Alcatel Unleashed

Hello members,

running here following mc-lag environment:

|-------------Firewall------------|----------Sync-----------|---------------Firewall------------|
|                                                                                               |
||- ---------|server 2|---------||                          ||-------------|server 4|----------||
||                              ||                          ||                                 ||
||    |------|server 1|------|  ||                          ||    |--------|server3|-------|   ||
||    |                      |  ||                          ||    |                        |   ||
|6900-1|-----VF-Link------|6900-2|--------------------------|6900-3|------VF-Link--------|6900-4|
|                                                                                               |
|----------------------------------------------------------------------- -----------------------|

First it was one stp ring over all 6900 machines. Then MC-LAG was configured. But theres somewhere a loop.
If the link between (6900-2 and 6900-3) or (6900-1 and 6900-4) is set to admin down the loop disappears.

On which ports Spanning Tree must not be enabled to accomplish that the redundant link can be used again?
Or maybe there could be some other reason that there's a loop?

Thanks in advance,
Tobias Hachmer

I don't think that setup is supported (see the Network Guide). STP is disabeld on VFLs and all MC-LACPs. Not sure whether Loopdetection should have disabled the link (but still then it's not a backup.

What should work is when you do away all the MC-LAG Stuff and instead create a Virtual Chassis out of 6900-1 and 2 and second one out off 6900-3&4 (similar to the Stacks in 6850 or 64XX). There STP is working as usual and the redundant link should be STP blocked as usual.
Unfortunatley the requires some reconfigurations and is nothing i would to i a production network (so have a maintance Window, prepare configs and a rollback scenario)

I only had a scenario with multiple VCs in Lab (ALU Datacenter Course), but it worked fine there. My VCs in production only consist of two "Core" Devices e.g. two OS10k or two 6900

you can try to LACP both links: (6900-2 to 6900-3) and (6900-1 to 6900-4) and disable stp

do you have 6900-1/6900-2 in a different MC-LAG domain than 6900-3/6900-4?

you show then be able to do MC-LAG. look in the docs for the command:

multi-chassis chassis-group <#>

The topology is not supported. Please use LACP between the MC-LAGs/VCs as already suggested.

B