Recursive routing

Created Apr 01, 2017 11:28:37Latest reply Apr 01, 2017 14:32:39 568 1 0 0

This is GRE tunnel setup between two router. The public IP of router A is 1.1.1.1, public IP of router B is 2.2.2.2. Customer wants to connect two site through tunnel. All traffic from router B will first go to router A and then either access to internet or private network. Customer finds that after configuring router A and B, tunnel is down in state. Below is the configuration of router A and B.

Configuration of router A:

Int tunnel 0/0/1 
Tunnel-protocol gre
Ip address 192.168.0.1 255.255.255.252
Source 1.1.1.1
Destination 2.2.2.2

Int vlan 1
Ip address 10.1.1.1 255.255.255.0

Ip route 0.0.0.0 0.0.0.0 1.1.1.100
Ip route 10.2.2.0 255.255.255.0 tunnel 0/0/1


Configuration of router B:

Int tunnel 0/0/1 
Tunnel-protocol gre
Ip address 192.168.0.2 255.255.255.252
Source 2.2.2.2
Destination 1.1.1.1

Int vlan 1
Ip address 10.2.2.2. 255.255.255.0

Ip route 0.0.0.0 0.0.0.0 2.2.2.100
Ip route 0.0.0.0 0.0.0.0.0 tunnel 0/0/1

After checking the configuration, it was found that in router B, tunnel can’t find its destination end because it choose its own default route which results in recursive routing.
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  • x
  • convention:

Adamcolob     Created Apr 01, 2017 14:32:39 Helpful(0) Helpful(0)

Change the default route in router B to be static:

Ip route 0.0.0.0 0.0.0.0 2.2.2.100
Changes to
Ip route 1.1.1.1 255.255.255.255 2.2.2.100

Tunnel then change to up in state and the problem is solved.
  • x
  • convention:

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