytes; the default is 1500 bytes.

system mtu jumbo bytes

(Optional) Change the MTU size for all Gigabit Ethernet

interfaces on the switch. The range is 1500 to 9000

bytes; the default is 1500 bytes.

system mtu routing bytes

(Optional) Change the system MTU for routed ports.

The range is 1500 to the system MTU value, the

maximum MTU that can be routed for all ports.

Although larger packets can be accepted, they cannot

be routed.

end

Return to privileged EXEC mode.

copy running-config startup-config

Save your entries in the configuration file.

reload

Reload the operating system.

If you enter a value that is outside the allowed range for the specific type of interface, the value is not accepted.

Once the switch reloads, you can verify your settings by entering the show system mtu privileged EXEC command.

This example shows how to set the maximum packet size for a Gigabit Ethernet port to 1800 bytes:

Switch(config)# system mtu jumbo 1800

Switch(config)# exit

Switch# reload

This example shows the response when you try to set Gigabit Ethernet interfaces to an out-of-range number:

Switch(config)# system mtu jumbo 25000

% Invalid input detected at '^' marker.

Configuring Interfaces

Monitoring and Maintaining the Interfaces

These sections contain interface monitoring and maintenance information:

Monitoring Interface Status, page 45

Using FEFI to Maintain the Fiber FE Interfaces, page 46

Clearing and Resetting Interfaces and Counters, page 47

Shutting Down and Restarting the Interface, page 47

Monitoring Interface Status

Commands entered at the privileged EXEC prompt display information about the interface, including the versions of the

software and the hardware, the configuration, and statistics about the interfaces. Table 8 on page 45 lists some of these

interface monitoring commands. (You can display the full list of show commands by using the show ? command at the

privileged EXEC prompt.)

Table 8

Show Commands for Interfaces

Command

Purpose

show interfaces [interface-id]

Display the status and configuration of all interfaces or a specific

interface.

show interfaces interface-id status [err-disabled]

Display interface status or a list of interfaces in an error-disabled state.

show interfaces [interface-id] switchport

Display administrative and operational status of switching mode. You

can use this command to find out if a port is in routing or in switching

mode.

show interfaces [interface-id] description

Display the description configured on an interface or all interfaces and

the interface status.

show ip interface [interface-id]

Display the usability status of all interfaces configured for IP routing or

the specified interface.

show interface [interface-id] stats

Display the input and output packets by the switching path for the

interface.

Configuring Interfaces

Monitoring and Maintaining the Interfaces

Table 8

Show Commands for Interfaces (continued)

Command

Purpose

show interfaces [interface-id] transceiver [detail |

Display these physical and operational status about an SFP module:

dom-supported-list | module number | properties

| threshold-table]

interface-id-(Optional) Display configuration and status for a

specified physical interface.

detail-(Optional) Display calibration properties, including high and

low numbers and any alarm information for any Digital Optical

Monitoring (DoM)-capable transceiver if one is installed in the

switch.

dom-supported-list-(Optional) List all supported DoM

transceivers.

module number-(Optional) Limit display to interfaces on module

on the switch. The range is 1 to 9. This option is not available if

you entered a specific interface ID.

properties-(Optional) Display speed, duplex, and inline power

settings on an interface

threshold-table-(Optional) Display alarm and warning threshold

table

show interfaces [interface-id] [{transceiver

Display physical and operational status about an SFP module.

properties | detail}] module number]

show port-type [eni | nni | uni]

Display interface type information for the Cisco ME switch.

show running-config interface [interface-id]

Display the running configuration in RAM for the interface.

show version

Display the hardware configuration, software version, the names and

sources of configuration files, and the boot images.

show controllers ethernet-controller interface-id

Display the operational state of the auto-MDIX feature on the

phy

interface.

Using FEFI to Maintain the Fiber FE Interfaces

A far end fault is an error in the link that one station detects but the other does not, such as a disconnected Tx wire. In

this example, the sending station still receives valid data and detects that the link is good through the link integrity

monitor. The sending station does not detect that its own transmission is not being received by the other station. A

100BASE-FX station that detects a remote fault like this modifies its transmitted IDLE stream to send a special bit pattern

(FEFI IDLE pattern) to inform the neighbor of the remote fault. The FEFI-IDLE pattern then triggers a shutdown of the

remote port (notconnect).

Fiber FastEthernet hardware uses far end fault indication (FEFI) to bring the link down on both sides of the link in these

situations. A similar function is provided by link negotiation for Gigabit Ethernet. FEFI is not supported on copper ports,

which do not usually have issues in which one station can detect while the other cannot. Copper ports use Ethernet link

pulses to monitor the link.

With FEFI, no forwarding loop occurs because there is no connectivity between the ports. If the link is up on one side

and down on the other, however, blackholing of traffic might occur. Use Unidirectional Link Detection (UDLD) to prevent

traffic blackholing.

