I have a problem setting up GRE tunnel ( w/o any encryption) between Cisco 2611 and 2621. IOS version is the same c2600-ik9o3s3-mz.123-26.bin.
The problem is that after configuring both devices I can not ping 2611 from 2621 over tunnel. I added a rule on 2611 WAN interface, so I could see incoming GRE packets. During the ping process I do NOT see any matches on this rule. But as soon as I ping 2621 from 2611, 2621 can ping 2611 as well and I see matches on this rule.
The same thing happens with IPSEC tunnel, but first I would like to resolve issue with GRE as I think the have the same roots.
Can you please advice how I can resolve this issue ?