GRE packet matching and routing

[01Boxer]

Hi,

I'm trying to confirm some details on GRE tunnelling, I hope someone knows the answer to, or can point me in the right direction, please?

Firstly, is traffic still encapsulated and GRE packets routed according to the underlying network routing, even if the destination router of the tunnel is unavailable (failed)?

Secondly, when the source router has a route-map (referencing an ACL) to match traffic, will matching traffic always be encapsulated and sent onto the network?

I know these are sort of similar questions, I'm trying to understand possible failure scenarios from source to destination.

Thanks in advance!

:)

[dangleminh · Accepted solution]

Firstly, is traffic still encapsulated and GRE packets routed according to the underlying network routing, even if the destination router of the tunnel is unavailable (failed)?

=>If the GRE tunnels destination is down, the route will be withdrawn, service impact. The underlying network does not know about routing.

Secondly, when the source router has a route-map (referencing an ACL) to match traffic, will matching traffic always be encapsulated and sent onto the network?

=>All traffics will be encapsulated as long as they are routed via GRE tunnel.

[01Boxer]

Hi, thanks for the reply! So just to confirm, of the remote tunnel end point is down, will traffic matching the route-map be passed over the network un encapsulated?

[dangleminh]

If the underlying network knows how to route the traffics, the packets will not be encapsulated.

If the underlying network has no routing information, the packets will be dropped.

[01Boxer]

Thank you very much!