TMS zl Management and Configuration Guide ST.1.2.100916

7-196
Virtual Private Networks
Configure a GRE Tunnel
In the example figure, the forwarding interface would be the Gateway VLAN,
and the gateway for the route would be a router in this VLAN.
Caution Dynamic routing can introduce an issue. The remote tunnel gateway might
advertise a route to the tunnel destination address through the tunnel itself.
If this is the best, most specific route to the destination, then the module will
add it to its routing table. This causes causing recursive routing, which shuts
the tunnel down. Therefore, if you plan to use dynamic routing on the tunnel,
it is best practice to add a specific static route to the tunnel destination address
through the proper gateway. (Make sure to give this route an administrative
distance lower than the routing protocol.)
Figure 7-160. Example GRE Tunnel
Configure Routes that Use the GRE Tunnel Interface
In order for the TMS zl Module to send traffic over the GRE tunnel, it must
have routes to the appropriate subnets that use the GRE tunnel interface. You
can:
■ Create static routes
See “Configure Static Routes” on page 7-197
■ Set up RIP on the GRE tunnel interface
See “Configure RIP on a GRE Tunnel Interface” on page 7-199.
■ Set up OSPF on the GRE tunnel interface
See “Configure OSPF on a GRE Tunnel Interface” on page 7-201.