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

Configuring Static IP Unicast Routing

Configuring Static Unicast Routes

An IP address identifies a destination for IP packets. Some IP addresses are reserved for special uses and cannot be

used for host, subnet, or network addresses. RFC 1166, “Internet Numbers,” contains the official description of these IP

addresses.

An interface can have one primary IP address. A a subnet mask identifies the bits that denote the network number in an

IP address.

This task explains how to assign an IP address and a network mask to an SVI

Command

Purpose

configure terminal

Enters global configuration mode.

interface vlan vlan_id

Enters interface configuration mode, and specifies the Layer 3

VLAN to configure.

ip address ip-address subnet-mask

Configures the IP address and IP subnet mask.

end

Returns to privileged EXEC mode.

Configuring Static Unicast Routes

Static unicast routes are user-defined routes that cause packets moving between a source and a destination to take a

specified path. Static routes can be important if the router cannot build a route to a particular destination and are useful

for specifying a gateway of last resort to which all unroutable packets are sent.

Use the no ip route prefix mask {address | interface} global configuration command to remove a static route. The switch

retains static routes until you remove them.

When an interface goes down, all static routes through that interface are removed from the IP routing table. When the

software can no longer find a valid next hop for the address specified as the forwarding router's address in a static route,

the static route is also removed from the IP routing table.

Command

Purpose

configure terminal

Enters global configuration mode.

ip route prefix mask {address | interface} [distance]

Establishs a static route.

end

Returns to privileged EXEC mode.

Monitoring and Maintaining the IP Network

Command

Description

show interfaces [interface-id]

Displays the administrative and operational status of all interface

specified interface.

Additional References for Configuring IP Unicast Routing

The following sections provide references related to switch administration:

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Configuring Static IP Unicast Routing

Additional References for Configuring IP Unicast Routing

Related Topic

Document Title

Cisco IOS basic commands

Cisco IOS Configuration Fundamentals Command Reference

Cisco IOS IP address commands

Cisco IOS IP Command Reference, Volume 1 of 3: Addressing and

Services, Release 15.0

Cisco IP routing configuration

Cisco IOS IP Routing Configuration Guides, Release 15.0

SDM template configuration

Configuring SDM Templates, page 137

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.

698

Configuring IPv6 Host Functions

This chapter describes how to configure IPv6 host functions on the switch.

Prerequisites Configuring IPv6 Host Functions

To enable dual-stack environments (supporting both IPv4 and IPv6), you must configure the switch to use the a dual

IPv4 and IPv6 switch database management (SDM) template. See Dual IPv4 and IPv6 Protocol Stacks, page 702.

Information About Configuring IPv6 Host Functions

IPv6

IPv4 users can move to IPv6 and receive services such as end-to-end security, quality of service (QoS), and globally

unique addresses. The IPv6 address space reduces the need for private addresses and Network Address Translation

(NAT) processing by border routers at network edges.

For information about how Cisco Systems implements IPv6, go to this URL:

http://www.cisco.com/en/US/products/ps6553/products_ios_technology_home.html

For information about IPv6 and other features in this chapter

See the Cisco IOS IPv6 Configuration Library at this URL:

http://www.cisco.com/en/US//docs/ios-xml/ios/ipv6/configuration/15-1mt/ipv6-15-1mt-book.html

This section describes IPv6 implementation on the switch. These sections are included:

IPv6 Addresses, page 699

Supported IPv6 Host Features, page 700

How to Configure IPv6 Hosting, page 704

IPv6 Addresses

The switch supports only IPv6 unicast addresses. It does not support site-local unicast addresses, anycast addresses,

or multicast addresses.

The IPv6 128-bit addresses are represented as a series of eight 16-bit hexadecimal fields separated by colons in the

format: n:n:n:n:n:n:n:n. This is an example of an IPv6 address:

2031:0000:130F:0000:0000:09C0:080F:130B

For easier implementation, leading zeros in each field are optional. This is the same address without leading zeros:

2031:0:130F:0:0:9C0:80F:130B

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Configuring IPv6 Host Functions

Information About Configuring IPv6 Host Functions

You can also use two colons (::) to represent successive hexadecimal fields of zeros, but you can use this short version

only once in each address:

2031:0:130F::09C0:080F:130B

For more information about IPv6 address formats, address types, and the IPv6 packet header, see the “Implementing

IPv6 Addressing and Basic Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.

In the “Implementing Addressing and Basic Connectivity” chapter, these sections apply to the switch:

IPv6 Address Formats

IPv6 Address Output Display

Simplified IPv6 Packet Header

Supported IPv6 Host Features

These sections describe the IPv6 protocol features supported by the switch:

128-Bit Wide Unicast Addresses, page 700

DNS for IPv6, page 701

ICMPv6, page 701

Neighbor Discovery, page 701

Default Router Preference, page 701

IPv6 Stateless Autoconfiguration and Duplicate Address Detection, page 701

IPv6 Applications, page 702

Dual IPv4 and IPv6 Protocol Stacks, page 702

SNMP and Syslog Over IPv6, page 703

HTTP over IPv6, page 703

Support on the switch includes expanded address capability, header format simplification, improved support of

extensions and options, and hardware parsing of the extension header. The switch supports hop-by-hop extension

header packets, which are routed or bridged in software.

128-Bit Wide Unicast Addresses

The switch supports aggregatable global unicast addresses and link-local unicast addresses. It does not support

site-local unicast addresses.

Aggregatable global unicast addresses are IPv6 addresses from the aggregatable global unicast prefix. The address

structure enables strict aggregation of routing prefixes and limits the number of routing table entries in the global

routing table. These addresses are used on links that are aggregated through organizations and eventually to the

Internet service provider.

These addresses are defined by a global routing prefix, a subnet ID, and an interface ID. Current global unicast

address allocation uses the range of addresses that start with binary value 001 (2000::/3). Addresses with a prefix

of 2000::/3(001) through E000::/3(111) must have 64-bit interface identifiers in the extended unique identifier

(EUI)-64 format.

