8600 & STG Groups

[KennyLamb]

Hello,
We are having an issue whereby we have two WAN links (different providers) and to provide resiliency we want to run two different STG groups (different VLAN paths) between sites and a 8600 IST pair.

We cannot get the 8600's to recongnise the spanning tree groups therefore no ports block - STP is enabled in nortelSTG mode and we have successfully tested this between two 5520's - but even using the 5520 plugging into both 8600 chassis, all ports forward, no blocking. On closer inspection we can see the Root Bridge & Designated Bridge IDs on the 8600 are different which would suggest that the 8600 pairs are not communicating in the required (or any) spanning tree groups...

Any advice, pointers would be appreciated

Thanks,

Kenny

[Michael McNamara]

Hi Kenny and welcome to the forums!

Are you routing across your WAN links or bridging? Layer2 or Layer3? If you are routing across the WAN links then you can use ECMP to help "load-balance" the traffic on the links.

In any event you will need to confirm that you have Spanning Tree enabled globally and then Spanning Tree enabled on each of the ports involved. You'll need to be very careful because Nortel's IST/SMLT technology obviously violates the Spanning Tree principles so the two technologies really don't mix very well.

Cheers!

[KennyLamb]

Hello Michael and thanks.

we have segmented the WAN into a separate L3 network and are bridging between nodes of the WAN. Spanning Tree is enabled Globally and enabled on the required ports - from the attached, we are interested in STG's 5 & 6.

We had tested with the 5520's and all was OK, when plugged into the 8600's - to go live - it didn't work, didn't think to actually test STP on the 8600's as we all know, STP works (or so I thought). Don't think I have missed anything, but as we haven't actively used STP in over 6 years, thanks to SMLT, you never know...!!!
Is there anything which needs to be considered with port loop detection, etc?

Thanks again,

Kenny

[Michael McNamara]

Hmmm... do you have a link between to two ERS 8600 switches (that's not the IST) that is participating in Spanning Tree Groups 5 & 6?