Default FEFI Configuration

FEFI is enabled globally and not configurable on the switch, however it applies only to the fiber Fast Ethernet SFP

interfaces on the switch.

Configuring Interfaces

Monitoring and Maintaining the Interfaces

Using FEFI on GE SFP Ports

FEFI can be used on the switch Gigabit Ethernet (GE) SFP ports when the GE ports are connected with 100FX/LX SFP

transceiver type. However, using these SFP transceivers limits the GE interfaces to 100 MB/s.

Clearing and Resetting Interfaces and Counters

Table 9 on page 47 lists the privileged EXEC mode clear commands that you can use to clear counters and reset

interfaces.

Table 9

Clear Commands for Interfaces

Command

Purpose

clear counters [interface-id]

Clear interface counters.

clear interface interface-id

Reset the hardware logic on an interface.

clear line [number | console 0 | vty number]

Reset the hardware logic on an asynchronous serial line.

To clear the interface counters shown by the show interfaces privileged EXEC command, use the clear counters

privileged EXEC command. The clear counters command clears all current interface counters from the interface unless

you specify optional arguments that clear only a specific interface type from a specific interface number.

Note: The clear counters privileged EXEC command does not clear counters retrieved by using Simple Network

Management Protocol (SNMP), but only those seen with the show interface privileged EXEC command.

Shutting Down and Restarting the Interface

Shutting down an interface disables all functions on the specified interface and marks the interface as unavailable on all

monitoring command displays. This information is communicated to other network servers through all dynamic routing

protocols. The interface is not mentioned in any routing updates.

Beginning in privileged EXEC mode, follow these steps to shut down an interface:

Command

Purpose

configure terminal

Enter global configuration mode.

interface {vlan vlan-id} | {{fastethernet | gigabitethernet}

Select the interface to be configured.

interface-id} | {port-channel port-channel-number}

shutdown

Shut down an interface.

end

Return to privileged EXEC mode.

show running-config

Verify your entry.

Use the no shutdown interface configuration command to enable an interface.

To verify that an interface is disabled, enter the show interfaces privileged EXEC command. A disabled interface is

shown as administratively down in the display.

Configuring Switch Alarms

Information About Switch Alarms

The switch software monitors switch conditions on a per-port or a switch basis. If the conditions present on the switch

or a port do not match the set parameters, the switch software triggers an alarm or a system message. By default, the

switch software sends the system messages to a system message logging facility, or a syslog facility. You can also

configure the switch to send Simple Network Management Protocol (SNMP) traps to an SNMP server.

Global Status Monitoring Alarms

The switch processes alarms related to temperature and power supply conditions, referred to as global or facility alarms.

Table 10

Global Status Monitoring Alarms

Alarm

Description

Power supply alarm

The switch monitors dual power supply levels. If there are two power supplies installed in the

switch, an alarm triggers if a power supply fails. The alarm is automatically cleared when both

power supplies are working. You can configure the power supply alarm to be connected to the

hardware relays. For more information, see Configuring the Power Supply Alarms, page 51.

Temperature alarms

The switch contains one temperature sensor with a primary and secondary temperature setting.

The sensor monitors the environmental conditions inside the switch.

The primary and secondary temperature alarms can be set as follows:

The primary alarm is enabled automatically to trigger both at a low temperature, -4°F (-20°C)

and a high temperature, 203°F (95°C). It cannot be disabled. By default, the primary

temperature alarm is associated with the major relay.

The secondary alarm triggers when the system temperature is higher or lower than the

configured high and low temperature thresholds. The secondary alarm is disabled by default.

For more information, see Configuring the Switch Temperature Alarms, page 52.

SD-Card

By default the alarm is disabled.

FCS Error Hysteresis Threshold

The Ethernet standard calls for a maximum bit-error rate of 10^-8. The bit error-rate range is from 10^-6 to 10^-11. The bit

error-rate input to the switch is a positive exponent. If you want to configure the bit error-rate of 10^-9, enter the value 9

for the exponent. By default, the FCS bit error-rate is 10^-8.

You can set the FCS error hysteresis threshold to prevent the toggle of the alarm when the actual bit-error rate fluctuates

near the configured rate. The hysteresis threshold is defined as the ratio between the alarm clear threshold to the alarm

set threshold, expressed as a percentage value.

For example, if the FCS bit error-rate alarm value is configured to 10^-8, that value is the alarm set threshold. To set the

alarm clear threshold at 5*10^-10, the hysteresis, value h, is determined as follows:

Configuring Switch Alarms

Information About Switch Alarms

h = alarm clear threshold / alarm set threshold

h = 5*10^-10 / 10^-8 = 5*10^-2 = 0.05 = 5 percent

The FCS hysteresis threshold is applied to all ports on the switch. The allowable range is from 1 to 10 percent. The default

value is 10 percent. See Configuring the FCS Bit Error Rate Alarm, page 52 for more information.

Port Status Monitoring Alarms

The switch can also monitor the status of the Ethernet ports and generate alarm messages based on the alarms listed in

Table 11 on page 50. To save user time and effort, it supports changeable alarm configurations by using alarm profiles.

