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IS-IS route flapping

RP/0/RSP0/CPU0:PE1# sho route 10.x.47.25
Fri Feb  2 12:00:28.308 BKK

Routing entry for 10.x.47.25/32
  Known via "isis 47", distance 114, metric 20, type level-2
  Installed Feb  2 11:57:33.751 for 00:02:54 => it's never more than 5 minutes
  Routing Descriptor Blocks, from 10.x.47.25, via Bundle-Ether11
      Route metric is 20
  No advertising protos.


RP/0/RSP0/CPU0:PE1# ping 10.x.47.25

Success rate is 0 percent (0/5)


RP/0/RSP0/CPU0:PE1# sho isi nei be11 det
Fri Feb  2 12:06:27.494 BKK

IS-IS 47 neighbors:
System Id      Interface        SNPA           State Holdtime Type IETF-NSF
PE2          BE11             *PtoP*         Up    27       L2   Capable
  Area Address(es): 49.0233
  IPv4 Address(es):*
  Topologies: 'IPv4 Unicast'
  Uptime: 01:19:45


RP/0/RSP0/CPU0:PE1# pin siz 9000 cou 9000 don int 3
Success rate is 100 percent (9000/9000), round-trip min/avg/max = 1/1/651 ms


10.x.47.25 is the loopback 0 of connected router with dark fiber. How should I do?


Thank you very much.

1 Accepted Solution

Accepted Solutions

I tried to reload another side (ASR900), it solved.


Thank you very much.

View solution in original post

4 Replies 4

paul driver
VIP Expert VIP Expert
VIP Expert


Are you aware of any physical issue, unstable links ?

Show cpu process sorted - Do you have high cpu utilization? -
Sh clns neighbors  -  no both peering rtrs
Sh logging



Please rate and mark as an accepted solution if you have found any of the information provided useful.
This then could assist others on these forums to find a valuable answer and broadens the community’s global network.

Kind Regards

Georg Pauwen
VIP Master VIP Master
VIP Master



hard to determine what causes the flapping without seeing the configurations, can you post those ? I have a feeling that it has to do with IS-IS running over an EtherChannel (which uses a lload balancing scheme that might disrupt IS-IS). 

Can you post the output of 'show interfaces x' where 'x' are the interfaces on both sides (this is to check if there are errors or dropped packets on these interfaces) ?

I tried to reload another side (ASR900), it solved.


Thank you very much.

Hello Experts,


I am doing re-design my customer network, can someone tell me how many routers we can have per IS-IS process.

How many processes, instances, routes supported by routers (ASR9K, ASR 903, ASR902, ASR901, ASR 920).

RSPs (RSP3, RSP1A and RSP2B).


I will be very thankful.


Mohammad Wasif

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