3Com Switch 7700 Configuration Manual page 181

[Switch C] interface vlan-interface 5
[Switch C-Vlan-interface5] ip address 195.1.1.2 255.255.255.0
[Switch C] ospf
[Switch C-ospf-1] area 0
[Switch C-ospf-1-area-0.0.0.0] network 193.1.1.0 0.0.0.255
[Switch C-ospf-1-area-0.0.0.0] network 195.1.1.0 0.0.0.255
[Switch C] bgp 200
[Switch C-bgp] group ex external
[Switch C-bgp] peer 193.1.1.1 group ex as-number 100
[Switch C-bgp] group in internal
[Switch C-bgp] peer 195.1.1.1 group in
4 Configure Switch D:
[Switch D] interface vlan-interface 4
[Switch D-Vlan-interface4] ip address 194.1.1.1 255.255.255.0
[Switch D] interface vlan-interface 5
[Switch D-Vlan-interface5] ip address 195.1.1.1 255.255.255.0
[Switch D] ospf
[Switch D-ospf-1] area 0
[Switch D-ospf-1-area-0.0.0.0] network 194.1.1.0 0.0.0.255
[Switch D-ospf-1-area-0.0.0.0] network 195.1.1.0 0.0.0.255
[Switch D-ospf-1-area-0.0.0.0] network 4.0.0.0 0.255.255.255
[Switch D] bgp 200
[Switch D-bgp] group ex external
[Switch D-bgp] peer ex as-number 200
[Switch D-bgp] peer 195.1.1.2 group ex
[Switch D-bgp] peer 194.1.1.2 group ex
To enable the configuration, all BGP neighbors will be reset using reset bgp all
command.
After above configuration, due to the fact that the MED attribute of route 1.0.0.0
discovered by Switch C is less than that of Switch B, Switch D will first select the
route 1.0.0.0 from Switch C.
If the MED attribute of Switch A is not configured, the local preference on Switch
C is configured as follows:
1 Add ACL 2000 on Switch C and permit network 1.0.0.0
[Switch C] acl number 2000
[Switch C-acl-basic-2000] rule permit source 1.0.0.0 0.255.255.255
2 Define the route policy with the name of localpref, of those, the local preference
matching ACL 2000 is set as 200, and that of not matching is set as 100:
[Switch C] route-policy localpref permit node 10
[Switch C-route-policy] if-match acl 2000
[Switch C-route-policy] apply local-preference 200
[Switch C-route-policy] route-policy localpref permit node 20
[Switch C-route-policy] apply local-preference 100
[Switch C-route-policy] quit
3 Apply such route policy to the BGP neighbor 193.1.1.1 (Switch A)
[Switch C] bgp 200
[Switch C-bgp] peer 193.1.1.1 route-policy localpref import
By then, due to the fact that the Local preference attribute value (200)of the route
1.0.0.0 learned by Switch C is more than that of Switch B (Switch B is not
BGP 173