Duplicate Static Routing For Failover Over GRE - Can You Help?
I think i am going mad, i should know the answer to this but i have thought about it that much that not even the simplest things are making sense to me now, so im hopingyour wise brains can help me out.
I have a situation where i need to route the same IP block, a /29 via a static route to another router that is on our network, this router has a weird config where its connected to the network via two /30 GRE tunnels that are encrypted, they are two GRE tunnels that work over two WAN gateways for redundancy. If one gateway does down then there is still a second GRE tunel up to route the /29 over.
To do this would i need to have 2* static routes pointing the /29 at both ends of the /30 GRE tunnel, so if one went down it could still route the /29 over the second tunnel. Or would having two static routes pointing a single /29 network to two different /30 destignations on the same router cause issues?
The /29 is so i can have public IP addresses on a router interface, then have 2 X default routes pointing to both ends of the /30 GRE tunnels, thats the plan anyways.
Is there a way to make to make this work? will it work?
Many thanks for your reply, i forgot to mention that the router with the default routes (customer cpe) is a non cisco, its a Mikrotik but our entire core network is Cisco. I need to put the static routes on our edge cisco device to route the IP block 22.214.171.124 /29 for example to the Mikrotik. In your example i think you explained about routing the traffic back using default routes, what about routing the /29 from our core to the customer router over the GRE tunnels?
The two GRE tunnel addresses are 126.96.36.199 /30 and 188.8.131.52/30
So could i have two static routes as follows on my cisco edge router,
ip route 184.108.40.206 255.255.255.248 220.127.116.11 200
ip route 18.104.22.168 255.255.255.248 22.214.171.124 200
Im sorry my knowledge of a floating static route is not as good as it should be, if i set the AD of 200 on both the statics like above, would that load balance traffic over both routes? what would happen if 126.96.36.199 went down, would 50% of the traffic be blackholed, if indeed it was blackholed?
If you could clear that up for me i would really appreciate it.
Be aware of the tunnel behavior, that is, if the tunnel destination is in the routingtable, then the router consider the tunnel is up, regardless if there is something in the transit that is broken. If this happens half of the traffic will be blackholed.
To overcome this, You can configure tunnel keep-alive. Or You can use a routingprotocol over the tunnels, then the protocol will take care of broken tunnels.
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