I am attempting to set up multiple GRE tunnels from a host to nine remote sites. The host has an Adtran 904E router and the remotes have Cisco 891 and 887s
I am using 192.168.10.1 255.255.255.0 and 192.168.10.2 255.255.255.0 for the inside tunnel addresses. When I go to set up the second tunnel on the same interface using 192.168.10.3 255.255.255.0 and 192.168.10.4 255.255.255 0, I get a subnet error.
How should these tunnels be addressed?
Many thanks in advance.
Try putting each each tunnel in a separate subnet
tunnel-1 192.168.10.1 255.255.255.0 and 10.2
tunnel-2 192.168.11.1 255.255.255.0 and 11.2
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"Regular" GRE tunnels are usually configured at p2p, i.e. with a /30 or /31. They can be configured with larger IP blocks, wasting IP space, but that will work fine as long as the address spaces don't overlay.
If you want multiple sites to share the same subnet, they you'll want to implement MGRE. Then you can use the IP addressing as you intended.