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Configuring IPv6 Host Functions

Information About Configuring IPv6 Host Functions

Link local unicast addresses can be automatically configured on any interface by using the link-local prefix

FE80::/10(1111 1110 10) and the interface identifier in the modified EUI format. Link-local addresses are used in the

neighbor discovery protocol (NDP) and the stateless autoconfiguration process. Nodes on a local link use link-local

addresses and do not require globally unique addresses to communicate. IPv6 routers do not forward packets with

link-local source or destination addresses to other links.

For more information, see the section about IPv6 unicast addresses in the “Implementing IPv6 Addressing and Basic

Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

DNS for IPv6

IPv6 supports Domain Name System (DNS) record types in the DNS name-to-address and address-to-name lookup

processes. The DNS AAAA resource record types support IPv6 addresses and are equivalent to an A address record in

IPv4. The switch supports DNS resolution for IPv4 and IPv6.

ICMPv6

The Internet Control Message Protocol (ICMP) in IPv6 generates error messages, such as ICMP destination unreachable

messages, to report errors during processing and other diagnostic functions. In IPv6, ICMP packets are also used in the

neighbor discovery protocol and path MTU discovery.

Neighbor Discovery

The switch supports NDP for IPv6, a protocol running on top of ICMPv6, and static neighbor entries for IPv6 stations that

do not support NDP. The IPv6 neighbor discovery process uses ICMP messages and solicited-node multicast addresses

to determine the link-layer address of a neighbor on the same network (local link), to verify the reachability of the

neighbor, and to keep track of neighboring routers.

The switch supports ICMPv6 redirect for routes with mask lengths less than 64 bits. ICMP redirect is not supported for

host routes or for summarized routes with mask lengths greater than 64 bits.

Neighbor discovery throttling ensures that the switch CPU is not unnecessarily burdened while it is in the process of

obtaining the next hop forwarding information to route an IPv6 packet. The switch drops any additional IPv6 packets

whose next hop is the same neighbor that the switch is actively trying to resolve. This drop avoids further load on the

CPU.

Default Router Preference

The switch supports IPv6 default router preference (DRP), an extension in router advertisement messages. DRP improves

the ability of a host to select an appropriate router, especially when the host is multihomed and the routers are on different

links. The switch does not support the Route Information Option in RFC 4191.

An IPv6 host maintains a default router list from which it selects a router for traffic to offlink destinations. The selected

router for a destination is then cached in the destination cache. NDP for IPv6 specifies that routers that are reachable or

probably reachable are preferred over routers whose reachability is unknown or suspect. For reachable or probably

reachable routers, NDP can either select the same router every time or cycle through the router list. By using DRP, you

can configure an IPv6 host to prefer one router over another, provided both are reachable or probably reachable.

For more information about DRP for IPv6, see the “Implementing IPv6 Addresses and Basic Connectivity” chapter in the

Cisco IOS IPv6 Configuration Library on Cisco.com.

IPv6 Stateless Autoconfiguration and Duplicate Address Detection

The switch uses stateless autoconfiguration to manage link, subnet, and site addressing changes, such as management

of host and mobile IP addresses. A host autonomously configures its own link-local address, and booting nodes send

router solicitations to request router advertisements for configuring interfaces.

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Configuring IPv6 Host Functions

Information About Configuring IPv6 Host Functions

For more information about autoconfiguration and duplicate address detection, see the “Implementing IPv6 Addressing

and Basic Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.

IPv6 Applications

The switch has IPv6 support for these applications:

Ping, traceroute, Telnet, TFTP, and FTP

Secure Shell (SSH) over an IPv6 transport

HTTP server access over IPv6 transport

DNS resolver for AAAA over IPv4 transport

Cisco Discovery Protocol (CDP) support for IPv6 addresses

For more information about managing these applications, see the “Managing Cisco IOS Applications over IPv6” chapter

and the “Implementing IPv6 Addressing and Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on

Cisco.com.

Dual IPv4 and IPv6 Protocol Stacks

You must use the dual IPv4 and IPv6 template to allocate ternary content addressable memory (TCAM) usage to both

IPv4 and IPv6 protocols.

Figure 86 shows a router forwarding both IPv4 and IPv6 traffic through the same interface, based on the IP packet and

destination addresses.

Figure 86

Dual IPv4 and IPv6 Support on an Interface

IPv4

10.1.1.1

IPv6

3ffe:yyyy::1

Use the dual IPv4 and IPv6 switch database management (SDM) template to enable dual-stack environments (supporting

both IPv4 and IPv6).

The dual IPv4 and IPv6 templates allow the switch to be used in dual-stack environments.

If you try to configure IPv6 without first selecting a dual IPv4 and IPv6 template, a warning message appears.

In IPv4-only environments, the switch applies IPv4 QoS and ACLs in hardware. IPv6 packets are not supported.

In dual IPv4 and IPv6 environments, the switch applies IPv4 QoS and ACLs in hardware.

IPv6 QoS and ACLs are not supported.

If you do not plan to use IPv6, do not use the dual-stack template because this template results in less TCAM

capacity for each resource.

For more information about IPv4 and IPv6 protocol stacks, see the “Implementing IPv6 Addressing and Basic

Connectivity” chapter of Cisco IOS IPv6 Configuration Library on Cisco.com.

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Configuring IPv6 Host Functions

Information About Configuring IPv6 Host Functions

Static Routes for IPv6

Static routes are manually configured and define an explicit route between two networking devices. Static routes are

useful for smaller networks with only one path to an outside network or to provide security for certain types of traffic in

a larger network.

For more information about static routes, see the “Implementing Static Routes for IPv6” chapter in the Cisco IOS IPv6

Configuration Library on Cisco.com.

SNMP and Syslog Over IPv6

To support both IPv4 and IPv6, IPv6 network management requires both IPv6 and IPv4 transports. Syslog over IPv6

supports address data types for these transports.

