Routing Packets To A Gre Tunnel; Preventing Loops In Gre Tunnels; Optional Gre Tunnel Features - Avaya G350 Administration

For a list of optional GRE tunnel features, refer to
additional GRE tunnel CLI commands, refer to

Routing packets to a GRE tunnel

Packets 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
table on page 136.
•
The packet is routed to the tunnel interface dynamically by the router protocol.
•
The packet is routed to the tunnel interface via policy-based routing. See
based routing

Preventing loops in GRE tunnels

It is strongly recommended that you assign a high route preference to the destination address of each
GRE tunnel. This is to reduce the possibility of nested tunneling. Nested tunneling takes place when a
router tries to send a packet to the tunnel by way of the tunnel interface, thereby creating a loop. If a loop
occurs, the G350 displays a message that the tunnel is down because of nested tunneling.
To assign a high route preference to the destination address of a GRE tunnel, use the
in the following syntax:
ip route [destination] [next hop] high
where destination
a local router.

Optional GRE tunnel features

You can configure the following optional features in GRE tunnels:
•
Tunnel keepalive
•
Dynamic MTU discovery
on the current route through the tunnel.
Tunnel keepalive
The tunnel keepalive feature sends keepalive packets through the tunnel interface to determine whether
the tunnel is up or down. This feature enables the tunnel's source interface to inform the host if the tunnel
is down. When the tunnel keepalive feature is not active, if the tunnel is down, the tunnel's source
interface continues to attempt to send packets over the tunnel without informing the host that the packets
are failing to reach their destination.
Use the
tunnel keepalive
keepalive feature. Use the
Administration of the Avaya G350 Media Gateway
June 2004
on page 177.
is the IP address of the tunnel destination interface, and
— enables periodic checking to determine if the tunnel is up or down.
— enables periodic checking to determine and update the lowest MTU
command in the context of the GRE tunnel interface to enable the tunnel
form of this command to deactivate the feature.
no
Optional GRE tunnel features
Additional GRE tunnel parameters
Configuring the router
Configuring GRE tunneling
on page 141. For a list of
on page 142.
Configuring the routing
Configuring policy-
command
ip route
next hop is the IP address of
141