Other Common Bgp Problems - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Troubleshooting Routing
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When examining the route map for misconfigurations keep these tips in mind:
If you want to apply attributes to routes filtered by an inbound route map,
you must enter the set command for the attributes in the same route map
entry in which you enter the match command to select permitted routes.
If an entry does not include a match clause, then the policy in that entry
will be applied to all routes.
If you are using an entry to place a route in one or more communities (the
set clause will read community <community>), then you should enter
the send-community standard command in the BGP neighbor configu-
ration mode context.

Other Common BGP Problems

Once a BGP has opened a session and exchanged routes with neighbors, two
problems may arise:
An ISP refuses to accept the local router's routes.
Your network is flooded with external traffic.
Routes are not being defined in the correct communities.
An ISP Router Refuses Local Routes. You should verify that your ISP
allows you to advertise private routes. The ISP must support VRF.
Network Flooded with External Traffic. One of the most common uses
for BGP is BGP multihoming. BGP allows you to connect to two ISPs and
advertise certain routes to one and certain routes to the other.
An unintended consequence of multihoming is that the ISPs can advertise
routes to each other through your local network. Your private network
becomes a transit network for external traffic.
To prevent this from happening, you should configure a prefix list that adver-
tises only local subnets.
Routes in Incorrect Communities. Several causes could prevent a remote
neighbor from applying the correct policies to routes that you have defined
as members of particular communities:
You did not enable the router to send community attributes to this
neighbor.
Enter the send-community standard command from the BGP neighbor
configuration mode context.