You can create a number of profiles and assign one of these profiles to each Ethernet port.

Alarm profiles provide a mechanism for you to enable or disable alarm conditions for a port and associate the alarm

conditions with one or both alarm relays. You can also use alarm profiles to set alarm conditions to send alarm traps to

an SNMP server and system messages to a syslog server. The alarm profile defaultPort is applied to all interfaces in the

factory configuration (by default).

Note: You can associate multiple alarms to one relay or one alarm to both relays.

Table 11 on page 50 lists the port status monitoring alarms and their descriptions and functions. Each fault condition is

assigned a severity level based on the Cisco IOS System Error Message Severity Level.

Table 11

Port Status Monitoring Alarms

Alarm List ID

Alarm

Description

Link Fault alarm

The switch generates a link fault alarm when problems with a port physical

layer cause unreliable data transmission. A typical link fault condition is loss

of signal or clock. The link fault alarm is cleared automatically when the link

fault condition is cleared. The severity for this alarm is error condition, level 3.

Port not Forwarding alarm

The switch generates a port not-forwarding alarm when a port is not

forwarding packets. This alarm is cleared automatically when the port begins

to forward packets. The severity for this alarm is warning, level 4.

Port not Operating alarm

The switch generates a port not-operating alarm when a port fails during the

startup self-test. When triggered, the port not-operating alarm is only cleared

when the switch is restarted and the port is operational. The severity for this

alarm is error condition, level 3.

FCS Bit Error Rate alarm

The switch generates an FCS bit error-rate alarm when the actual FCS bit

error-rate is close to the configured rate. You can set the FCS bit error-rate

by using the interface configuration CLI for each of the ports. See Configuring

the FCS Bit Error Rate Alarm, page 52 for more information. The severity for

this alarm is error condition, level 3.

Triggering Alarm Options

The switch supports these methods for triggering alarms:

Configurable Relay

The switch is equipped with one independent alarm relay that can be triggered by alarms for global, port status and

SD flash card conditions. You can configure the relay to send a fault signal to an external alarm device, such as a

bell, light, or other signaling device. You can associate any alarm condition with the alarm relay. Each fault condition

is assigned a severity level based on the Cisco IOS System Error Message Severity Level.

See Configuring the Power Supply Alarms, page 51 for more information on configuring the relay.

SNMP Traps

Configuring Switch Alarms

How to Configure Switch Alarms

SNMP is an application-layer protocol that provides a message format for communication between managers and

agents. The SNMP system consists of an SNMP manager, an SNMP agent, and a management information base

(MIB).

The snmp-server enable traps command can be changed so that the user can send alarm traps to an SNMP server.

You can use alarm profiles to set environmental or port status alarm conditions to send SNMP alarm traps. See

Enabling SNMP Traps, page 54 for more information.

Syslog Messages

You can use alarm profiles to send system messages to a syslog server. See Configuring the Power Supply Alarms,

page 51 for more information.

Default Switch Alarm Settings

Table 12

Default Switch Alarm Settings

Alarm

Default Setting

Global

Power supply alarm

Enabled in switch single power mode. No alarm.

In dual-power supply mode, the default alarm notification is a system

message to the console.

Primary temperature alarm

Enabled for switch temperature range of 203^oF (95^oC) maximum to -4°F

(-20^oC) minimum.

The primary switch temperature alarm is associated with the major relay.

Secondary temperature alarm

Disabled.

Output relay mode alarm

Normally deenergized. The alarm output has switched off or is in an off

state.

Port

Link fault alarm

Disabled on all interfaces.

Port not forwarding alarm

Disabled on all interfaces.

Port not operating alarm

Enabled on all interfaces.

FCS bit error rate alarm

Disabled on all interfaces.

How to Configure Switch Alarms

Configuring the Power Supply Alarms

Command

Purpose

configure terminal

Enters global configuration mode.

power-supply dual

Configures dual power supplies.

alarm facility power-supply disable

Disables the power supply alarm.

alarm facility power-supply relay

Associates the power supply alarm to the relay.

major

alarm facility power-supply notifies

Sends power supply alarm traps to an SNMP server.

alarm facility power-supply syslog

Sends power supply alarm traps to a syslog server.

end

Returns to privileged EXEC mode.

Configuring Switch Alarms

How to Configure Switch Alarms

Command

Purpose

show env power

Displays the switch power status.

show facility-alarm status

Displays all generated alarms for the switch.

10.

show alarm settings

Verifies the configuration.

