GRE Tunnel through intermediate routers

[hxmengmetro]

Hi All,

We have a Hub-Spoke network. The Hub is connected to remote sites through our own fiber or ISP VPN. Some sites connected to one intermediate router and then connect to core router in the hub. At this time, all the routing is static. Some time, when the intermediate router has issue, the remote site can't see the connection is down if the directly connected interface is still up while the other interface connected to the hub is down. Sure, you can ping and your end user in the remote site will notice the connection is down but I would like have the router capable of knowing the connection is down. So I think GRE could be good fit here.

As I understand, as long as the two end's tunnel interfaces are routable, it doesn't matter that we have one or two intermediate routers between the hub and remote sites. Am I correct?

Thanks for the help. Really appreciated.

Lou

[cadet alain]

Hi,

but I would like have the router capable of knowing the connection is down

Then you can use ip sla:  http://www.cisco.com/en/US/docs/ios/12_4/ip_sla/configuration/guide/hsla_c.html

Regards.

Alain.

[hxmengmetro]

Thanks Alain. This is really another good way to go. It seems service providers use this very often. This is new to me but I will look into that. In addition, how about GRE? Is this capable doing what I want to do? Thanks.

Lou

[francisco_1]

Lou,

Your problem is with static routing there is no keep alive mechanism to detect when there failure within your cloud. The common solution to your problem is to run dynamips routing protocol such as OSPF. As for GRE you will need to have keepalive turn on for GRE to even detect the other side is down.

The common solution to your problem is you can run OSPF over GRE and enable GRE keepalive on the GRE tunnel interface and have the OSPF timers higher than the GRE keepalive timer so if there is a failure somewhere within your cloud, the GRE interface flap down will cause OSPF to detect it as well.

Francisco.