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GRE over IPSec tunnel issues with same subnet

I have a topology hub and spoke between 3 routers. Main router has 2 GRE tunnels. One like main link a second like backup link. Two spokes are access points from one customer and share one LAN segment for backup solution. This LAN segment is my target for SNMP purposes. So if main link fall down backup is going up. GRE tunnels I'm using with keepalive for checking state fo the link. I'm using float static route to this one segment. Backup link has worst metric.

What is a issue?

If I've applied crypto map on fysical interface everything is workig perfect. But when I use crypto map only on tunnel interfaces main link is up and IPSec SA is ok but backup link never ever reach this stage. All the time my hub router match crypto map which is designed for main link router. And then I receive message in debug cryp isa invalid proposal what is logical because my access list for main link has different public ip address like backup link. Also there are differnet ip addresses for tunnels. Has anybody experience with GRE over IPSec in this manner?

Thanks a lot



Re: GRE over IPSec tunnel issues with same subnet


It sounds like you have a config error somewhere. I have used GRE over IPSEC and have in the past a network with over 150+ tunnels. In that senario there was primary & backup tunnels, exactly what you are trying to do.

Post your configurations for review.