11.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring the Switch Temperature Alarms

Command

Purpose

configure terminal

Enters global configuration mode.

alarm facility temperature {primary

Sets the high temperature threshold value. Set the threshold from -238°F

| secondary} high threshold

(-150°C) to 572°F (300°C).

alarm facility temperature primary

Sets the low temperature threshold value. Set the threshold from -328°F

low threshold

(-200°C) to 482°F (250°C).

end

Returns to privileged EXEC mode.

show alarm settings

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Associating the Temperature Alarms to a Relay

By default, the primary temperature alarm is associated to the relay. You can use the alarm facility temperature global

configuration command to associate the primary temperature alarm to an SNMP trap, or a syslog message, or to

associate the secondary temperature alarm to the relay, an SNMP trap, or a syslog message.

Note: The single relay on the switch is called the major relay.

Command

Purpose

configure terminal

Enters global configuration mode.

alarm facility temperature {primary

Associates the primary or secondary temperature alarm to the relay.

| secondary} relay major

alarm facility temperature {primary

Sends primary or secondary temperature alarm traps to an SNMP server.

| secondary} notifies

alarm facility temperature {primary

Sends primary or secondary temperature alarm traps to a syslog server.

| secondary} syslog

Uses the no alarm facility temperature secondary command to disable the

secondary temperature alarm.

end

Returns to privileged EXEC mode.

show alarm settings

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring the FCS Bit Error Rate Alarm

Setting the FCS Error Threshold

The switch generates an FCS bit error-rate alarm when the actual rate is close to the configured rate.

Configuring Switch Alarms

How to Configure Switch Alarms

Command

Purpose

configure terminal

Enters global configuration mode.

interface interface-id

Enters the interface to be configured, and enters interface configuration

mode.

fcs-threshold value

Sets the FCS error rate.

For value, the range is 6 to 11 to set a maximum bit error rate of 10^-6to 10^-11.

By default, the FCS bit error rate is 10^-8.

end

Returns to privileged EXEC mode.

show fcs-threshold

Verifies the setting.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Setting the FCS Error Hysteresis Threshold

The hysteresis setting prevents the toggle of an alarm when the actual bit error-rate fluctuates near the configured rate.

The FCS hysteresis threshold is applied to all ports of a switch.

Command

Purpose

configure terminal

Enters global configuration mode.

alarm facility fcs-hysteresis

Sets the hysteresis percentage for the switch.

percentage

For percentage, the range is 1 to 10. The default value is 10 percent.

end

Returns to privileged EXEC mode.

show running config

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring Alarm Profiles

Creating an Alarm Profile

You can use the alarm profile global configuration command to create an alarm profile or to modify an existing profile.

When you create a new alarm profile, none of the alarms are enabled.

Note: The only alarm enabled in the defaultPort profile is the Port not operating alarm.

Command

Purpose

configure terminal

Enters global configuration mode.

alarm profile name

Creates the new profile or identifies an existing profile, and enters alarm

profile configuration mode.

end

Returns to privileged EXEC mode.

show alarm profile name

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Configuring Switch Alarms

Monitoring and Maintaining Switch Alarms Status

Modifying an Alarm Profile

You can modify an alarm profile from alarm profile configuration mode.

You can enter more than one alarm type separated by a space.

Command

Purpose

alarm {fcs-error | link-fault | not-forwarding |

(Optional) Adds or modifies alarm parameters for

not-operating}

a specific alarm.

notifies {fcs-error | link-fault | not-forwarding |

(Optional) Configures the alarm to send an SNMP

not-operating}

trap to an SNMP server.

relay-major {fcs-error | link-fault |

(Optional) Configures the alarm to send an alarm

not-forwarding | not-operating}

trap to the relay.

syslog {fcs-error | link-fault | not-forwarding |

(Optional) Configures the alarm to send an alarm

not-operating}

trap to a syslog server.

Attaching an Alarm Profile to a Specific Port

Command

Purpose

configure terminal

Enters global configuration mode.

interface port interface

Enters interface configuration mode.

alarm-profile name

Attaches the specified profile to the interface.

end

Returns to privileged EXEC mode.

show alarm profile

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Enabling SNMP Traps

Command

Purpose

configure terminal

Enters global configuration mode.

snmp-server enable traps alarms

Enables the switch to send SNMP traps.

end

Returns to privileged EXEC mode.

show alarm settings

Verifies the configuration.

copy running-config startup-config

(Optional) Saves your entries in the configuration file.

Monitoring and Maintaining Switch Alarms Status

Table 13

Commands for Displaying Global and Port Alarm Status

Command

Purpose

show alarm description ports

Displays an alarm number and its text description.

show alarm profile [name]

Displays all alarm profiles in the system or a specified profile.

