Cisco BGP-4 Command and Configuration Handbook

3-13 bgp default local-preference local-preference

Syntax Description:

• local-preference ” Value to use as the default local preference. The range of values is 0 to 4294967295.

Purpose: Routes originating on a BGP router that are advertised within the local AS have a default local preference of 100. This command allows you to set the local preference of locally advertised routes to a value other than the default value of 100. The new value for the local preference is applicable only within the local autonomous system.

Cisco IOS Software Release: 10.0

Configuration Example: Default Local Preference

Router B in Figure 3-10 is modifying the default local preference. The value of the local preference on Router B affects only routes advertised to Router C, because Routers B and C are in the same autonomous system.

Router A interface FastEthernet0 ip address 172.17.1.2 255.255.255.0 ! router bgp 1 neighbor 172.17.1.1 remote-as 2 ___________________________________________________________________________ Router B interface Loopback0 ip address 172.16.2.1 255.255.255.0 ! interface Ethernet0/0 ip address 172.17.1.1 255.255.255.0 ! interface Serial2/0 ip address 10.1.1.1 255.255.255.252 clockrate 64000 ! router bgp 2 bgp default local-preference 75 network 172.16.2.0 mask 255.255.255.0 neighbor 10.1.1.2 remote-as 2 neighbor 172.17.1.2 remote-as 1 ___________________________________________________________________________ Router C interface Loopback0 ip address 172.16.3.1 255.255.255.0 ! interface Serial0 ip address 10.1.1.2 255.255.255.252 ! router bgp 2 network 172.16.3.0 mask 255.255.255.0 neighbor 10.1.1.1 remote-as 2

Verification

Routes advertised by Router B to Router C should have a local preference value of 75:

rtrC# show ip bgp 172.16.2.0 BGP routing table entry for 172.16.2.0/24, version 0 Paths: (1 available, no best path) Not advertised to any peer Local 10.1.1.1 from 10.1.1.1 (172.16.2.1) Origin IGP, metric 0, localpref 75, valid, internal, not synchronized, ref 2

Routes advertised by Router B to Router A should have a local preference value of 100, the default value:

rtrA# show ip bgp 172.16.2.0 BGP routing table entry for 172.16.2.0/24, version 6 continued Paths: (1 available, best #1) Not advertised to any peer 172.17.1.1 from 172.17.1.1 (172.16.2.1) Origin IGP, metric 0, localpref 100, valid, external, best, ref 2

Routes learned by Router B from Router C should also have a local preference of 100:

rtrB# show ip bgp 172.16.3.0 BGP routing table entry for 172.16.3.0/24, version 0 Paths: (1 available, no best path) Not advertised to any peer Local 10.1.1.2 from 10.1.1.2 (10.1.1.2) Origin IGP, metric 0, localpref 100, valid, internal

Troubleshooting

Step 1. Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command.

If the neighbor relationship is not in the Established state, see section 8-23.

Step 2. Verify the new local preference settings by checking the routes advertised to IBGP peers using the show ip bgp and show ip bgp prefix commands.