Users Guide

BGP over unnumbered interfaces
As BGP relies on TCP for connection between peers, the interface that connects to the peer requires a unique IP address.
Assigning an IP address to every interface may exhaust the available pool of IP addresses and is error prone. Unnumbered
interfaces are the interfaces without unique IP addresses. BGP unnumbered interfaces use the extended next hop encoding
(ENHE) feature, which is defined by RFC 5549. BGP unnumbered interfaces can advertise IPv4 routes with an IPv6 next hop.
As IPv6 link-local addresses are automatically configured on connected interfaces, BGP uses these link-local addresses to form
neighborship. Unnumbered interfaces use IPv6 router advertisements to identify the address of the peer.
Restrictions
● You cannot configure VRRP for IPv6 on an unnumbered interface. This configuration causes BGP session failure.
● You cannot use the default VLAN as the unnumbered VLAN.
● Route reflectors are not supported with unnumbered peers.
● Confederations are not supported with unnumbered peers.
● Dampening is not supported with unnumbered peers.
Configure an unnumbered neighbor
To configure an unnumbered neighbor:
1. Create an interface, if required, in CONFIGURATION mode.
interface interface-type
interface interface-type — (Optional) Enter one of the following interface types:
● ethernet node/slot/port[:subport] — Display Ethernet interface information.
● port-channel id-number — Display port channel interface IDs, from 1 to 128.
● vlan vlan-id — Display the VLAN interface number, from 1 to 4093.
2. Enable RAs on the interface in INTERFACE mode.
ipv6 nd send-ra
3. Configure minimum and maximum RA intervals in INTERFACE mode.
ipv6 nd min-ra-interval 3
ipv6 nd max-ra-interval 4
4. Enable BGP on the device.
router bgp as-number
5. Enter an unnumbered neighbor in ROUTER-BGP mode.
neighbor interface interface-type
interface interface-type — (Optional) Enter one of the following interface types:
● ethernet node/slot/port[:subport] — Display Ethernet interface information.
● port-channel id-number — Display port channel interface IDs, from 1 to 128.
● vlan vlan-id — Display the VLAN interface number, from 1 to 4093.
6. Enable the BGP neighbor in ROUTER-NEIGHBOR mode.
no shutdown
Example for configuring an unnumbered neighbor
OS10(config)# interface ethernet 1/1/1
OS10(conf-if-eth1/1/1)# ipv6 nd max-ra-interval 4
OS10(conf-if-eth1/1/1)# ipv6 nd min-ra-interval 3
OS10(conf-if-eth1/1/1)# ipv6 nd send-ra
OS10(conf-if-eth1/1/1)# no shutdown
OS10(conf-if-eth1/1/1)# exit
OS10(config)# router bgp 100
Layer 3
625