Configuring Switch Alarms

Configuration Examples for Switch Alarms

Table 13

Commands for Displaying Global and Port Alarm Status (continued)

Command

Purpose

show alarm settings

Displays all global alarm settings on the switch.

show env {alarm-contact | all | power |

Displays the status of environmental facilities on the switch.

temperature}

show facility-alarm status [critical | info |

Displays generated alarms on the switch.

major | minor]

Configuration Examples for Switch Alarms

Configuring External Alarms: Example

This example configures alarm input 1 named door sensor to assert a major alarm when the door circuit is closed and

then displays the status and configuration for all alarms:

Switch(config)# alarm contact 1 description door sensor

Switch(config)# alarm contact 1 severity major

Switch(config)# alarm contact 1 trigger closed

Switch(config)# end

Switch(config)# show env alarm-contact

Switch# show env alarm-contact

ALARM CONTACT 1

Status:

not asserted

Description: door sensor

Severity:

major

Trigger:

closed

ALARM CONTACT 2

Status:

not asserted

Description: external alarm contact 2

Severity:

minor

Trigger:

closed

Associating Temperature Alarms to a Relay: Examples

This example sets the secondary temperature alarm to the major relay, with a high temperature threshold value of 113^oF

(45^oC). All alarms and traps associated with this alarm are sent to a syslog server and an SNMP server.

Switch(config) # alarm facility temperature secondary high 45

Switch(config) # alarm facility temperature secondary relay major

Switch(config) # alarm facility temperature secondary syslog

Switch(config) # alarm facility temperature secondary notifies

This example sets the first (primary) temperature alarm to the major relay. All alarms and traps associated with this alarm

are sent to a syslog server.

Switch(config) # alarm facility temperature primary syslog

Switch(config) # alarm facility temperature primary relay major

Configuring a Dual Power Supply: Examples

This example shows how to configure two power supplies:

Switch# configure terminal

Configuring Switch Alarms

Configuration Examples for Switch Alarms

Switch(config)# power-supply dual

These examples show how to display information when two power supplies are not present which results in a triggered

alarm.

Switch# show facility-alarm status

Source Severity Description Relay Time

Switch MAJOR 5 Redundant Pwr missing or failed NONE Mar 01

1993 00:23:52

Switch# show env power

POWER SUPPLY A is DC OK

POWER SUPPLY B is DC FAULTY <--

Switch# show hard led

SWITCH: 1

SYSTEM: GREEN

ALARM : ALT_RED_BLACK <--

Displaying Alarm Settings: Example

Switch# show alarm settings

Alarm relay mode: De-energized

Power Supply

Alarm

Enabled

Relay

Notifies Disabled

Syslog

Enabled

Temperature-Primary

Alarm

Enabled

Thresholds MAX: 95C MIN: -20C

Relay

MAJ

Notifies Enabled

Syslog

Enabled

Temperature-Secondary

Alarm

Disabled

Threshold

Relay

Notifies Disabled

Syslog

Disabled

License-File-Corrupt

Alarm

Enabled

Relay

Notifies Enabled

Syslog

Enabled

Switch# show alarm settings

Alarm relay mode: De-energized

Power Supply

Alarm

Enabled

Relay

Notifies

Disabled

Syslog

Enabled

Temperature-Primary

Alarm

Enabled

Thresholds

MAX: 95C

MIN:

-20C

Relay

MAJ

Notifies

Enabled

Syslog

Enabled

Temperature-Secondary

Alarm

Disabled

Threshold

Relay

Configuring Switch Alarms

Additional References

Related Topic

Document Title

Alarm input and output ports.

Hardware Installation Guide Hardware Technical Guide

Standards

Title

No new or modified standards are supported by this

—

feature, and support for existing standards has not

been modified by this feature.

MIBs

MIBs Link

—

To locate and download MIBs using Cisco IOS XR software, use the

Cisco MIB Locator found at the following URL and choose a platform

under the Cisco Access Products menu:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs

Title

No new or modified RFCs are supported by this

—

feature, and support for existing RFCs has not been

modified by this feature.

Technical Assistance

Description

Link

The Cisco Technical Support website contains

http://www.cisco.com/techsupport

thousands of pages of searchable technical content,

including links to products, technologies, solutions,

technical tips, and tools. Registered Cisco.com users

can log in from this page to access even more content.

Performing Switch Setup Configuration

Restrictions for Performing Switch Setup Configuration

The DHCP-based autoconfiguration with a saved configuration process stops if there is not at least one Layer 3

interface in an up state without an assigned IP address in the network.

Unless you configure a timeout, the DHCP-based autoconfiguration with a saved configuration feature tries

indefinitely to download an IP address.

The auto-install process stops if a configuration file cannot be downloaded or it the configuration file is corrupted.

Note: The configuration file that is downloaded from TFTP is merged with the existing configuration in the running

configuration but is not saved in the NVRAM unless you enter the write memory or copy running-configuration

startup-configuration privileged EXEC command. Note that if the downloaded configuration is saved to the startup

configuration, the feature is not triggered during subsequent system restarts.

Information About Performing Switch Setup Configuration

This chapter describes how to perform your initial switch configuration tasks that include IP address assignments and

DHCP autoconfiguration.

Switch Boot Process

To start your switch, you need to follow the procedures in the Hardware Installation Guide Hardware Technical Guide for

installing and powering on the switch and for setting up the initial switch configuration (IP address, subnet mask, default

gateway, secret and Telnet passwords, and so forth).

