Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Tunnel Interface Questions


I have two remote offices that I am currently replacing P2P links in and upon review of the routers in the main and remote offices, I noticed that there are tunnel interfaces configured to route via a Loopback interface.  These older circuits are DS3 lines, and the new circuit is a fibre link that is basically metro ethernet between the sites.  My question is, what is the purpose of the tunnel interfaces?  I don't see any crypto lines to enforce encryption or anything like that, the only reason I can see for them would be for QoS reasons since our VoIP system does span the WAN links.  Any input would be appreciated. 

The first office I cut over I used a simple subinterface with Vlan tagging, since that is now the fibre circuit is supposed to work and the line came up fine.  I'm just affraid I am over looking something.  I am good with firewalls and switches, but I don't touch routers every day, so I am looking for a sanity check basically.



Everyone's tags (2)
Cisco Employee

Tunnel Interface Questions


Would it be possible to post the configuration of the two routers? It would help us in understanding what the Tunnel interfaces could have been used for.

Best regards,


Super Bronze

Tunnel Interface Questions


The    Author of this posting offers the information contained within this    posting without consideration and with the reader's understanding that    there's no implied or expressed suitability or fitness for any  purpose.   Information provided is for informational purposes only and  should not   be construed as rendering professional advice of any kind.  Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In    no event shall Author be liable for any damages whatsoever  (including,   without limitation, damages for loss of use, data or  profit) arising  out  of the use or inability to use the posting's  information even if  Author  has been advised of the possibility of such  damage.


As Peter notes, configs might help.  Some reasons for running tunnels include conveying site-to-site routing info or site-to-site multicast.

CreatePlease login to create content