ISIS Sporadically failing over SRP ring

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Jul 16th, 2010
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Hi All.


I have a customer who has there own private SRP ring using IS-IS as the IGP and TDP for the MPLS protocol.


Every now and then the IS-IS loses its adjacencys with the some of the routers on the ring.  This also happens with TDP.  Log messages for IS-IS below:



Jul 13 12:17:47.725 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6736 (SRP1/1) Down, hold time expired
Jul 13 12:17:48.725 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6736 (SRP1/1) Up, new adjacency
Jul 14 01:11:33.412 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6741 (SRP1/1) Down, neighbor forgot us
Jul 14 01:11:34.412 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6741 (SRP1/1) Up, new adjacency
Jul 14 08:16:52.117 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6750 (SRP1/1) Down, hold time expired
Jul 14 08:16:53.117 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6750 (SRP1/1) Up, new adjacency
Jul 14 16:07:11.178 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Down, hold time expired
Jul 14 16:07:12.178 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Up, new adjacency
Jul 15 15:29:08.170 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Down, hold time expired
Jul 15 15:29:09.170 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Up, new adjacency
Jul 15 21:51:33.520 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Down, hold time expired
Jul 15 21:51:34.520 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6747 (SRP1/1) Up, new adjacency
.Jul 16 01:20:53.202 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6750 (SRP1/1) Down, hold time expired
.Jul 16 01:20:54.198 BST: %CLNS-5-ADJCHANGE: ISIS: Adjacency to GM6750 (SRP1/1) Up, new adjacency


The weird thing is this happens for just a second and then it recovers.


TDP log message below:


Jul 14 03:59:13.806 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.142:0 is DOWN
Jul 14 03:59:18.498 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.142:0 is UP
Jul 14 16:19:53.448 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.142:0 is DOWN
Jul 14 16:19:54.664 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.142:0 is UP
Jul 14 17:51:22.028 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.128:0 is DOWN
Jul 14 17:51:26.080 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.128:0 is UP
.Jul 16 06:44:14.712 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.128:0 is DOWN
.Jul 16 06:44:22.464 BST: %LDP-5-NBRCHG: TDP Neighbor 145.233.101.128:0 is UP


show isis neighbors below:


System Id      Interface   SNPA                State  Holdtime  Type Protocol
GM6744         SR1/1       0009.7c21.4b80      Up     21        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 1w2d
  NSF capable
GM6750         SR1/1       000a.b7b6.9b80      Up     23        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 07:19:47
  NSF capable
GM6747         SR1/1       000a.b7b6.ab80      Up     23        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 10:49:06
  NSF capable
GM6736         SR1/1       0009.7cf9.6a00      Up     27        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 2d20h
  NSF capable
GM6741         SR1/1       0009.7c49.cc00      Up     22        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 2d07h
  NSF capable
GM6740         SR1/1       0009.7c49.cc80      Up     27        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 1y51w


System Id      Interface   SNPA                State  Holdtime  Type Protocol
  NSF capable
GM6738         SR1/1       0009.b775.3880      Up     27        L2   IS-IS
  Area Address(es): 49.0001
  IP Address(es): 
  Uptime: 3d04h
  NSF capable



show tdp neighbor below:



GM6749#sh tag-switching tdp neighbor | i Up
        Up time: 1y18w
        Up time: 2w0d
        Up time: 2w0d
        Up time: 4d06h
        Up time: 2d12h
        Up time: 1d16h
        Up time: 01:57:43




I'm a bit puzzled why the adjacencys are failing as the holdtimer is set to 30 secs.



Thanks for the help.


Cheers


Kev

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rajivrajan1 Mon, 07/19/2010 - 04:21
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is this filtered log w r t ISIS or the complete one , is there any other physical lay

er issues possibly ?

Giuseppe Larosa Wed, 07/21/2010 - 13:19
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Hello Kevin,

ISIS hello packets are padded to CLNS MTU with default settings this is different from what happens with OSPF hello packets that are small packets.


Also ISIS packets are not IP packets so if any form of scheduler is used on the SRP ring there is the risk ISIS packets are not treated well


you could try to reduce clns mtu in interface mode and to disable hello padding (not sure if this is done in router isis process or interface level)


Hope to help

Giuseppe

kevinhobson2000 Fri, 07/23/2010 - 02:02
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Guisar,


Thanks for the advice.


I forgot to add that TDP also loses its neighbors as well.


More frequently than ISIS.


There is a QOS policy on the SRP interface so there is a scheduler active.


I had already disabled hello padding.


Thanks


Kev

kevinhobson2000 Fri, 07/23/2010 - 02:28
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To add.


Dont IGP's use the pak priority so they always go before anything else?


Cheers


Kev

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