The normal boot process involves the operation of the boot loader software, which performs these activities:

Performs low-level CPU initialization—Initializes the CPU registers, which control where physical memory is mapped,

its quantity and its speed.

Performs power-on self-test (POST) for the CPU subsystem—Tests the CPU DRAM and the portion of the flash

device that makes up the flash file system.

Initializes the flash memory card file system on the system board.

Loads a default operating system software image into memory and boots up the switch.

The boot loader provides access to the flash file system before the operating system is loaded. Normally, the boot loader

is used only to load, uncompress, and launch the operating system. After the boot loader gives the operating system

control of the CPU, the boot loader is not active until the next system reset or power-on.

The switch supports a flash memory card that makes it possible to replace a failed switch without reconfiguring the new

switch. The slot for the flash memory card is hot swappable and front-accessed. A cover protects the flash card and

holds the card firmly in place. The cover is hinged and closed with a captive screw, which prevents the card from coming

loose and protects against shock and vibration.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

Use the show flash: privileged EXEC command to display the flash memory card file settings. For information about how

to remove or replace the flash memory card on the switch, see the Hardware Installation Guide.

The boot loader also provides trap-door access into the system if the operating system has problems serious enough

that it cannot be used. The trap-door mechanism provides enough access to the system so that if it is necessary, you

can format the flash file system, reinstall the operating system software image by using the Xmodem Protocol, recover

from a lost or forgotten password, and finally restart the operating system.

Note: You can disable password recovery.

Before you can assign switch information, make sure you have connected a PC or terminal to the console port, and

configured the PC or terminal-emulation software baud rate and character format to match these of the switch console

port:

Baud rate default is 9600.

Data bits default is 8.

If the data bits option is set to 8, set the parity option to none.

Stop bits default is 1.

Parity settings default is none.

Default Switch Boot Settings

Feature

Default Setting

Operating system software image

The switch attempts to automatically boot up the system using

information in the BOOT environment variable. If the variable is not set,

the switch attempts to load and execute the first executable image it can

by performing a recursive, depth-first search throughout the flash file

system.

The Cisco IOS image is stored in a directory that has the same name as

the image file (excluding the .bin extension).

In a depth-first search of a directory, each encountered subdirectory is

completely searched before continuing the search in the original

directory.

Configuration file

Configured switches use the config.text file stored on the system board

in flash memory.

A new switch has no configuration file.

Switch Boot Optimization

The normal switch boot process involves a memory test, file system check (FSCK), and power-on self-test (POST).

The boot fast command in global configuration mode is enabled by default to permit switch boot optimization, which

disables these tests and minimizes the bootup time. However, after a system crash this feature is automatically disabled.

Note - With boot fast enabled, the expected boot time for the switch is from 2 to 3 minutes, depending on image and

configuration size.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

Reload sequences occur immediately if your switch is set up to automatically bring up the system by using information

in the BOOT environment variable. Otherwise, these reload sequences occur after you enter the manual boot command

in bootloader configuration mode.

First Reload

The switch disables the boot fast feature and displays the following warning message:

“Reloading with boot fast feature disabled”

After the system message appears, the system saves the crash information and automatically resets itself for the next

reload cycle.

Second Reload

The boot loader performs its normal full memory test and FSCK check with LED status progress. If the memory and FSCK

tests are successful, the system performs additional POST tests and the results are displayed on the console.

The boot fast feature is reenabled after the system comes up successfully.

Switch Information Assignment

You can assign IP information through the switch setup program, through a DHCP server, or manually.

Use the switch setup program if you want to be prompted for specific IP information. With this program, you can also

configure a hostname and an enable secret password. The program gives you the option of assigning a Telnet password

(to provide security during remote management) and configuring your switch as a command or member switch of a

cluster or as a standalone switch. For more information about the setup program, see the Hardware Installation Guide

Hardware Technical Guide.

Use a DHCP server for centralized control and automatic assignment of IP information after the server is configured.

Note: If you are using DHCP, do not respond to any of the questions in the setup program until the switch receives the

dynamically assigned IP address and reads the configuration file.

If you are an experienced user familiar with the switch configuration steps, manually configure the switch. Otherwise,

use the setup program.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

Switch Default Settings

Feature

Default Setting

IP address and subnet mask

No IP address or subnet mask is defined.

Default gateway

No default gateway is defined.

Enable secret password

No password is defined.

Hostname

The factory-assigned default hostname is Switch.

Telnet password

No password is defined.

Cluster command switch functionality

Disabled.

Cluster name

No cluster name is defined.

Manual boot

No.

Boot optimization

Enabled.

DHCP-Based Autoconfiguration Overview

DHCP provides configuration information to Internet hosts and internetworking devices. This protocol consists of two

components: one for delivering configuration parameters from a DHCP server to a device and a mechanism for allocating

network addresses to devices. DHCP is built on a client-server model, in which designated DHCP servers allocate

network addresses and deliver configuration parameters to dynamically configured devices. The switch can act as both

a DHCP client and a DHCP server.