SNMP and syslog over IPv6 provide these features:

Support for both IPv4 and IPv6

IPv6 transport for SNMP and to modify the SNMP agent to support traps for an IPv6 host

SNMP- and syslog-related MIBs to support IPv6 addressing

Configuration of IPv6 hosts as trap receivers

For support over IPv6, SNMP modifies the existing IP transport mapping to simultaneously support IPv4 and IPv6. These

SNMP actions support IPv6 transport management:

Opens User Datagram Protocol (UDP) SNMP socket with default settings

Provides a new transport mechanism called SR_IPV6_TRANSPORT

Sends SNMP notifications over IPv6 transport

Supports SNMP-named access lists for IPv6 transport

Supports SNMP proxy forwarding using IPv6 transport

Verifies SNMP Manager feature works with IPv6 transport

For information on SNMP over IPv6, including configuration procedures, see the “Managing Cisco IOS Applications over

IPv6” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

For information about syslog over IPv6, including configuration procedures, see the “Implementing IPv6 Addressing and

Basic Connectivity” chapter in the Cisco IOS IPv6 Configuration Library on Cisco.com.

HTTP over IPv6

The HTTP client sends requests to both IPv4 and IPv6 HTTP servers, which respond to requests from both IPv4 and IPv6

HTTP clients. URLs with literal IPv6 addresses must be specified in hexadecimal using 16-bit values between colons.

The accept socket call chooses an IPv4 or IPv6 address family. The accept socket is either an IPv4 or IPv6 socket. The

listening socket continues to listen for both IPv4 and IPv6 signals that indicate a connection. The IPv6 listening socket is

bound to an IPv6 wildcard address.

The underlying TCP/IP stack supports a dual-stack environment. HTTP relies on the TCP/IP stack and the sockets for

processing network-layer interactions.

Basic network connectivity (ping) must exist between the client and the server hosts before HTTP connections can be

made.

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Configuring IPv6 Host Functions

How to Configure IPv6 Hosting

Default IPv6 Settings

Feature

Default Setting

SDM template

Default.

IPv6 addresses

None configured.

How to Configure IPv6 Hosting

Configuring IPv6 Addressing and Enabling IPv6 Host

This section describes how to assign IPv6 addresses to individual Layer 3 interfaces and to globally forward IPv6 traffic

on the switch.

Before configuring IPv6 on the switch, consider these guidelines:

Be sure to select a dual IPv4 and IPv6 SDM template.

In the ipv6 address interface configuration command, you must enter the ipv6-address and ipv6-prefix variables

with the address specified in hexadecimal using 16-bit values between colons. The prefix-length variable (preceded

by a slash [/]) is a decimal value that shows how many of the high-order contiguous bits of the address comprise

the prefix (the network portion of the address).

To forward IPv6 traffic on an interface, you must configure a global IPv6 address on that interface. Configuring an IPv6

address on an interface automatically configures a link-local address and activates IPv6 for the interface. The configured

interface automatically joins these required multicast groups for that link:

solicited-node multicast group FF02:0:0:0:0:1:ff00::/104 for each unicast address assigned to the interface (this

address is used in the neighbor discovery process.)

all-nodes link-local multicast group FF02::1

all-routers link-local multicast group FF02::2

For more information about configuring IPv6, see the “Implementing Addressing and Basic Connectivity for IPv6” chapter

in the Cisco IOS IPv6 Configuration Library on Cisco.com.

Command

Purpose

configure terminal

Enters global configuration mode.

sdm prefer dual-ipv4-and-ipv6 default

Selects the SDM template that supports IPv4 and IPv6.

end

Returns to privileged EXEC mode.

reload

Reloads the operating system.

configure terminal

Enters global configuration mode after the switch reloads.

interface interface-id

Enters interface configuration mode, and specifies the interface

to configure.

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Configuring IPv6 Host Functions

How to Configure IPv6 Hosting

Command

Purpose

ipv6 address ipv6-prefix/prefix length eui-64

Specifies a global IPv6 address with an extended unique

identifier (EUI) in the low-order 64 bits of the IPv6 address.

Specifies only the network prefix; the last 64 bits are

automatically computed from the switch MAC address. This

enables IPv6 processing on the interface.

Specifies a link-local address on the interface to be used

ipv6 address ipv6-address link-local

instead of the link-local address that is automatically

configured when IPv6 is enabled on the interface. This

command enables IPv6 processing on the interface.

Automatically configures an IPv6 link-local address on the

interface, and enable the interface for IPv6 processing. The

link-local address can only be used to communicate with

ipv6 enable

nodes on the same link.

exit

Returns to global configuration mode.

end

Returns to privileged EXEC mode.

Configuring Default Router Preference

Router advertisement messages are sent with the default router preference (DRP) configured by the ipv6 nd

router-preference interface configuration command. If no DRP is configured, RAs are sent with a medium preference.

A DRP is useful when two routers on a link might provide equivalent, but not equal-cost routing, and policy might dictate

that hosts should prefer one of the routers.

Command

Purpose

configure terminal

Enters global configuration mode.

interface interface-id

Enters interface configuration mode, and enters the Layer 3 interface

on which you want to specify the DRP.

ipv6 nd router-preference {high |

Specifies a DRP for the router on the switch interface.

medium | low}

end

Returns to privileged EXEC mode.

Configuring IPv6 ICMP Rate Limiting

ICMP rate limiting is enabled by default with a default interval between error messages of 100 milliseconds and a bucket

size (maximum number of tokens to be stored in a bucket) of 10.

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Configuring IPv6 Host Functions

Monitoring and Maintaining IPv6 Host Information

Command

Purpose

configure terminal

Enters global configuration mode.

ipv6 icmp error-interval interval [bucketsize]

Configures the interval and bucket size for IPv6 ICMP error

messages:

interval—The interval (in milliseconds) between tokens being

added to the bucket. The range is from 0 to 2147483647

milliseconds.

bucketsize—(Optional) The maximum number of tokens

stored in the bucket. The range is from 1 to 200.

end

Returns to privileged EXEC mode.

