IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

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Information About IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

IPv6 Multiprotocol BGP Peering Using a Link-Local Address

The IPv6 multiprotocol BGP can be configured between two IPv6 devices (peers) using link-local addresses. For this function to work, you must identify the interface for the neighbor by using the neighbor update-source command, and you must configure a route map to set an IPv6 global next hop.

Boarder Gateway Protocol (BGP) uses third-party next hops for peering with multiple peers over IPv6 link-local addresses on the same interface. Peering over link-local addresses on different interfaces cannot use third party next hops. The neighbors peering using link-local addresses are split into one update group per interface. BGP splits update group membership for neighbors with link-local addresses based on the interface used to communicate with that neighbor.

How to Configure IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

Configuring an IPv6 Multiprotocol BGP Peer Using a Link-Local Address

Configuring IPv6 multiprotocol BGP between two IPv6 routers (peers) using link-local addresses requires that the interface for the neighbor be identified by using the update-source command and that a route map be configured to set an IPv6 global next hop.


Note
  • By default, neighbors that are defined using the neighbor remote-as command in router configuration mode exchange only IPv4 unicast address prefixes. To exchange other address prefix types, such as IPv6 prefixes, neighbors must also be activated using the neighbor activate command in address family configuration mode for the other prefix types, as shown for IPv6 prefixes.
  • By default, route maps that are applied in router configuration mode using the neighbor route-map command are applied to only IPv4 unicast address prefixes. Route maps for other address families must be applied in address family configuration mode using the neighbor route-map command, as shown for the IPv6 address family. The route maps are applied either as the inbound or outbound routing policy for neighbors under the specified address family. Configuring separate route maps under each address family type simplifies managing complicated or different policies for each address family.

  • The route-map used to modify the next hop needs to be applied outbound only. Inbound route-map to modify next-hop ipv6 address is not supported. Inbound route-map is supported only for IPV4 address family.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. router bgp autonomous-system-number
  4. neighbor {ip-address | ipv6-address [% ] | peer-group-name } remote-as autonomous-system-number [alternate-as autonomous-system-number ...]
  5. neighbor {ip-address | ipv6-address [% ] | peer-group-name } update-source interface-type interface-number
  6. address-family ipv6 [vrf vrf-name ] [unicast | multicast | vpnv6
  7. neighbor {ip-address | peer-group-name | ipv6-address % } activate
  8. neighbor {ip-address | peer-group-name | ipv6-address [% ]} route-map map-name {in | out
  9. exit
  10. Repeat Step 9.
  11. route-map map-tag [permit | deny ] [sequence-number ]
  12. match ipv6 address {prefix-list prefix-list-name | access-list-name
  13. set ipv6 next-hop ipv6-address [link-local-address ] [peer-address

DETAILED STEPS

  Command or Action Purpose
Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

router bgp autonomous-system-number

Example:


Device(config)# router bgp 65000

Enters router configuration mode for the specified routing process.

Step 4

neighbor {ip-address | ipv6-address [% ] | peer-group-name } remote-as autonomous-system-number [alternate-as autonomous-system-number ...]

Example:


Device(config-router)# neighbor FE80::1234:BFF:FE0E:A471% remote-as 64600

Adds the link-local IPv6 address of the neighbor in the specified remote autonomous system to the IPv6 multiprotocol BGP neighbor table of the local router.

  • The optional % keyword is the IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

Step 5

neighbor {ip-address | ipv6-address [% ] | peer-group-name } update-source interface-type interface-number

Example:


Device(config-router)# neighbor FE80::1234:BFF:FE0E:A471% update-source gigabitethernet0/0/0

Specifies the link-local address over which the peering is to occur.

  • The optional % keyword is the IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

  • If there are multiple connections to the neighbor and you do not specify the neighbor interface by using the interface-type and interface-number arguments in the neighbor update-source command, a TCP connection cannot be established with the neighbor using link-local addresses.

Step 6

address-family ipv6 [vrf vrf-name ] [unicast | multicast | vpnv6

Example:


Device(config-router)# address-family ipv6

Specifies the IPv6 address family, and enters address family configuration mode.

  • The unicast keyword specifies the IPv6 unicast address family. By default, the router is placed in configuration mode for the IPv6 unicast address family if the unicast keyword is not specified with the address-family ipv6 command.

  • The multicast keyword specifies IPv6 multicast address prefixes.

Step 7

neighbor {ip-address | peer-group-name | ipv6-address % } activate

Example:


Device(config-router-af)# neighbor FE80::1234:BFF:FE0E:A471% activate

Enables the neighbor to exchange prefixes for the IPv6 address family with the local router using the specified link-local addresses.

  • The optional % keyword is the IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

Step 8

neighbor {ip-address | peer-group-name | ipv6-address [% ]} route-map map-name {in | out

Example:


Device(config-router-af)# neighbor FE80::1234:BFF:FE0E:A471% route-map nh6 out

Applies a route map to incoming or outgoing routes.

