I've got a problem with a Cisco 2821 router [IOS ver. 12.4(24)T4] which doesn't forward dhcp request over a GRE tunnel; both of interfaces (GRE and LAN) belong to the same VRF context. I hereby attach a piece of configuration:
ip vrf guests rd 10:3 ! interface Loopback0 ip address 172.22.109.1 255.255.255.255 ! interface Tunnel10 ip vrf forwarding guests ip address 10.200.128.9 255.255.255.252 no ip route-cache cef no ip route-cache tunnel source Loopback0 tunnel destination 172.25.121.6 tunnel key 0 tunnel checksum ! interface GigabitEthernet0/0.474 encapsulation dot1Q 474 ip vrf forwarding guests ip address 10.200.61.1 255.255.255.0 ip helper-address 172.25.68.26 ! ip forward-protocol nd ip route 0.0.0.0 0.0.0.0 172.22.105.33 ip route vrf guests 0.0.0.0 0.0.0.0 Tunnel10
The tunnel works fine for all except for the DHCP requests. This is the output for "debug ip dhcp server packet", "debug ip dhcp server events" and "debug ip packet 199" where 199 is an ACL for bootpc/bootps packet matching
Thank you for letting us know! Hmm, I suppose the CEF had some kind of inconsistency in its contents, causing your packets to be mis-forwarded. I've seen similar problems before. I would also hypothesize that if you restarted your router and put back the commands you've removed, it would still work.
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