HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 780

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Troubleshooting Routing
13-166
Clear the neighbor with a soft reset and see if the router begins to receive
routes. If it does, you have confirmed that the filter is the problem. Reconfigure
the prefix list or route map, keeping in mind that the router processes entries
in order by sequence number and stops as soon as it finds a match.
You can also monitor how a prefix list or route map is affecting traffic by
viewing the list or map and checking the number of packets the router has
matched to it. (See "Troubleshooting a Prefix List" on page 13-170 and "Trou-
bleshooting a Route Map" on page 13-171.)
If you are using a prefix list with a route map, then you may want to determine
whether it is the prefix list or the route map configuration that has the error.
You can configure an entry in the prefix list that permits all routes:
ProCurve(config)# ip prefix-list NeighborIn seq 100 permit 0.0.0.0/0 le 32
You can then reapply the route map to the neighbor. If the router begins to
receive routes, then you will know that you must reconfigure the prefix list.
A BGP Interface Cannot Communicate with a Neighbor. Unlike other
routing protocols, BGP interfaces do not automatically search for and
exchange routes with connected routers. You must manually configure autho-
rized neighbors.
View the BGP neighbor and double-check its IP address:
ProCurve# show ip bgp neighbors
Ping the neighbor to check connectivity.
If the ping is successful, but the router does not seem to be exchanging BGP
messages, you might need to configure eBGP multihop. External neighbors
are supposed to be directly connected to the BGP interface. If they are not,
you must specify the number of hops it is to the neighbor. For example:
ProCurve(config-bgp-neighbor)# ebgp-multihop 4
Remember that a loopback interface adds a hop to the route. Even if the
external neighbor is directly connected, you must enable eBGP multihop if
you are using the loopback interface as the source BGP interface.
You should also check the configurations shown in Table 13-27 and make sure
they match those you have agreed upon with the entity that controls the
external AS.