H3C S7500 Series Ethernet Switches Operation Manual

Operation Manual – Routing Protocol
H3C S7500 Series Ethernet Switches Chapter 6 BGP Configuration
6-32
[SwitchC-route-policy] if-match acl 2000
[SwitchC-route-policy] apply local-preference 200
[SwitchC-route-policy] quit
[SwitchC] route-policy localpref permit node 20
[SwitchC-route-policy] apply local-preference 100
[SwitchC-route-policy] quit
z Apply this routing policy to the inbound traffic flows coming from BGP neighbor
193.1.1.1 (Switch A).
[SwitchC] bgp 200
[SwitchC-bgp] peer 193.1.1.1 route-policy localpref import
In this case, because the local preference value of the route 1.0.0.0 learned by Switch
C is 200, which is greater than that of the route 1.0.0.0 learned by Switch B (Switch B
does not configure the local preference attribute, the default value is 100), Switch D
still chooses the route 1.0.0.0 coming from Switch C first.
6.10 Troubleshooting BGP Configuration
Symptom 1: A BGP neighbor relationship cannot be established; that is, the
connection with the opposite peer cannot be established.
Solution: The BGP neighbor establishment process requires using port 179 to
establish a TCP session and exchanging Open messages correctly. You can follow
these steps to solve the problem:
z Check the AS number of the neighbor.
z Check the IP address of the neighbor.
z For an EBGP neighbor not directly connected, verify that the peer
ebgp-max-hop command is used.
z Use the ping command to check the TCP connection. As a router may have
more than one interface to reach the peer, you should use the ping -a ip-address
expanded command to specify a source IP address for sending ping packets.
z If you cannot ping the neighbor device successfully, verify that there is a route to
the neighbor in the routing table.
z If you can ping the neighbor device successfully, verify that an ACL is configured
to inhibit TCP port 179. If yes, cancel the inhibition of port 179.
Symptom 2: After you use the network command to import the routes discovered by
IGP to BGP, the BGP routes cannot be successfully advertised.
Solution: For a route to be successfully imported into BGP, it is required that the route
(including the destination network segment and mask) should be consistent with a
route in the routing table. For example, a route to the network segment 10.1.1.0/24
exists in the routing table. If a route to 10.0.0.0/8 or other similar segment is imported,
an import error will occur. If OSPF is used, when you use the network command to
import a bigger network segment, the router will change the route according to the