Panasonic NN46240-710 - Manual (Page 71)

Nortel Secure Router 8000 Series
Troubleshooting - VPN___________ 2 GRE troubleshooting
• On Router C, specify the physical interface of Router C that connects with Router B as the
tunnel source interface; specify the physical interface of Router A that connects with
Router B as the tunnel destination interface.
• Configure a static route from Router A to Router C and from Router C to Router A.
You can set up a tunnel that spans multiple routers using the preceding method.
Q: Why do packets not forward correctly even after a GRE tunnel establishes
successfully?
A: The source router and the destination router must use the routes that are forwarded by the
tunnel. Only packets with GRE encapsulation forward correctly.
You can configure a static route or a dynamic routing protocol that is required on both ends of
the tunnel.
You can use the ip route-static dest-ip-address { mask | mask-length } tunnel tunnel-number
command to configure a static route. dest-ip-address is not the IP address of the tunnel
destination interface but the destination address of the packet prior to GRE encapsulation. The
outgoing interface must be the local tunnel interface, with the next hop as the address of the
remote tunnel interface.
If you choose to configure a routing protocol, you must enable it on the tunnel interface and on
the router interface that connects with the private network. To ensure that a correct route is
chosen, do not configure the next hop of the route to the physical address of the tunnel
destination as the tunnel interface.
2.5 Diagnostic tools
2.5.1 display commands
Command Description
display this Displays the basic configuration of this tunnel. Run this
command in the tunnel interface view.
display this interface Displays information on this tunnel interface. Run this
command in the tunnel interface view.
display fib Displays information on the FIB.
display this
[Nortel-Tunnel4/0/0] display this
#
interface Tunnel4/0/0
ip address 2.2.2.2 255.255.255.0
source Ethernet3/2/0
destination 192.168.1.1
gre key 10
gre checksum
#
Issue 5.3 (30 March 2009) Nortel Networks Inc. 2-17