LAN loop trouble shooting.

[k_sinjish]

Hi ,

Can  anyone   please   suggest   me  any looping   trouble shooting steps.( Total  LAN  will be down – One PC  could not  access  other   PC  in other  switch( Not periodically – Twice or thrice in a week) .There  are third party  switches  as well   non Cisco  IP phone  in the setup)

1)    

         Spanning  tree  (RSTP )  , BPDU   and  root guard enabled.

2)      No indication    of   BPDUs   in the   show logs.

3)      There   is   no   much   spanning tree topology   changes.

4)      Also the  LAN  QoS   is enabled    and configured  for the Non Cisco IP phones. 

But  if I restart   all  of my  Cisco ( Only Cisco) switches  LAN   Network  will    come up   and  function   normally.

Please   suggest   me any  steps to come out   apart from enabling the   spanning tree debugs.

Regards,

Sinjish.K

[flokki123]

hi,

can you tell us a bit more of your topology please. how are things connected?

florian

[k_sinjish]

Hi florian,

Please find  the network layout in L2 perspective .

The total  network consists of 9 numbers of switches .

1) Two core swithes .(One as spanning tree root )

2) Four switches connected to the core as a star topology ( Core 2 is the secondary for the core 1)

3) RSTP and BPDU guard enabled in the switches .

4) Three switches are connected to the  core as serially ( One switch to other and terminating in the core )

Regards,

Sinjish.k

[Somasundaram Jayaraman]

Hi,

Have you checked the cpu utilization at that time?

Also if required enable port security & configure vtp pruning so that unwanted traffic flow can be avoided.

++ enable portfast with bpdu guard globally so that the removal of end device wont affect the entire vlan's mac to get flushed out.

conf t

spanning-tree port-fast default

spanning-tree bpduguard default

Hope this helps.

Cheers

Somu

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[flokki123]

when did you encounter these problems for the first time?

did it ever work fine? was something changed in the network, e.g. new devices, etc.?

do you really have to restart all of your cisco devices to make it work again?