Switchport trunk native Vlan command

Unanswered Question
Apr 7th, 2008

Hello all...

Quick question. I have a Cisco 2950T switch that I have connected to an HP 1800 24 port switch. The link is configured as a trunk port that carries 2 Vlans. The question is when the Cisco switch is configured with the switchport trunk native vlan command it will not talk to the HP but when I remove it everything works. This command works when there are 2 Cisco switches together. Can someone explain this command and what it does?

Thanks,

Matt

I have this problem too.
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jjeffrey Mon, 04/07/2008 - 11:03

We had the same issue. This come from the way VLAN tagging in done. Cisco tagges all VLANs and HP does not tag the Native VLAN. We could not use the switch we demo due this issue. HP did not have a working at the time.

jgreenwoodii Mon, 04/07/2008 - 17:52

Not sure on the HP 1800 model but when you are using a dot1q trunk on a cisco switch, by default the native vlan will be vlan 1. Now you can change the native vlan from 1 to another vlan #. You need to make sure the end device your connecting supports a native vlan other than 1. If your using another switch you should be fine as long as the native vlan matches on the other end.

srue Mon, 04/07/2008 - 18:20

when you add a vlan to a trunked port in an HP switch, you have to explicitly state whether it's tagged or untagged - thus defining the native vlan.

(be careful, in HP terminology a trunk is what Cisco refers to as etherchannel technology).

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