Panasonic NN46240-710 - Manual (Page 70)

2 GRE troubleshooting
Nortel Secure Router 8000 Series
_________ Troubleshooting - VPN
Q: Why is the tunnel source interface found to be another interface when the
display this interface command is run in the interface view? This happens when
specifying an IP address as the tunnel source address, and this IP address belongs
to some source interface.
A: The reason is that after tunnel configuration, the IP address assigned for the tunnel source is
transferred to another interface.
After the tunnel detects that the source interface where its source address is located has changed,
it updates the source interface of the tunnel source.
Q: Why is the status of the tunnel still down after the IP address, source address,
and destination address are specified for the tunnel?
A: To change the tunnel status to up, the following conditions must be met:
• An IP address is assigned for the tunnel interface.
• The source and destination addresses are specified.
• Reachable routes exist between the source and destination addresses.
If the status of the tunnel is down even after you meet all three conditions, check for reachable
routes between the source and destination addresses. If no reachable routes exist, use the ip
route-static command to configure a static route or run a dynamic routing protocol to allow
reachable routes between the source and destination addresses of the tunnel.
Q: Why can I not ping the IP address of the remote tunnel interface? All the
configurations are complete, a reachable route exists between the source and
destination addresses, and the tunnel is up.
A: The possible causes are as follows:
• The IP addresses of the tunnel interfaces on two ends are not in the same network segment.
• The GRE keys on the two ends are inconsistent. If only one end is configured with the
GRE key or the key-numbers of two ends are different, the fault occurs.
Q: Why does the ping fail even after I configure a multilayer embedding tunnel?
A: A tunnel supports up to three-layer embedding. If this specification is exceeded, the ping will
fail. Check the tunnel layers.
Q: Suppose three routers exist: Router A, Router B, and Router C. Router A and
Router B directly connect; Router B and Router C directly connect; I need a tunnel
between Router A and Router C. In this case, what configurations should be
performed to establish the tunnel successfully?
A: You need to perform the following configurations:
• First, complete the interface configuration on Router A, Router B, and Router C, and
create a tunnel interface on both Router A and Router C.
• On Router A, specify the physical interface of Router A that connects with Router B as the
tunnel source interface and specify the physical interface of Router C that connects with
Router B as the tunnel destination address.
2-16 Nortel Networks Inc. Issue 5.3 (30 March2009)