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1920S with two vlans and trunk doesnt work

New Member

1920S with two vlans and trunk doesnt work


we have Problems with two HP Switches:


HPE OfficeConnect Switch 1920S 48G 4SFP JL382A

1x HPE OfficeConnect Switch 1820 24G J9980A

These both are connectet with 2 LWL cables. I have all 4 Ports configured with 2 VLANs (1+2) and all 4 Ports in mode tagging and include. So it works with 1 LWL Connection fine! Now i will make a trunk over the 2 LWL connections. When i configured these, the hole network breaks! All connections are lost on all PC´s..... and the configurend Ports are automatic in mode tagged and exclude on both vlans ?!

I need Help

Honored Contributor

Re: 1920S with two vlans and trunk doesnt work

Hi! I don't know what LWL means but, anyhow, the wrong part here is that you didn't create a LAG (Link Aggregation Group = a logical interface which is made of the aggregation of two or more physical interfaces) first...but you simply connected both Switches with two cables de-facto causing a Loop (STP stepped in probably to stop the caused broadcast storm, hopefully...if (R)STP or (M)STP was enabled).

So disconnect involved ports and delete related configurations to bring them to their default configuration status (pair on Switch 1 and pair on Switch 2). Create a LAG (with LACP as control protocol) on Switch 1 and on Switch 2 by using respectively ports of pair 1 and ports of pair 2. Apply VLAN tagging on the LAG only and only as last step. Reconnect cables.

Check STP priority so one Switch should have priority 0 (highest) to act as STP root and the other can be left with a lower value (strictly higher than 0).



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