Monitoring and Maintaining IPv6 Host Information

Command

Purpose

show ipv6 interface interface-id

Displays IPv6 interface status and configuration.

show ipv6 mtu

Displays IPv6 MTU per destination cache.

show ipv6 neighbors

Displays IPv6 neighbor cache entries.

show ipv6 prefix-list

Displays a list of IPv6 prefix lists.

show ipv6 protocols

Displays IPv6 routing protocols on the switch.

show ipv6 route

Displays the IPv6 route table entries.

show ipv6 static

Displays IPv6 static routes.

show ipv6 traffic

Displays IPv6 traffic statistics.

show ip http server history

Displays the previous 20 connections to the HTTP server, including

the IP address accessed and the time when the connection was

closed.

show ip http server connection

Displays the current connections to the HTTP server, including the

local and remote IP addresses being accessed.

show ip http client connection

Displays the configuration values for HTTP client connections to HTTP

servers.

show ip http client history

Displays a list of the last 20 requests made by the HTTP client to the

server.

Configuration Examples for IPv6 Host Functions

Enabling IPv6: Example

This example shows how to enable IPv6 with both a link-local address and a global address based on the IPv6 prefix

2001:0DB8:c18:1::/64. The EUI-64 interface ID is used in the low-order 64 bits of both addresses. Output from the show

ipv6 interface EXEC command shows how the interface ID (20B:46FF:FE2F:D940) is appended to the link-local prefix

FE80::/64 of the interface.

Switch(config)# sdm prefer dual-ipv4-and-ipv6 default

Switch(config)# interface gigabitethernetfastethernet1/0/11

Switch(config-if)# ipv6 address 2001:0DB8:c18:1::/64 eui 64

Switch(config-if)# end

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Configuring IPv6 Host Functions

Configuration Examples for IPv6 Host Functions

Switch# show ipv6 interface gigabitethernetfastethernet1/0/11

GigabitEthernetFastEthernet1/0/11 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::20B:46FF:FE2F:D940

Global unicast address(es):

2001:0DB8:c18:1:20B:46FF:FE2F:D940, subnet is 2001:0DB8:c18:1::/64 [EUI]

Joined group address(es):

FF02::1

FF02::2

FF02::1:FF2F:D940

MTU is 1500 bytes

ICMP error messages limited to one every 100 milliseconds

ICMP redirects are enabled

ND DAD is enabled, number of DAD attempts: 1

ND reachable time is 30000 milliseconds

ND advertised reachable time is 0 milliseconds

ND advertised retransmit interval is 0 milliseconds

ND router advertisements are sent every 200 seconds

ND router advertisements live for 1800 seconds

Hosts use stateless autoconfig for addresses.

Configuring DRP: Example

This example shows how to configure a DRP of high for the router on an interface.

Switch# configure terminal

Switch(config)# interface gigabitethernet1/0/1

Switch(config-if)# ipv6 nd router-preference high

Switch(config-if)# end

Configuring an IPv6 ICMP Error Message Interval

This example shows how to configure an IPv6 ICMP error message interval of 50 milliseconds and a bucket size of 20

tokens.

Switch(config)# ipv6 icmp error-interval 50 20

Displaying Show Command Output: Examples

This is an example of the output from the show ipv6 interface privileged EXEC command:

Switch# show ipv6 interface

Vlan1 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::20B:46FF:FE2F:D940

Global unicast address(es):

3FFE:C000:0:1:20B:46FF:FE2F:D940, subnet is 3FFE:C000:0:1::/64 [EUI]

Joined group address(es):

FF02::1

FF02::2

FF02::1:FF2F:D940

MTU is 1500 bytes

ICMP error messages limited to one every 100 milliseconds

ICMP redirects are enabled

ND DAD is enabled, number of DAD attempts: 1

ND reachable time is 30000 milliseconds

ND advertised reachable time is 0 milliseconds

ND advertised retransmit interval is 0 milliseconds

ND router advertisements are sent every 200 seconds

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Configuring IPv6 Host Functions

Configuration Examples for IPv6 Host Functions

ND router advertisements live for 1800 seconds

This is an example of the output from the show ipv6 protocols privileged EXEC command:

Switch# show ipv6 protocols

IPv6 Routing Protocol is “connected”

IPv6 Routing Protocol is “static”

IPv6 Routing Protocol is “rip fer”

Interfaces:

Vlan6

FastEthernet0/4

FastEthernet0/11

FastEthernet0/12

GigabitEthernet2/0/4

GigabitEthernet2/0/

GigabitEthernet1/0/12

Redistribution:

None

This is an example of the output from the show ipv6 neighbor privileged EXEC command:

Switch# show ipv6 neighbors

IPv6 Address

Age Link-layer Addr State Interface

3FFE:C000:0:7::777

- 0007.0007.0007 REACH Vl7

3FFE:C101:113:1::33

- 0000.0000.0033 REACH Fa1/0/13

This is an example of the output from the show ipv6 route privileged EXEC command:

Switch# show ipv6 route

IPv6 Routing Table - Default - 1 entries

Codes: C - Connected, L - Local, S - Static, U - Per-user Static route

FF00::/8 [0/0]

via Null0, receive

This is an example of the output from the show ipv6 traffic privileged EXEC command.

Switch# show ipv6 traffic

IPv6 statistics:

Rcvd:

1 total, 1 local destination

0 source-routed, 0 truncated

0 format errors, 0 hop count exceeded

0 bad header, 0 unknown option, 0 bad source

0 unknown protocol, 0 not a router

0 fragments, 0 total reassembled

0 reassembly timeouts, 0 reassembly failures

Sent:

36861 generated, 0 forwarded

0 fragmented into 0 fragments, 0 failed

0 encapsulation failed, 0 no route, 0 too big

0 RPF drops, 0 RPF suppressed drops

Mcast: 1 received, 36861 sent

ICMP statistics:

Rcvd: 1 input, 0 checksum errors, 0 too short

0 unknown info type, 0 unknown error type

unreach: 0 routing, 0 admin, 0 neighbor, 0 address, 0 port

parameter: 0 error, 0 header, 0 option

0 hopcount expired, 0 reassembly timeout,0 too big

0 echo request, 0 echo reply

0 group query, 0 group report, 0 group reduce

1 router solicit, 0 router advert, 0 redirects

0 neighbor solicit, 0 neighbor advert

Sent: 10112 output, 0 rate-limited

unreach: 0 routing, 0 admin, 0 neighbor, 0 address, 0 port

parameter: 0 error, 0 header, 0 option

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Configuring IPv6 Host Functions

Additional References

Related Documents, page 772

Information About Cisco’s Implementation of IP Multicast Routing

The switch supports these protocols to implement IP multicast routing:

Internet Group Management Protocol (IGMP) is used among hosts on a LAN and the routers (and multilayer switches)

on that LAN to track the multicast groups of which hosts are members.

