NOTE: All the devices are pre-configured with Frame-relay / DLCI.
Configuration.
SW1:
Int tunnel 1
Tunnel source 155.1.37.7
Tunnel destination 155.1.0.5
Ip add 155.1.75.7 255.255.255.0
Tunnel mode gre ip
R5:
Tunnel 5
Tunnel mode gre ip – default (not shown in the running config)
Tunnel source 155.1.0.5
Tun dest 155.1.37.7
Ip add 155.1.75.5 255.255.255.0
Show ip route
SW1:
show ip route
R3: shutdown the int s1/0 to see the changes on the routing table from R5.
R5:
Show ip route
Debug ip routing – to see the ip routing process, you will see that there is a recursive routing and it will disable the tunnel interface. – IT’S HAPPENING IF YOU HAVE MULTIPLE INTERFACE OR LOAD SHARING INTERFACE TO REACH THE DESTINATION TUNNEL.
To fix this on R5 side and SW1
R5:
Access-list 20 deny 155.1.37.0 – to block the route being learned and fix the recursive routing due to down interface on R3.
Access-list 20 permit any
Router rip
Distribute-list 20 in tunnel5
Show ip route 155.1.37.0
SW1:
Config t
Ip route 155.1.0.0 255.255.255.0 155.1.37.3
Show ip route