HP 2920 stacking redundant connection not working

[CraigZ]

Hi,

I have set up 2 HP 2920 Stacks in our workplace. One Core Stack which does our routing  (consists of 3 switches) and another called Prod Stack which is in another building and  connected to the Core Stack by 2 fibre links utilising the 10GbE modules and transceivers.

We have MSTP enabled on all switches and the CoreStack is the root bridge. The ports that connect the 2 stacks are in the following states

CoreStack                                                                   Prod Stack

1/A2 - Forwarding <--------------------------> 2/A1 - Disabled

2/A2 - Forwarding <--------------------------> 1/A1 - Forwarding

Shouldn't port 2/A1 in the Prod Stack be in a blocking state.

When we fail over the active line the redundant line doesn't start forwarding packets

Both stacks are on firmware WB.15.18.0006.

Any help greatly appreciated.

[EricAtHP]

Since both ends are stacks, one logical switch on each end, why don't you setup an LACP link aggregation so that you get redundancy and more bandwidth?

On each end, use the 'trunk' command and specify the ports.

You can leave spanning tree enabled but it will see it as a single link so it will be forwarding at both ends. Spanning tree will end up just being a saftey in case something gets connected incorrectly.

[CraigZ]

Hi,

That is possible but the redundant line won't enough come up. There is no traffic going across it when we fail over, so a trk wouldn't be working probably anyway

[EricAtHP]

Make sure they are the same type on both ends. For example, the command should look something like this:

trunk 1/a1, 2/a1 trk1 lacp

LACP negotiates the link. So if one end is configured for LACP but the other end isn't, both links won't come up.

[Michael Patmon]

Hello.  So one side is showing link and one side is not?  Can you "show interface brief" on both side for those 4 ports?  Also "show lldp info remote" for those 4 ports as well.

[CraigZ · Accepted solution]

Hi,

Yes I ran those commands and the other switch didn't show and the port is enabled.

I tested the line with 1GbE transceivers and it worked.

I know believe that the issue arose from the fibre cable being OM2 between the buildings which only gives 80 meteres distance for 10GbE. It is strange as 1 line works with 10GbE transceivers and the others don't.

Anyway thanks for all your input and help.