Protocol-Independent Multicast (PIM) protocol is used among routers and multilayer switches to track which

multicast packets to forward to each other and to their directly connected LANs.

According to IPv4 multicast standards, the MAC destination multicast address begins with 0100:5e and is appended by

the last 23 bits of the IP address. On the switch, if the multicast packet does not match the switch multicast address, the

packets are treated in this way:

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Configuring IP Multicast Routing

Information About Cisco’s Implementation of IP Multicast Routing

If the packet has a multicast IP address and a unicast MAC address, the packet is forwarded in software. This can

occur because some protocols on legacy devices use unicast MAC addresses with multicast IP addresses.

If the packet has a multicast IP address and an unmatched multicast MAC address, the packet is dropped.

This section includes the following topics:

Information About IGMP, page 718

Information About PIM, page 719

Information About Source-Specific Multicast, page 723

Information About Source Specific Multicast Mapping, page 725

Information About PIM Shared Tree and Source Tree, page 726

Information About IGMP

To participate in IP multicasting, multicast hosts, routers, and multilayer switches must have the IGMP operating. This

protocol defines the querier and host roles:

A querier is a network device that sends query messages to discover which network devices are members of a given

multicast group.

A host is a receiver that sends report messages (in response to query messages) to inform a querier of a host

membership.

A set of queriers and hosts that receive multicast data streams from the same source is called a multicast group. Queriers

and hosts use IGMP messages to join and leave multicast groups.

Any host, regardless of whether it is a member of a group, can send to a group. However, only the members of a group

receive the message. Membership in a multicast group is dynamic; hosts can join and leave at any time. There is no

restriction on the location or number of members in a multicast group. A host can be a member of more than one

multicast group at a time. How active a multicast group is and what members it has can vary from group to group and

from time to time. A multicast group can be active for a long time, or it can be very short-lived. Membership in a group

can constantly change. A group that has members can have no activity.

IP multicast traffic uses group addresses, which are class D addresses. The high-order bits of a Class D address are

1110. Therefore, host group addresses can be in the range 224.0.0.0 through 239.255.255.255. Multicast addresses in

the range 224.0.0.0 to 24.0.0.255 are reserved for use by routing protocols and other network control traffic. The

address 224.0.0.0 is guaranteed not to be assigned to any group.

IGMP packets are sent using these IP multicast group addresses:

IGMP general queries are destined to the address 224.0.0.1 (all systems on a subnet).

IGMP group-specific queries are destined to the group IP address for which the switch is querying.

IGMP group membership reports are destined to the group IP address for which the switch is reporting.

IGMP Version 2 (IGMPv2) leave messages are destined to the address 224.0.0.2 (all-multicast-routers on a subnet).

In some old host IP stacks, leave messages might be destined to the group IP address rather than to the all-routers

address.

IGMP Version 1

IGMP Version 1 (IGMPv1) primarily uses a query-response model that enables the multicast router and multilayer switch

to find which multicast groups are active (have one or more hosts interested in a multicast group) on the local subnet.

IGMPv1 has other processes that enable a host to join and leave a multicast group. For more information, see RFC 1112.

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IGMP Version 2

IGMPv2 extends IGMP functionality by providing such features as the IGMP leave process to reduce leave latency,

group-specific queries, and an explicit maximum query response time. IGMPv2 also adds the capability for routers to

elect the IGMP querier without depending on the multicast protocol to perform this task. For more information, see RFC

2236.

Information About PIM

PIM is called protocol-independent: regardless of the unicast routing protocols used to populate the unicast routing

table, PIM uses this information to perform multicast forwarding instead of maintaining a separate multicast routing table.

PIM is defined in RFC 2362, Protocol-Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification. PIM is

defined in these Internet Engineering Task Force (IETF) Internet drafts:

Protocol Independent Multicast (PIM): Motivation and Architecture

Protocol Independent Multicast (PIM), Dense Mode Protocol Specification

Protocol Independent Multicast (PIM), Sparse Mode Protocol Specification

draft-ietf-idmr-igmp-v2-06.txt, Internet Group Management Protocol, Version 2

draft-ietf-pim-v2-dm-03.txt, PIM Version 2 Dense Mode

This section includes the following topics:

PIM Versions, page 719

PIM Modes, page 720

PIM Stub Routing, page 720

IGMP Helper, page 721

Auto-RP, page 721

Bootstrap Router, page 722

Multicast Forwarding and Reverse Path Check, page 722

PIM Versions

PIMv2 includes these improvements over PIMv1:

A single, active rendezvous point (RP) exists per multicast group, with multiple backup RPs. This single RP compares

to multiple active RPs for the same group in PIMv1.

A bootstrap router (BSR) provides a fault-tolerant, automated RP discovery and distribution mechanism that enables

routers and multilayer switches to dynamically learn the group-to-RP mappings.

Sparse mode and dense mode are properties of a group, as opposed to an interface. We strongly recommend

sparse-dense mode, as opposed to either sparse mode or dense mode only.

PIM join and prune messages have more flexible encoding for multiple address families.

A more flexible hello packet format replaces the query packet to encode current and future capability options.

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PIM packets are no longer inside IGMP packets; they are standalone packets.

PIM Modes

PIM can operate in dense mode (DM), sparse mode (SM), or in sparse-dense mode (PIM DM-SM), which handles both

sparse groups and dense groups at the same time.

