Administration of the Avaya G350 Media Gateway - Avaya Support

Configuring the routerRouting packets to a GRE tunnelPackets can be routed to a GRE tunnel in the following ways:●●●The tunnel interface is configured as the next hop in a static route. See Configuring therouting table on page 163.The packet is routed to the tunnel interface dynamically by a routing protocol (RIP orOSPF).The packet is routed to the tunnel interface via policy-based routing. See Configuringpolicy-based routing on page 273.Preventing nested tunneling in GRE tunnelsNested tunneling occurs when the tunnel’s next hop for its destination is another tunnel, or thetunnel itself. When the next hop is the tunnel itself, a tunnel loop occurs. This is also known asrecursive routing.When the G350 recognizes nested tunneling, it brings down the tunnel interface and produces amessage that the interface is temporarily disabled due to nested tunneling. The tunnel remainsdown until the tunnel is reconfigured to eliminate the nested tunneling.In addition to checking for nested tunneling, the G350 prevents loops in connection with GREtunnels by preventing the same packet from being encapsulated more than once in the G350.Several things can lead to nested tunneling in a GRE tunnel:● A static route exists on the source tunnel endpoint that tells the tunnel to route packetsaddressed to the receiving tunnel endpoint via the tunnel itself.●The local endpoint of the tunnel learns the tunnel as a route to the tunnel’s remoteendpoint via OSPF or RIP.168 Administration of the Avaya G350 Media Gateway