  • The optional % keyword is the IPv6 link-local address identifier. This keyword needs to be added whenever a link-local IPv6 address is used outside the context of its interface.

Step 9

exit

Example:


Device(config-router-af)# exit

Exits address family configuration mode, and returns the device to router configuration mode.

Step 10

Repeat Step 9.

Example:


Device(config-router)# exit

Exits router configuration mode, and returns the device to global configuration mode.

Step 11

route-map map-tag [permit | deny ] [sequence-number ]

Example:


Device(config)# route-map nh6 permit 10

Defines a route map and enters route-map configuration mode.

Step 12

match ipv6 address {prefix-list prefix-list-name | access-list-name

Example:


Device(config-route-map)# match ipv6 address prefix-list cisco

Distributes any routes that have a destination IPv6 network number address permitted by a prefix list, or performs policy routing on packets.

Step 13

set ipv6 next-hop ipv6-address [link-local-address ] [peer-address

Example:


Device(config-route-map)# set ipv6 next-hop 2001:DB8::1

Overrides the next hop advertised to the peer for IPv6 packets that pass a match clause of a route map for policy routing.

  • The ipv6-address argument specifies the IPv6 global address of the next hop. It need not be an adjacent router.

  • The link-local-address argument specifies the IPv6 link-local address of the next hop. It must be an adjacent router.

Note 

The route map sets the IPv6 next-hop addresses (global and link-local) in BGP updates. If the route map is not configured, the next-hop address in the BGP updates defaults to the unspecified IPv6 address (::), which is rejected by the peer. If you specify only the global IPv6 next-hop address (the ipv6-address argument) with the set ipv6 next-hop command after specifying the neighbor interface (the interface-type argument) with the neighbor update-source command in Step 5, the link-local address of the interface specified with the interface-type argument is included as the next-hop in the BGP updates. Therefore, only one route map that sets the global IPv6 next-hop address in BGP updates is required for multiple BGP peers that use link-local addresses.

Configuration Examples for IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

Example: Configuring an IPv6 Multiprotocol BGP Peer Using a Link-Local Address

The following example configures the IPv6 multiprotocol BGP peer FE80::1234:BFF:FE0E:A471 over Gigabitethernet interface 0/0 and sets the route map named nh6 to include the IPv6 next-hop global address of Gigabitethernet interface 0/0 in BGP updates. The IPv6 next-hop link-local address can be set by the nh6 route map (not shown in the following example) or from the interface specified by the neighbor update-source command (as shown in this example). 

Device> enable
Device# configure terminal
Device(config)# router bgp 5
Device(config-router)# neighbor internal peer-group
Device(config-router)# neighbor  FE80::1234:BFF:FE0E:A471% peer-group
Device(config-router)# neighbor internal remote-as 100
Device(config-router)# neighbor FE80::1234:BFF:FE0E:A471% remote-as 64600
Device(config-router)# neighbor FE80::1234:BFF:FE0E:A471% update-source Gigabitethernet 0/0 
Device(config-router)# address-family ipv6
Device(config-router-af)# neighbor FE80::1234:BFF:FE0E:A471% activate
Device(config-router-af)# neighbor FE80::1234:BFF:FE0E:A471% route-map nh6 out
Device(config-router-af)# exit
Device(config-router)# exit
Device(config)# route-map nh6permit 10
Device(config-router-map)# match ipv6 address prefix-list cisco
Device(config-router-map)# set ipv6 next-hop 2001:DB8:526::1
Device(config-router-map)# exit
Device(config)# ipv6 prefix-list cisco permit 2001:DB8:2F22::/48 le 128
Device(config)# ipv6 prefix-list cisco deny ::/0
Device(config)# end

Note
If you specify only the global IPv6 next-hop address (the ipv6-address argument) with the set ipv6 next-hop command after specifying the neighbor interface (the interface-type argument) with the neighbor update-source command, the link-local address of the interface specified with the interface-type argument is included as the next hop in the BGP updates. Therefore, only one route map that sets the global IPv6 next-hop address in BGP updates is required for multiple BGP peers that use link-local addresses.

Additional References

Related Documents

Related Topic

Document Title

IPv6 addressing and connectivity

IPv6 Configuration Guide

Cisco IOS commands

Cisco IOS Master Command List, All Releases

IPv6 commands

Cisco IOS IPv6 Command Reference

Cisco IOS IPv6 features

Cisco IOS IPv6 Feature Mapping

Standards and RFCs

Standard/RFC

Title

RFCs for IPv6

IPv6 RFCs

MIBs

MIB

MIBs Link

—

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

Technical Assistance

Description

Link

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http://www.cisco.com/cisco/web/support/index.html

Feature Information for IPv6 Routing Multiprotocol BGP Link-Local Address Peering

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1. Feature Information for IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

Feature Name

Releases

Feature Information

IPv6 Routing: Multiprotocol BGP Link-Local Address Peering

Cisco IOS XE Release 2.1

This feature is supported.