Panasonic NN46240-710 - Manual (Page 100)

Nortel Secure Router 8000 Series
Troubleshooting - VPN___________ 3 BGP/MPLS IP VPN troubleshooting
The route is conveyed to the RM. According to the BGP next hop, the RM fixes on the iterative
next hop and the egress. If there are multiple load-balancing paths between the PE and ASBR,
BGP chooses only one path while the RM iterates multiple IGP paths. From the multiple
Interior Gateway Protocol (IGP) paths, the RM selects one path to fill out the iterative next hop
and egress.
Therefore, the BGP peer relationship cannot establish between PEs.
Troubleshooting procedure
Step 1 Use the display fib command on PE2 to check the next hop, egress, and token of the LSP tunnel
from PE2 to PE1.
Step 2 Use the display tunnel-info tunnel-id command on PE2 to check the egress and next hop of the
tunnel with an ID equal to Token, are consistent with that in the FIB.
Step 3 If the egress and next hop are not consistent, check whether load-balancing exists between the
ASBR-PE1 and the ASBR-PE2. If yes, cancel the load balancing.
Step 4 If the egress and next hop are not consistent and no load balancing occurs between the
ASBR-PE1 and the ASBR-PE2, the cause can be that the next hop of the IBGP peer
corresponds to multiple equal-cost IGP routes. Nortel recommends that you delete some links
to ensure IBGP has no equal-cost IGP routes.
—End
Summary
The BGP searching for the LDP LSP and the route iteration are two separate processes.
It is possible that the egress and the next hop of the iteration are not those of the found LDP LSP.
3.4 FAQs
Q: A BGP adjacency establishes between PEs, but private network packets cannot
forward normally. What is the problem?
A: Possible causes are:
• The loopback interface is not used to establish the BGP adjacency.
• The loopback interface is used, but its address mask is not 32-bits, and its address is not
unique in the network.
• An LSP is not set up properly between PEs.
Q: In the BGP/MPLS VPN networking of the inter-AS Option B, proper
adjacencies establish between ASBRs, but private network packets cannot
forward. What are the causes?
A: Possible causes are:
• The EBGP peer relationship between ASBRs is not set up by using the directly connected
interface.
Issue 5.3 (30 March 2009) Nortel Networks Inc. 3-21