PIM DM

PIM DM builds source-based multicast distribution trees. In dense mode, a PIM DM router or multilayer switch assumes

that all other routers or multilayer switches forward multicast packets for a group. If a PIM DM device receives a multicast

packet and has no directly connected members or PIM neighbors present, a prune message is sent back to the source

to stop unwanted multicast traffic. Subsequent multicast packets are not flooded to this router or switch on this pruned

branch because branches without receivers are pruned from the distribution tree, leaving only branches that contain

receivers.

When a new receiver on a previously pruned branch of the tree joins a multicast group, the PIM DM device detects the

new receiver and immediately sends a graft message up the distribution tree toward the source. When the upstream PIM

DM device receives the graft message, it immediately puts the interface on which the graft was received into the

forwarding state so that the multicast traffic begins flowing to the receiver.

PIM SM

PIM SM uses shared trees and shortest-path-trees (SPTs) to distribute multicast traffic to multicast receivers in the

network. In PIM SM, a router or multilayer switch assumes that other routers or switches do not forward multicast packets

for a group, unless there is an explicit request for the traffic (join message). When a host joins a multicast group using

IGMP, its directly connected PIM SM device sends PIM join messages toward the root, also known as the RP. This join

message travels router-by-router toward the root, constructing a branch of the shared tree as it goes.

The RP keeps track of multicast receivers. It also registers sources through register messages received from the source’s

first-hop router (designated router [DR]) to complete the shared tree path from the source to the receiver. When using a

shared tree, sources must send their traffic to the RP so that the traffic reaches all receivers.

Prune messages are sent up the distribution tree to prune multicast group traffic. This action permits branches of the

shared tree or SPT that were created with explicit join messages to be torn down when they are no longer needed.

PIM Stub Routing

The PIM stub routing feature reduces resource usage by moving routed traffic closer to the end user.

In a network using PIM stub routing, the only allowable route for IP traffic to the user is through a switch that is configured

with PIM stub routing. PIM passive interfaces are connected to Layer 2 access domains, such as VLANs, or to interfaces

that are connected to other Layer 2 devices. Only directly connected multicast (IGMP) receivers and sources are allowed

in the Layer 2 access domains. The PIM passive interfaces do not send or process any received PIM control packets.

When using PIM stub routing, you should configure the distribution and remote routers to use IP multicast routing and

configure only the switch as a PIM stub router. The switch does not route transit traffic between distribution routers. You

also need to configure a routed uplink port on the switch. The switch uplink port cannot be used with SVIs. If you need

PIM for an SVI uplink port, you should upgrade to the IP services feature set.

You must also configure EIGRP stub routing when configuring PIM stub routing on the switch.

The redundant PIM stub router topology is not supported. The redundant topology exists when there is more than one

PIM router forwarding multicast traffic to a single access domain. PIM messages are blocked, and the PIM assert and

designated router election mechanisms are not supported on the PIM passive interfaces. Only the nonredundant access

router topology is supported by the PIM stub feature. By using a nonredundant topology, the PIM passive interface

assumes that it is the only interface and designated router on that access domain.

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In Figure 88 on page 721, Switch A routed uplink port 25 is connected to the router and PIM stub routing is enabled on

the VLAN 100 interfaces and on Host 3. This configuration allows the directly connected hosts to receive traffic from

multicast source 200.1.1.3. See Configuring PIM Stub Routing, page 733 for more information.

Figure 88

PIM Stub Router Configuration

Switch

3.1.1.2.255.255.255.0

Port 25

Port 20

Source

Router

200.1.1.3

VLAN 100

Host 3

Host 1

Host 2

IGMP Helper

PIM stub routing moves routed traffic closer to the end user and reduces network traffic. You can also reduce traffic by

configuring a stub router (switch) with the IGMP helper feature.

You can configure a stub router (switch) with the igmp helper help-address interface configuration command to enable

the switch to send reports to the next-hop interface. Hosts that are not directly connected to a downstream router can

then join a multicast group sourced from an upstream network. The IGMP packets from a host wanting to join a multicast

stream are forwarded upstream to the next-hop device when this feature is configured. When the upstream central router

receives the helper IGMP reports or leaves, it adds or removes the interfaces from its outgoing interface list for that group.

For complete syntax and usage information for the ip igmp helper-address command, see the Cisco IOS IP Multicast

Command Reference.

Auto-RP

This proprietary feature eliminates the need to manually configure the RP information in every router and multilayer switch

in the network. For Auto-RP to work, you configure a Cisco router or multilayer switch as the mapping agent. It uses IP

multicast to learn which routers or switches in the network are possible candidate RPs to receive candidate RP

announcements. Candidate RPs periodically send multicast RP-announce messages to a particular group or group range

to announce their availability.

Mapping agents listen to these candidate RP announcements and use the information to create entries in their

Group-to-RP mapping caches. Only one mapping cache entry is created for any Group-to-RP range received, even if

multiple candidate RPs are sending RP announcements for the same range. As the RP-announce messages arrive, the

mapping agent selects the router or switch with the highest IP address as the active RP and stores this RP address in the

Group-to-RP mapping cache.

Mapping agents periodically multicast the contents of their Group-to-RP mapping cache. Thus, all routers and switches

automatically discover which RP to use for the groups they support. If a router or switch fails to receive RP-discovery

messages and the Group-to-RP mapping information expires, it switches to a statically configured RP that was defined

with the ip pim rp-address global configuration command. If no statically configured RP exists, the router or switch

changes the group to dense-mode operation.

Multiple RPs serve different group ranges or serve as hot backups of each other.

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Bootstrap Router

PIMv2 BSR is another method to distribute group-to-RP mapping information to all PIM routers and multilayer switches

in the network. It eliminates the need to manually configure RP information in every router and switch in the network.

However, instead of using IP multicast to distribute group-to-RP mapping information, BSR uses hop-by-hop flooding

of special BSR messages to distribute the mapping information.

The BSR is elected from a set of candidate routers and switches in the domain that have been configured to function as

BSRs. The election mechanism is similar to the root-bridge election mechanism used in bridged LANs. The BSR election

is based on the BSR priority of the device contained in the BSR messages that are sent hop-by-hop through the network.

Each BSR device examines the message and forwards out all interfaces only the message that has either a higher BSR

priority than its BSR priority or the same BSR priority, but with a higher BSR IP address. Using this method, the BSR is

elected.

