GRE Tunnels floating static question

[j.vong]

Hello,

I have a site configured with two GRE tunnels to two hub sites (one as primary, another as backup).

I have static route to use the primary tunnel and a floating static with higher metric to use the secondary tunnel.

Usually, I can put "keepalive" in each tunnel interface to track the tunnel up/down so that when the primary tunnel goes down, the floating static will appear as the route and use the secondary tunnel.

Unfortunately, my IOS version does not support keepalive command.

How can I get around that?

Thanks.

[olorunloba]

You could run a routing protocol, and have your static route point to an address learnt dynamically. You could also use SAA probes (but I doubt that your IOS will support that, if it does not support tunnel keepalives).

Check

http://www.cisco.com/en/US/about/ac123/ac114/ac173/Q2-04/department_techtips.html

for information on SAA probes

[Richard Burts]

Traditionally a GRE tunnel will come up when the router has a valid route to the destination and will continue to show as up/up whether or not traffic is really flowing. In recent IOS Cisco added a function of tunnel keepalive for GRE which will actually send data through the tunnel and if data can not flow it will show the tunnel as protocol down.

I believe that this is the functionality you are describing and say that the IOS on your router does not support that functionality. There may be one other solution which is static routes with object tracking. This is also a new functionality in IOS. It allows you to configure a static route and associate a tracked object with it (the tracked object may be some address reachable through the tunnel and tracking will send a ping to that address). If the tracked object is not reachable then the static route is withdrawn. This should satisfy your requirement to have a primary static through one tunnel and a floating static through the other tunnel. (check to see if your version of IOS supports this - if it is not new enough to have tunnel keepalive it may or may not have the static route with object tracking.)

If the IOS does not have either of these features available then I am afraid that the only solution I know of that will work is to upgrade the IOS to a version that does have at least one of these features.

HTH

Rick

[j.vong]

Hi Rick,

Thanks for your detailed explanation. It is very helpful. And yes, the current router doesn't support object tracking as well.

Hi Olorunloba,

Thanks for your advice on running a routing protocol in it. I will try that to see if it works.

Thanks all!!!

[Harold Ritter]

How do you get the route to the tunnel destination address? If you get it via a dynamic routing protocol, the tunnel should go down if you loose connectivity between the tunnel endpoints.

Hope this helps,