Native Vlan Effect on the Overall Network Performance

[jahanzaib amin]

Dear Experts,

I would like to know that did Native Vlan affect the overall Network performance and make the whole network slow and can be cause for all Network devices to be failure or disconnect. I am facing this issue for the network that after apply Vlan dot1q tag native" in global Config the user disconnect from the network and also the devices.

Kindly assist on this issue with the practical scenario and result oriented conclusion.

Thanks,

JH

[Mandlenkosi Nkiwane]

Native vlan in simple terms, it means that all the traffic that will normally be untagged [normally transmitted as vlan 1 traffic] will all be tagged as Vlan x as soon as you change the native vlan to x.

The kicker is this, if that vlan x is not on the trunks, all that traffic will be dropped on these trunks.

There may be other reasons for your issue, however in order for everyone on this forum to understand your issue, it is better to provide a simple topology picture and the configs that you are working with.

Also check out this thread:

https://supportforums.cisco.com/discussion/11700441/what-difference-between-default-vlan-and-native-vlan

Thanks,

HTH.

[Julio Carvajal]

Hello  JH,

Native Vlans should not affect perfomance or cause such an outage unless the network setup is not properly implemented.

As has been already said the native vlan is just used to send traffic without a dot1q tag, that's all.

By default is on vlan 1 but you could (and is cisco recommendation to change it).

Now using the vlan dot1q tag native you are going to start adding a dot1q header to the frames send over a trunk from this vlan.

What do you need to look for at this point on your network?

• Make sure all of the switches have the same VLAN as the native one (CDP will be in charge of telling you if this is happening or not).
• Make sure that if you enable the vlan dot1q tag command you do this on all of the switches, otherwise switches will basically not forward the traffic reveceived with a tag to that vlan as it should has been received without it.

Does it makes sense?

Please check that and get back to us.

Regards,

Jcarvaja