VLANs and Trunking

[GobBluth]

Perhaps there is something I'm missing here. My consultant just told me to configure my switch to trunk the native vlan to the same vlan as my management vlan.

This seems like a poor practice to me. Thoughts?

 

[imagoon]

Do you mind expanding on what you mean? The native vlan would have to be the same on both sides of the trunk or it won't come up. I never place the native vlans as accessible personally. There is no good reason to see traffic in most cases anyway.

 

[GobBluth]

Situation is: I have an out-of-the-box 2960 that i'm configuring to replace an old switch. I can't just copy the running config from the old one because this is a gig switch and the other isnt. So, I'm hand jamming the config on this thing and I asked my consultant about the native vlan (which is 10 on another operational switch) and he told me to trunk it to the same vlan as my management vlan.

Confused the hell out of me is what he did!

 

[imagoon]

In that case, I wouldn't... My native vlans are normally blackholes.

 

[sactwnguy]

A trunk will come up regardless if the native vlans don't match. CDP will bitch about it and you will basically be bridging the two native vlans together but it will work, all tagged frames should pass fine. He probably means just set your native vlan on the trunk like your other switch.

 

[imagoon]

A trunk will come up regardless if the native vlans don't match. CDP will bitch about it and you will basically be bridging the two native vlans together but it will work, all tagged frames should pass fine. He probably means just set your native vlan on the trunk like your other switch.

Except that is can push other protocols like STP to push the port / vlan in to "PVID inconsistent state" which will definitely break the trunk. There is also cases where certain devices once set to 802.1Q mode simply won't accept the untagged packets and knock the link offline or generate framing errors. That is one of the main points of native VLANs.

 

[alkemyst]

In some environments a native vlan and sadly at times it has to be 1 must exist. I can't remember all those details but it involved much older tech and I think phone-based.