HPE 1950: Problem with Link Aggregation of VLAN Trunk Ports

[rleissner]

Hey,

we have two stacked 1950 12XG which we want to connect to two stacked 1950 24G PoE. The connections between the switch stacks have to VLAN Trunk ports and we would like to have them aggregated.

But, at the moment we configure a dynamic link aggregation group on two VLAN trunk ports, they went from up to down. If we create the lagg first and add then the VLAN trunk configuration, the port also went down. Physical they are still patched and the leds on the switch stay green, but without flashing.

All switches are running the latest firmware and the VLAN trunk configuration and the link aggregation configuration is working, as long as only the one or the other is configured.

We need the VLAN configuration, but we also want link aggregation, as without it, we only have one link between our switch stacks. Have we made a mistake in the configuration or is it a firmware bug?

[parnassus · Accepted solution]

Hi! that is a totally reasonable request...and it's possible (good you have both stack fully updated, it always help).

The way you can achieve want you want is to first start by using physical ports in their default state...AKA start clean (disconnect also the cabling between both ends or disable involved physical ports), then create the LAG (Link Aggregation Group) and configure it to use LACP (IEEE 802.3ad sometime called "Dynamic" on some Switches) and do that on both ends using the physical ports you selected (AFAIK up to 8 per peer one standalone Switch or distributed on the peer Stack), once done you can finally associate VLAN id tagging (Permitted VLANs on the logical/physical uplink) and VLAN id untagging (Native PVID) directly and only on the LAG created...clearly both LAGs need to have a matching configuration (in terms of LAG Control Protocol used and VLAN tagging).

Once done, just re-enable disabled physical ports (or reconnect disconnected cables if you leaved them enabled but disconnected). That's pretty much all you need - in the correct order - to make it working.

[rleissner]

Hi,

I basically already configured it that way, BUT, I missed one important point: I configured the VLAN trunks on the LAG member ports, missed the point, that the LAG will create a virtual port. Now, when I configure the VLAN trunks on the virtual LAG port (BAGG), it is working like a charm.

Thanks a lot parnassus!

[parnassus]

Yeah, it's a common mistake...LAG wins, its member ports are managed directly by LAG...you have to forget them.