Showing results for 
Search instead for 
Did you mean: 

VoIP over L2TPv3, is it possible going from router to router?


I've got to extend our voice VLAN over a WAN backbone. One of the old documents (2013) says L2TP does not support CDP ,LLDP, STP, or VLAN trunking, unless you use a L3 switch.   


My current design is:  

A1 switch with VoIP access ports

A1 router

backbone network

A2 router

A2 switch



Is it possible to have a L2TPv3 tunnel between A1 to A2 routers, and push the VoIP traffic from the A1 switch to the A2 phone?  I am failing so that because of the lack of CDP?



5 Replies 5

VIP Community Legend VIP Community Legend
VIP Community Legend

Hope the below example works for you : ( check the router requirement, you mentioned router, we guess all cisco devices here)


***** Rate All Helpful Responses *****

How to Ask The Cisco Community for Help

Hyperlink is broken, sorry.   Do you know if VoIP can be carried over a L2TP tunnel?  Thanks.

VIP Mentor VIP Mentor
VIP Mentor

Marce1000.  Per the link you sent me, it states:   

  • Support for L2 protocol tunneling (Cisco Discovery Protocol, Spanning Tree Protocol, VLAN Trunking Protocol, and Link Layer Discovery Protocol) requires that the device is a switch. This switch needs to be L3 aware in order to be able to tunnel traffic and limit the possible choices.

Does tha mean I cannot run VoIP over a tunnel using routers?  Do they need CDP/LLDP ?


Giuseppe Larosa
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Hello @jimmycher ,

I would suggest you to create a VOIP subnet on A2 site instead of attempting to extend the existing Voice VLAN over WAN.


CDP and LLDP are spoken between the IP phone and the connected switch port to allow the IP phone to identify itself and to get Voice Vlan info.

On A2 switch you need to define the voice VLAN on user ports in the same way you do on A1 switch.

The L2 transport service should be limited to VOIP packets and signaling.


Hope to help



Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Recognize Your Peers