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L3VPN Routes on NE40E Wasn,t selected as best routes becasue MPLS LSP Issue

Publication Date:  2012-07-27 Views:  129 Downloads:  0

Issue Description

The Customer network contains many NE40E's ,all of them Runs V006R001C00.
This Network Routers deploy MPLS L3VPN to carry different kinds of traffic such as internet.
The topology is so simple PE---P--RR--PE.
The PE will send the VPNV4 routes to the RR then the RR will reflect it to other PE's .
BGP uses loopback interface as a connection interface for BGP Sessions.
Our issue is that although the PE got the VPNV4 routes from the other sites ,it didn't choose these routes as a best routes and in turn it didn't insert these routes into the vpn routing table.

Alarm Information


Handling Process

1-We have Checked the current configuration to review the L3VPN Configuration
display current
//vpn-instnace was ok
//MBGP was ok
//mpls it seems ok
  lsp-trigger ip-prefix MPLSTRIG
2-We have Checked the Routing Table :

display bgp vpnv4 vpn-instance QI routing-table

Total Number of Routes: 15

 BGP Local router ID is
 Status codes: * - valid, > - best, d - damped,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
       Network            NextHop        MED        LocPrf    PrefVal Path/Ogn
i           - public ip-                       0             100        0               ?
i                                   0          100           0               ?
i                                 0          100           0                ?
i                                 0          100           0           4761i

 3-We have checked MPLS LSP
display mpls ldp peer
// it was ok
display mpls lsp
// we didnt find lsp for VPNV4 next hop
4-We have modified ip-perfix MPLSTRIG to match the VPNV4 next hop
then display mpls lsp
// it becomes ok
5-Then we checked the vpn-instance routing table
display ip routing-table vpn-instance QI
// we found the routes and it becomes ok

Root Cause

The MBGP is the routing protocol that advertises the L3VPN routes from one PE to another PE.
The MBGP doesn't select the VPNV4 routes as best routes because of MPLS Issue,
The Route Engine must find LSP tunnel for the next hop (looback interface ) of the VPNV4 routes to be selected and inserted in the routing table.
LSP-Trigger feature controls the lsp creation ,by default the router will create lsp tunnels for all hosts (ip addreses with mask 32),
The customer used LSP-Trigger ip-perfix to control the labels and lsp tunnels that  will be asigned and created only for the matched ip-perfix ips,
but by mistake the customer created Wrong ip-perfix that prevets the router from creating lsp tunnel for VPNV4 next hop so the router didn't choose the VPNV4 routes as best and in turn didn't install it in the routing table

So we Modified the ip-perfix to match the VPNV4 next hop then the MPLS created lsp for this nexthop and then the VPNV4 routes appeared in the vpn touting table.


For MPLS L3VPN to work fine we must confirm that mpls is working fine and t assigns labels and creates lsp tunnels for loopbacks which is used as next hop for VPNV4 routes.