Troubleshooting guide

BSR Troubleshooting Guide
8-120
Misconfigured Access List
Follow these steps to resolve access list configuration problems:
1. Use the show access-list command in Privileged EXEC mode on suspect routers
to determine if there are access lists configured and enabled on the router.
2. If there are access lists enabled on the router, disable them using the appropriate
commands. For example, to disable input access list 10, follow this command:
RDN(config)#no ip access-group 10 in
3. After disabling all access lists on the router, determine whether the missing
routing information now appears in routing tables.
4. If the information appears, it is likely that an access list is filtering traffic. To
isolate the problem access list, enable access lists one at a time until the routing
information no longer appears in the routing table.
5. Check the access list to see whether it is filtering traffic from specific TCP ports.
If an access list denies specific TCP ports, make sure that it does not deny TCP
port 179, the port BGP uses. For example, enter an explicit permit statement for
port 179 to ensure that BGP traffic is forwarded normally.
RDN(config)#ip access-list 101 permit tcp 0.0.0.0 255.255.255.255 0.0.0.0
255.255.255.255 eq 179
6. If you altered an access list, enable the list to see whether routing information can
still pass normally.
7. If routing information is no longer missing, repeat steps 1 to 6 on any other
routers in the path until all access lists are enabled and routing information
appears in the appropriate routing tables.