Introduction
This document explains the IPv6 Border Gateway Protocol (BGP) Local-Preference feature. Local preference is an indication to the AS about which path has preference to exit the AS in order to reach a certain network. A path with higher local preference is preferred more. The default value of preference is 100.
Requirements
Ensure that you meet these requirements before you attempt this configuration:
- Understanding of BGP routing protocol and its operation
- Understanding of IPv6 Addressing scheme
Components Used
The information in this document is tested on these software and hardware versions
- Cisco IOS Software Release 12.4, Advance IP Services Feature Set
- • Cisco 3700 Series Multi-service Access Routers
Background Information
In the example, Router R1, R2 and R3 are part of BGP Autonomous System number 123. R4 is part of Autonomous System 101 and R5 part of Autonomous System 100.
The three routers (R1, R2 and R3) are configured with OSPFv3 for IGP connectivity. IPv6 prefix of loop back interface Lo 0 (1111:111:111:A::/64 eui-64, 2222:222:222:A::/64 eui-64 And 3333:333:333:A::/64 eui-64) of all three routers is advertised in Area 0 of OSPFv3 routing protocol.
IBGP peering is formed between routers R1, R2 and R3 through learnt loopback prefixes. Router R1 and R4 are connected over a WAN link (serial connection) and forms EBGP peering. Similarly router R3 and R5 are forming EBGP peering over WAN link.
Router R4 and R5 inject the same IPv6 prefixes:
1. network BC01:BC1:10:A::/64
2. network BC02:BC1:11:A::/64
3. network BC03:BC1:12:A::/64
As the two Routers R4 and R5 inject the same IPv6 prefixes, the path selection is based on BGP well-known Attributes. In this example, Local Preference is chosen. The BGP Local Preference value of 500 is set for the prefix BC01:BC1:10:A::/64 on router R3 through route-map. This results in R3 as the exit point for this prefix and R1 the exit point for the remaining two prefixes.
Configure
The fast Ethernet interfaces (F0/0 And F0/1) of routers R1, R2 And R3 are IPv6 enabled with IPv6 address of format eui-64.
Network Diagram
This document uses this network setup:
Configurations
This document uses these configurations:
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