Hi List,
FYI.
We have been using CentOS 6.4 and have 2 vpn/gre tunnels to separate cisco rtrs using ospf. with kernel 2.6.32-358.23.2
We have upgraded to 6.5 bit using kernel 2.6.32-431.5.1 and the exact same configuration scripts for our vpn/gre tunnels.
What I see is the first gre tunnel works great and I get an ospf neighbor.
The second tunnel comes up and I can ping across it and I see our side sending hello packets in the gre tunnel but I never receive any hello packets from the cisco.
The cisco sees our hellos because it goes into the Init state. I do a tcpdump and I see esp traffic coming from the cisco like it is sending hellos but they never show up in a tcpdump on the gre tunnel. It is like the kernel is not delivering them.
Also my gre tunnels on CentOS 6.5 are named gre1@NONE and gre2@NONE with an ip a s, while on the 6.4 CentOS system they show up as only gre1 and gre2? Whats with the @NONE?
Looking at the Changelog of the kernel a lot of changes to the ip_gre module were made in 2.6.32-380