The elected BSR sends BSR messages with a TTL of 1. Neighboring PIMv2 routers or multilayer switches receive the

BSR message and multicast it out all other interfaces (except the one on which it was received) with a TTL of 1. In this

way, BSR messages travel hop-by-hop throughout the PIM domain. Because BSR messages contain the IP address of

the current BSR, the flooding mechanism enables candidate RPs to automatically learn which device is the elected BSR.

Candidate RPs send candidate RP advertisements showing the group range for which they are responsible to the BSR,

which stores this information in its local candidate-RP cache. The BSR periodically advertises the contents of this cache

in BSR messages to all other PIM devices in the domain. These messages travel hop-by-hop through the network to all

routers and switches, which store the RP information in the BSR message in their local RP cache. The routers and

switches select the same RP for a given group because they all use a common RP hashing algorithm.

Multicast Forwarding and Reverse Path Check

With unicast routing, routers and multilayer switches forward traffic through the network along a single path from the

source to the destination host whose IP address appears in the destination address field of the IP packet. Each router

and switch along the way makes a unicast forwarding decision, using the destination IP address in the packet, by looking

up the destination address in the unicast routing table and forwarding the packet through the specified interface to the

next hop toward the destination.

With multicasting, the source is sending traffic to an arbitrary group of hosts represented by a multicast group address

in the destination address field of the IP packet. To decide whether to forward or drop an incoming multicast packet, the

router or multilayer switch uses a reverse path forwarding (RPF) check on the packet as follows and shown in Figure 89

on page 723:

1. The router or multilayer switch examines the source address of the arriving multicast packet to decide whether the

packet arrived on an interface that is on the reverse path back to the source.

2. If the packet arrives on the interface leading back to the source, the RPF check is successful and the packet is

forwarded to all interfaces in the outgoing interface list (which might not be all interfaces on the router).

3. If the RPF check fails, the packet is discarded.

Some multicast routing protocols maintain a separate multicast routing table and use it for the RPF check. However, PIM

uses the unicast routing table to perform the RPF check.

Figure 89 on page 723 shows port 2 receiving a multicast packet from source 151.10.3.21. Table 1 shows that the port

on the reverse path to the source is port 1, not port 2. Because the RPF check fails, the multilayer switch discards the

packet. Another multicast packet from source 151.10.3.21 is received on port 1, and the routing table shows this port is

on the reverse path to the source. Because the RPF check passes, the switch forwards the packet to all ports in the

outgoing port list.

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Figure 89

RPF Check

Multicast

packet from

source 151.10.3.21

is forwarded.

packet is discarded.

Gigabit Ethernet 0/1

Gigabit Ethernet 0/2

Layer 3 switch

Fast Ethernet 0/1

Fast Ethernet 0/2

Network

Port

151.10.0.0/16

Gigabit Ethernet 0/1

198.14.32.0/32

Fast Ethernet 0/1

204.1.16.0/24

Fast Ethernet 0/2

PIM uses both source trees and RP-rooted shared trees to forward datagrams (described in the PIM DM, page 720 and

the PIM SM, page 720). The RPF check is performed differently for each:

If a PIM router or multilayer switch has a source-tree state (that is, an (S,G) entry is present in the multicast routing

table), it performs the RPF check against the IP address of the source of the multicast packet.

If a PIM router or multilayer switch has a shared-tree state (and no explicit source-tree state), it performs the RPF

check on the RP address (which is known when members join the group).

Sparse-mode PIM uses the RPF lookup function to decide where it needs to send joins and prunes:

(S,G) joins (which are source-tree states) are sent toward the source.

(*,G) joins (which are shared-tree states) are sent toward the RP.

Dense-mode PIM uses only source trees and uses RPF as previously described.

Information About Source-Specific Multicast

The Source-Specific Multicast (SSM) feature is an extension of IP multicast in which datagram traffic is forwarded to

receivers from only those multicast sources that the receivers have explicitly joined. For multicast groups configured for

SSM, only SSM distribution trees (no shared trees) are created.

SSM Components Overview

SSM is a datagram delivery model that best supports one-to-many applications, also known as broadcast applications.

SSM is a core networking technology for the Cisco implementation of IP multicast solutions targeted for audio and video

broadcast application environments. The switch supports these components that support the implementation of SSM:

Protocol independent multicast source-specific mode (PIM-SSM)

PIM-SSM is the routing protocol that supports the implementation of SSM and is derived from PIM sparse mode

(PIM-SM).

Internet Group Management Protocol version 3 (IGMPv3)

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To run SSM with IGMPv3, SSM must be supported in the Cisco IOS router, the host where the application is running,

and the application itself.

How SSM Differs from Internet Standard Multicast

The current IP multicast infrastructure in the Internet and many enterprise intranets is based on the PIM-SM protocol and

Multicast Source Discovery Protocol (MSDP). These protocols have the limitations of the Internet Standard Multicast

(ISM) service model. For example, with ISM, the network must maintain knowledge about which hosts in the network are

actively sending multicast traffic.

The ISM service consists of the delivery of IP datagrams from any source to a group of receivers called the multicast host

group. The datagram traffic for the multicast host group consists of datagrams with an arbitrary IP unicast source address

S and the multicast group address G as the IP destination address. Systems receive this traffic by becoming members

of the host group.

Membership in a host group simply requires signalling the host group through IGMP version 1, 2, or 3. In SSM, delivery

of datagrams is based on (S, G) channels. In both SSM and ISM, no signalling is required to become a source. However,

in SSM, receivers must subscribe or unsubscribe to (S, G) channels to receive or not receive traffic from specific sources.

In other words, receivers can receive traffic only from (S, G) channels to which they are subscribed, whereas in ISM,

receivers need not know the IP addresses of sources from which they receive their traffic. The proposed standard

approach for channel subscription signalling use IGMP include mode membership reports, which are supported only in

IGMP version 3.

