Users Guide

If a BGP-v4 neighbor wants to carry ipv6 prefix information, it activates the IPv6 address-family. For a BGP-v6 neighbor to
carry ipv4 prefix, it activates the IPv4 address-family.
1. Enable support for the IPv6 unicast family in CONFIG-ROUTER-BGP mode.
address family ipv6 unicast
2. Enable IPv6 unicast support on a BGP neighbor/template in CONFIG-ROUTER-BGP-AF mode.
activate
Configure administrative distance
Routers use administrative distance to determine the best path between two or more routes to reach the same destination.
Administrative distance indicates the reliability of the route; the lower the administrative distance, the more reliable the route. If
the routing table manager (RTM) receives route updates from one or more routing protocols for a single destination, it chooses
the best route based on the administrative distance.
You can assign an administrative distance for the following BGP routes using the distance bgp command:
● External BGP (eBGP) routes
● Internal BGP (iBGP) routes
● Local routes
If you do not configure the administrative distance for BGP routes, the following default values are used:
● eBGP—20
● iBGP—200
● local routes—200
To change the administrative distance for BGP, use the following command:
distance bgp external-distance internal-distance local-distance
Configure administrative distance
1. Enable BGP and assign the AS number in CONFIGURATION mode, from 0.1 to 65535.65535 or 1 to 4294967295.
OS10# configure terminal
OS10(config)# router bgp 100
2. Use one of the following commands to enter the respective ADDRESS-FAMILY mode from ROUTER-BGP mode:
IPv4:
address-family ipv4 unicast
IPv6:
address-family ipv6 unicast
3. Change the administrative distance for BGP from the respective ADDRESS-FAMILY mode.
IPv4:
distance bgp 21 200 200
IPv6:
distance bgp 21 201 250
The following example provides the configuration for nondefault VRF:
OS10# configure terminal OS10(config)# router bgp 100
OS10(config-router-bgp-100)# vrf blue
OS10(config-router-bgp-100-vrf)# address-family ipv4 unicast
OS10(configure-router-bgpv4-vrf-af)# distance bgp 21 200 200
Layer 3
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