Hi,
I have experienced problem on an ASR 1000 router with MPLS over DMVPN, whose LDP session is flapping periodically aproximatelly every 3 minutes.
The router is a DMVPN spoke with software 3.7S4. On central site, I have an ASR 1000 DMVPN hub router with 3.7S1 software
The spoke router-id i(tied to loopback0) is 10.100.249.24, hub router-id is 10.100.255.110.
We run OSPF on the tunnel interface and the ospf neighborship is up and running - no flaps, no problems on that side.
Here are the spoke periodical logs:
012742: Dec 2 11:53:41.518 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is UP
012743: Dec 2 11:56:29.734 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is DOWN (Received error notification from peer: KeepAlive expired)
012744: Dec 2 11:56:37.534 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is UP
012745: Dec 2 11:59:32.481 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is DOWN (Received error notification from peer: KeepAlive expired)
012746: Dec 2 11:59:36.265 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (3) is UP
012747: Dec 2 12:02:34.577 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (3) is DOWN (Received error notification from peer: KeepAlive expired)
012748: Dec 2 12:02:37.831 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is UP
012749: Dec 2 12:05:37.821 MET: %LDP-5-NBRCHG: LDP Neighbor 10.100.255.110:0 (1) is DOWN (Received error notification from peer: KeepAlive expired)
.... And so on.
The central router probably really doesn't receive the LDP keepalives:
0cc1-r1#sh mpls ldp nei 10.100.249.24
Peer LDP Ident: 10.100.249.24:0; Local LDP Ident 10.100.255.110:0
TCP connection: 10.100.249.24.646 - 10.100.255.110.28800
State: Oper; Msgs sent/rcvd: 1352/2; Downstream
Up time: 00:01:03
LDP discovery sources:
Tunnel20, Src IP addr: 10.100.237.23
The strange thing is, that there are more than 27 routers (mix of 7200, ASR 1000, ISR) connected to the central site, but just this one is having problems. I have compared the configs and didn't find any difference. I tried to shut - no shut tunnel, no change in behaviour.
The strangest thing is, that the problem has dissapeared for some 3 weeks without any reason, but has reappeared after the DMVPN tunnel interface went down and up recently.
Has anyone ever experieced this as well?
What might be the cause?
Do you have any clue where to look for troubleshooting?
Thanks,
Alexander
