3Com 3C13636 Configuration Manual page 726

3Com Router 3000 Ethernet Family
Configuration Guide
[RouterD- serial 0/0/0] interface serial 0/0/1
[RouterD- serial 0/0/1] ip address 120.56.0.1 255.255.255.0
[RouterD- serial 0/0/1] interface ethernet 1/0/0
[RouterD- ethernet 1/0/0] ip address 192.168.1.1 255.255.255.0
[RouterD- ethernet 1/0/0] quit
[RouterD] bgp 100
[RouterD-bgp] network 192.168.1.0
[RouterD-bgp] group ex300 external
[RouterD-bgp] peer 172.16.1.1 group ex300 as-number 300
[RouterD-bgp] group ex200 external
[RouterD-bgp] peer 120.56.0.2 group ex200 as-number 200
[RouterD-bgp] network 192.168.1.0 mask 255.255.255.0
[RouterD-bgp] quit
[RouterD] quit
After completing the above configurations, perform the display bgp routing command
on RouterA and B, respectively. You will see that the next hop of 192.168.1.0 is
172.16.1.2, and the origin attribute is igp.
If you add as-path on RouterD:
[RouterD] bgp 100
[RouterD] peer ex300 route-policy AS300 export
[RouterD] quit
[RouterD] route-policy AS300 permit node10
[RouterD- route-policy] if-match acl 2001
[RouterD-route-policy] apply as-path 300
[RouterD- route-policy] quit
[RouterD] acl number 2001 match-order auto
[RouterD-acl-2001] rule permit ip source any
[RouterD-acl-2001] quit
[RouterD] quit
You will see that the next hop of 192.168.1.0 is changed to 10.0.0.2, with as-path being
200, 100; while the original AS300 routes are filtered out.
If you specify the IP address of the next hop on RouterA:
[RouterA] bgp 300
[RouterA] peer ex100 route-policy AS100 export
[RouterA] quit
[RouterA] route-policy AS100 permit node 10
[RouterA-route-policy] if-match acl 2001
[RouterA-route-policy] apply ip-address 10.0.0.2
[RouterA-route-policy] quit
[RouterA] acl number 3001
[RouterA-acl-3001] rule permit ip destination 192.168.1.0
Chapter 7 IP Routing Policy Configuration
3Com Corporation
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