During DHCP-based autoconfiguration, your switch (DHCP client) is automatically configured at startup with IP address

information and a configuration file.

With DHCP-based autoconfiguration, no DHCP client-side configuration is needed on your switch. However, you need

to configure the DHCP server for various lease options associated with IP addresses. If you are using DHCP to relay the

configuration file location on the network, you might also need to configure a Trivial File Transfer Protocol (TFTP) server

and a Domain Name System (DNS) server.

The DHCP server for your switch can be on the same LAN or on a different LAN than the switch. If the DHCP server is

running on a different LAN, you should configure a DHCP relay device between your switch and the DHCP server. A relay

device forwards broadcast traffic between two directly connected LANs. A router does not forward broadcast packets,

but it forwards packets based on the destination IP address in the received packet.

DHCP-based autoconfiguration replaces the BOOTP client functionality on your switch.

DHCP Client Request Process

When you boot up your switch, the DHCP client is invoked and requests configuration information from a DHCP server

when the configuration file is not present on the switch. If the configuration file is present and the configuration includes

the ip address dhcp interface configuration command on specific routed interfaces, the DHCP client is invoked and

requests the IP address information for those interfaces.

Figure 2 on page 63 shows the sequence of messages that are exchanged between the DHCP client and the DHCP

server.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

Figure 2

DHCP Client and Server Message Exchange

DHCPDISCOVER (broadcast)

Switch A

DHCPOFFER (unicast)

DHCP server

DHCPREQUEST (broadcast)

DHCPACK (unicast)

The client, Switch A, broadcasts a DHCPDISCOVER message to locate a DHCP server. The DHCP server offers

configuration parameters (such as an IP address, subnet mask, gateway IP address, DNS IP address, a lease for the IP

address, and so forth) to the client in a DHCPOFFER unicast message.

In a DHCPREQUEST broadcast message, the client returns a formal request for the offered configuration information to

the DHCP server. The formal request is broadcast so that all other DHCP servers that received the DHCPDISCOVER

broadcast message from the client can reclaim the IP addresses that they offered to the client.

The DHCP server confirms that the IP address has been allocated to the client by returning a DHCPACK unicast message

to the client. With this message, the client and server are bound, and the client uses configuration information received

from the server. The amount of information the switch receives depends on how you configure the DHCP serverd in

conjunction with the TFTP server. For more information, see TFTP Server, page 65.

If the configuration parameters sent to the client in the DHCPOFFER unicast message are invalid (a configuration error

exists), the client returns a DHCPDECLINE broadcast message to the DHCP server.

The DHCP server sends the client a DHCPNAK denial broadcast message, which means that the offered configuration

parameters have not been assigned, that an error has occurred during the negotiation of the parameters, or that the client

has been slow in responding to the DHCPOFFER message. (The DHCP server assigned the parameters to another client.)

A DHCP client might receive offers from multiple DHCP or BOOTP servers and can accept any of the offers; however, the

client usually accepts the first offer it receives. The offer from the DHCP server is not a guarantee that the IP address is

allocated to the switch. However, the server usually reserves the address until the client has had a chance to formally

request the address. If the switch accepts replies from a BOOTP server and configures itself, the switch broadcasts,

instead of unicasts, TFTP requests to obtain the switch configuration file.

The DHCP hostname option allows a group of switches to obtain hostnames and a standard configuration from the

central management DHCP server. A client (switch) includes in its DCHPDISCOVER message an option 12 field used to

request a hostname and other configuration parameters from the DHCP server. The configuration files on all clients are

identical except for their DHCP-obtained hostnames.

If a client has a default hostname (the hostname name global configuration command is not configured or the no

hostname global configuration command is entered to remove the hostname), the DHCP hostname option is not included

in the packet when you enter the ip address dhcp interface configuration command. In this case, if the client receives

the DCHP hostname option from the DHCP interaction while acquiring an IP address for an interface, the client accepts

the DHCP hostname option and sets the flag to show that the system now has a hostname configured.

DHCP-Based Autoconfiguration and Image Update

You can use the DHCP image upgrade features to configure a DHCP server to download both a new image and a new

configuration file to one or more switches in a network. This helps ensure that each new switch added to a network

receives the same image and configuration.

There are two types of DHCP image upgrades: DHCP autoconfiguration and DHCP auto-image update.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

DHCP Autoconfiguration

DHCP autoconfiguration downloads a configuration file to one or more switches in your network from a DHCP server. The

downloaded configuration file becomes the running configuration of the switch. It does not over write the bootup

configuration saved in the flash, until you reload the switch.

DHCP Auto-Image Update

You can use DHCP auto-image upgrade with DHCP autoconfiguration to download both a configuration and a new image

to one or more switches in your network. The switch (or switches) downloading the new configuration and the new image

can be blank (or only have a default factory configuration loaded).

