native vlan mismatch

Unanswered Question
Oct 25th, 2009

hi Experts,

I have some queries about native vlan mismatch

1. If i am not wrong , swich bpdu , cdp , PAgp and dtp are carried over native vlan , if native vlan from both switch is different then how it works.

2. if we prune native vlan from trunk by removeing native vlan from trunk allowded vlan list then how still will be swich sent and received native vlan .(reference to bcmsn certification guide)

Thanks in advance.

I have this problem too.
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Muhammad Zeesha... Sun, 10/25/2009 - 20:46

These Protocols use Vlan 1. And Vlan 1 cannot be pruned or disabled.

Even if you Prune Vlan 1 still they will use Vlan 1.

Try to Lab it up and see the results

Zeeshan

Jerry Ye Sun, 10/25/2009 - 21:59

Just some additional info on top of Zeeshan's. The below doc is the best practice for CatOS but the control plane protocol is the same for IOS. Please see the summary section under VLAN 1 for more info.

http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a0080094713.shtml#cat_control

For your 2nd question, native vlan is really means when the switch is receiving untagged user traffic, it will use the native VLAN to forward it.

HTH,

jerry

Amit Singh Sun, 10/25/2009 - 21:43

Agreed with Zeeshan on this. It uses Vlan 1 to send and receive control traffic.

Removing vlan 1 from the trunk is called as Vlan 1 minimization. With this feature enabled, no user traffic is sent or received on the trunk. The switch CPU continues to send and receive control protocol frames.

regards,

-amit sing

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