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Vlan trunk over wifi

Looking for advice on a problem we have.


We have a building with the WAN link etc. There is a separate building which is connected via a point to point wireless link.

We have Cisco 2960 switches at either end of the wireless link. The switch is divided into 2 vlans one for telephony and one for data. with links in the main building going into a netgear switch.

In the separate building we can access the data vlan but not the voice. The ports connecting to the wireless link are trunked and if I create a vlan in the main building it replicates to the separate building and the ports are a member of the correct VLAN.

I tested with the switches connected directly together and was fine so presuming something related to the wireless link, any thoughts welcome!!


Many thanks


Hello.In the case I would


In the case I would connect 2 building with routers, I mean running /29 subnet for inter-builing routing. This won't allow you to have single L2 subnet between building, but this might be not an issue in your case.


PS: otherwise you need to enable your wireless to transfer several VLANs; not sure if your AP supports this.

Community Member

Hi Vasilii, Thanks for the

Hi Vasilii,


Thanks for the reply.


Is there another way to do it that wouldn't involve extra kit as I am not sure there is budget for any extras?

Sadly I don't believe there is an option with the wireless link as I don't believe you can get onto them to configure anything but I will investigate.


Many thanks

Community Member

Hi Vasilii, When you say

Hi Vasilii,


When you say enable wireless to transfer are there different wireless point to point links available as I don't believe there is any way to configure anything on ours?



Community Member

I will assume the following1.

I will assume the following

1. Your data VLAN is the native VLAN on the trunk ports

With that in mind you probably have an MTU issue:

In trunk ports your native VLAN (Default VLAN 1, probably your data VLAN) will not be tagged so MTU=1500,

your voice VLAN will be tagged so MTU > 1500 and your wireless equipment can't handle >1500 MTU so it drops the packets. You can confirm this by changing the native VLAN on your trunk ports to the voice VLAN and see if it works. If that's your case then either change the MTU on your wireless equipment or use 2 wireless links in non trunk ports 1 for each VLAN.

Let me know if it works.

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