If the new configuration is downloaded to a switch that already has a configuration, the downloaded configuration is

appended to the configuration file stored on the switch. (Any existing configuration is not overwritten by the downloaded

one.)

Note: To enable a DHCP auto-image update on the switch, the TFTP server where the image and configuration files are

located must be configured with the correct option 67 (the configuration filename), option 66 (the DHCP server

hostname) option 150 (the TFTP server address), and option 125 (description of the file) settings.

For procedures to configure the switch as a DHCP server, see DHCP Server Configuration Guidelines, page 64 and the

“Configuring DHCP” section of the “IP addressing and Services” section of the Cisco IOS IP DHCP Configuration Guide,

Release 15.0.

After you install the switch in your network, the auto-image update feature starts. The downloaded configuration file is

saved in the running configuration of the switch, and the new image is downloaded and installed on the switch. When

you reboot the switch, the configuration is stored in the saved configuration on the switch.

DHCP Server Configuration Guidelines

Follow these guidelines if you are configuring a device as a DHCP server:

Configure the DHCP server with reserved leases that are bound to each switch by the switch hardware address.

If you want the switch to receive IP address information, you must configure the DHCP server with these lease

options:

— IP address of the client (required)

— Subnet mask of the client (required)

— Router IP address (default gateway address to be used by the switch) (required)

— DNS server IP address (optional)

If you want the switch to receive the configuration file from a TFTP server, you must configure the DHCP server with

these lease options:

— TFTP server name (required)

— Boot filename (the name of the configuration file that the client needs) (recommended)

— Hostname (optional)

Depending on the settings of the DHCP server, the switch can receive IP address information, the configuration file,

or both.

If you do not configure the DHCP server with the lease options described previously, it replies to client requests with

only those parameters that are configured.

Performing Switch Setup Configuration

Information About Performing Switch Setup Configuration

If the IP address and the subnet mask are not in the reply, the switch is not configured. If the router IP address or

the TFTP server name are not found, the switch might send broadcast, instead of unicast, TFTP requests.

Unavailability of other lease options does not affect autoconfiguration.

The switch can act as a DHCP server. By default, the Cisco IOS DHCP server and relay agent features are enabled

on your switch but are not configured. These features are not operational. If your DHCP server is a Cisco device, for

additional information about configuring DHCP, see the “Configuring DHCP” section of the “IP Addressing and

Services” section of the Cisco IOS IP Configuration Guide on Cisco.com.

TFTP Server

Based on the DHCP server configuration, the switch attempts to download one or more configuration files from the TFTP

server. If you configured the DHCP server to respond to the switch with all the options required for IP connectivity to the

TFTP server, and if you configured the DHCP server with a TFTP server name, address, and configuration filename, the

switch attempts to download the specified configuration file from the specified TFTP server.

If you did not specify the configuration filename, the TFTP server, or if the configuration file could not be downloaded,

the switch attempts to download a configuration file by using various combinations of filenames and TFTP server

addresses. The files include the specified configuration filename (if any) and these files: network-config, cisconet.cfg,

and hostname.config (or hostname.cfg), where hostname is the switch’s current hostname. The TFTP server addresses

used include the specified TFTP server address (if any) and the broadcast address (255.255.255.255).

For the switch to successfully download a configuration file, the TFTP server must contain one or more configuration files

in its base directory. The files can include these files:

The configuration file named in the DHCP reply (the actual switch configuration file).

The network-confg or the cisconet.cfg file (known as the default configuration files).

The router-confg or the ciscortr.cfg file (These files contain commands common to all switches. Normally, if the

DHCP and TFTP servers are properly configured, these files are not accessed.)

If you specify the TFTP server name in the DHCP server-lease database, you must also configure the TFTP server

name-to-IP-address mapping in the DNS-server database.

If the TFTP server to be used is on a different LAN from the switch, or if it is to be accessed by the switch through the

broadcast address (which occurs if the DHCP server response does not contain all the required information described

previously), a relay must be configured to forward the TFTP packets to the TFTP server. For more information, see Relay

Device, page 65. The preferred solution is to configure the DHCP server with all the required information.

DNS Server

The DHCP server uses the DNS server to resolve the TFTP server name to an IP address. You must configure the TFTP

server name-to-IP address map on the DNS server. The TFTP server contains the configuration files for the switch.

You can configure the IP addresses of the DNS servers in the lease database of the DHCP server from where the DHCP

replies will retrieve them. You can enter up to two DNS server IP addresses in the lease database.

The DNS server can be on the same or on a different LAN as the switch. If it is on a different LAN, the switch must be

able to access it through a router.

Relay Device

You must configure a relay device, also referred to as a relay agent, when a switch sends broadcast packets that require

a response from a host on a different LAN. Examples of broadcast packets that the switch might send are DHCP, DNS,

and in some cases, TFTP packets. You must configure this relay device to forward received broadcast packets on an

interface to the destination host.

Cisco Industrial Ethernet 4000, 4010 and 5000 Switch Software. Configuration Guide (2022) - page 4