[c-nsp] Packet Loss During the Backbone Network Converge

[Xu Hu]

Hi All,

Below is the network topology, i ping from CE-2 to CE-1, during i shutdown
the PE-4, have some packet drops.
CE connect to the backbone network using HSRP, the hear beat is through the
CE switch. PE-1 and PE-3 is the active gateway, PE-2 and PE-4 is the
standby one.

PE equipment running OSPF as IGP, then on the top having MP-iBGP, MPLS VPN,
MPLS TE auto-tunnel.

Normally i send traffic from CE-2 to CE-1 will use the path
"CE-2>PE-3>PE-1>CE-1".  The active tunnel from PE-3 to PE-1 is directly
path, the backup tunnel is path through PE-4 to PE-2 to PE-1.
So when i shutdown the router of PE-4, the active tunnel should be no
impact, but there is some packet drops. Don't understand why.

Firstly, i think it because of the HSRP, then i ping from PE-3 to CE-1
(Under vrf) when i shutdown PE-4, but the result is also have packet drops.
So i think is because of backbone network converge. But i am not sure which
part will need to converge.

   <--CE-1-->
     |          |
     |          |
     |          |
    PE-1----PE-2
     |          |
     |          |
     |          |
    PE-3----PE-4
     |          |
     |          |
     |          |
    <--CE-2-->

Will appreciate for any comments.

Best Regards,
Hu Xu