SSM IP Address Range

SSM can coexist with the ISM service by applying the SSM delivery model to a configured subset of the IP multicast

group address range. Cisco IOS software allows SSM configuration for the IP multicast address range of 224.0.0.0

through 239.255.255.255. When an SSM range is defined, existing IP multicast receiver applications do not receive any

traffic when they try to use an address in the SSM range (unless the application is modified to use an explicit (S, G)

channel subscription).

SSM Operations

An established network, in which IP multicast service is based on PIM-SM, can support SSM services. SSM can also be

deployed alone in a network without the full range of protocols that are required for interdomain PIM-SM (for example,

MSDP, Auto-RP, or bootstrap router [BSR]) if only SSM service is needed.

If SSM is deployed in a network already configured for PIM-SM, only the last-hop routers support SSM. Routers that are

not directly connected to receivers do not require support for SSM. In general, these not-last-hop routers must only run

PIM-SM in the SSM range and might need additional access control configuration to suppress MSDP signalling,

registering, or PIM-SM shared tree operations from occurring within the SSM range.

Use the ip pim ssm global configuration command to configure the SSM range and to enable SSM. This configuration

has the following effects:

For groups within the SSM range, (S, G) channel subscriptions are accepted through IGMPv3 include-mode

membership reports.

PIM operations within the SSM range of addresses change to PIM-SSM, a mode derived from PIM-SM. In this mode,

only PIM (S, G) join and prune messages are generated by the router, and no (S, G) rendezvous point tree (RPT) or

(*, G) RPT messages are generated. Incoming messages related to RPT operations are ignored or rejected, and

incoming PIM register messages are immediately answered with register-stop messages. PIM-SSM is

backward-compatible with PIM-SM unless a router is a last-hop router. Therefore, routers that are not last-hop

routers can run PIM-SM for SSM groups (for example, if they do not yet support SSM).

No MSDP source-active (SA) messages within the SSM range are accepted, generated, or forwarded.

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IGMPv3 Host Signalling

In IGMPv3, hosts signal membership to last hop routers of multicast groups. Hosts can signal group membership with

filtering capabilities with respect to sources. A host can either signal that it wants to receive traffic from all sources

sending to a group except for some specific sources (called exclude mode), or that it wants to receive traffic only from

some specific sources sending to the group (called include mode).

IGMPv3 can operate with both ISM and SSM. In ISM, both exclude and include mode reports are applicable. In SSM, only

include mode reports are accepted by the last-hop router. Exclude mode reports are ignored.

Information About Source Specific Multicast Mapping

The Source Specific Multicast (SSM) mapping feature supports SSM transition when supporting SSM on the end system

is impossible or unwanted due to administrative or technical reasons. You can use SSM mapping to leverage SSM for

video delivery to legacy STBs that do not support IGMPv3 or for applications that do not use the IGMPv3 host stack.

In a typical STB deployment, each TV channel uses one separate IP multicast group and has one active server host

sending the TV channel. A single server can send multiple TV channels, but each to a different group. In this network

environment, if a router receives an IGMPv1 or IGMPv2 membership report for a particular group, the report addresses

the well-known TV server for the TV channel associated with the multicast group.

When SSM mapping is configured, if a router receives an IGMPv1 or IGMPv2 membership report for a particular group,

the router translates this report into one or more channel memberships for the well-known sources associated with this

group.

When the router receives an IGMPv1 or IGMPv2 membership report for a group, the router uses SSM mapping to

determine one or more source IP addresses for the group. SSM mapping then translates the membership report as an

IGMPv3 report and continues as if it had received an IGMPv3 report. The router then sends PIM joins and continues to

be joined to these groups as long as it continues to receive the IGMPv1 or IGMPv2 membership reports, and the SSM

mapping for the group remains the same.

SSM mapping enables the last hop router to determine the source addresses either by a statically configured table on

the router or through a DNS server. When the statically configured table or the DNS mapping changes, the router leaves

the current sources associated with the joined groups.

Static SSM Mapping

With static SSM mapping, you can configure the last hop router to use a static map to determine the sources that are

sending to groups. Static SSM mapping requires that you configure ACLs to define group ranges. Then you can map the

groups permitted by those ACLs to sources by using the ip igmp static ssm-map global configuration command.

You can configure static SSM mapping in smaller networks when a DNS is not needed or to locally override DNS

mappings. When configured, static SSM mappings take precedence over DNS mappings.

DNS-Based SSM Mapping

You can use DNS-based SSM mapping to configure the last hop router to perform a reverse DNS lookup to determine

sources sending to groups. When DNS-based SSM mapping is configured, the router constructs a domain name that

includes the group address and performs a reverse lookup into the DNS. The router looks up IP address resource records

and uses them as the source addresses associated with this group. SSM mapping supports up to 20 sources for each

group. The router joins all sources configured for a group (see Figure 90 on page 726).

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Figure 90

DNS-Based SSM-Mapping

Source

(S, G) Join

DNS response

DNS server

Reverse DNS lookup

IGMPv2 membership report

STB host 1

STB host 2

STB host 3

The SSM mapping mechanism that enables the last hop router to join multiple sources for a group can provide source

redundancy for a TV broadcast. In this context, the last hop router provides redundancy using SSM mapping to

simultaneously join two video sources for the same TV channel. However, to prevent the last hop router from duplicating

the video traffic, the video sources must use a server-side switchover mechanism. One video source is active, and the

other backup video source is passive. The passive source waits until an active source failure is detected before sending

the video traffic for the TV channel. Thus, the server-side switchover mechanism ensures that only one of the servers is

actively sending video traffic for the TV channel.

To look up one or more source addresses for a group that includes G1, G2, G3, and G4, you must configure these DNS

records on the DNS server:

G4.G3.G2.G1 [multicast-domain] [timeout]IN A source-address-1

IN A source-address-2

IN A source-address-n

Refer to your DNS server documentation for more information about configuring DNS resource records.

Information About PIM Shared Tree and Source Tree

By default, members of a group receive data from senders to the group across a single data-distribution tree rooted at

the RP. Figure 91 on page 727 shows this type of shared-distribution tree. Data from senders is delivered to the RP for

distribution to group members joined to the shared tree.

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