Nortel Networks 8000 - Manual (Page 96)

Nortel Secure Router 8000 Series
Configuration -WAN Access 4 POS and CPOS interface configuration
Step 2 Check the clock configurations of the interfaces by using the display interface pos command.
If two routers are directly connected, ensure clock mode on one end is master, and that on the
other end is slave.
—End
4.8.2 Line protocol status of POS interfaces is Down
Fault description
After configuring the POS interface of the routers, use the display interface pos command to
view the interface status and find that the status of physical layer is Up, but the link layer is
Down.
Fault analysis
The possible causes are:
• Physical parameters, such as POS port clock and scramble, do not match with those of
the remote end.
• Configuration of link layer protocol does not match with the remote.
• After loopback mode is configured, the link protocol is Down.
• CRCs on both ends are not consistent, which leads to the Down state of the link protocol.
Troubleshooting procedure
Do as follows on the routers:
Step 1 Use the display interface pos commands to check the interface configurations.
Step 2 Compare whether link layer protocol, scramble, clock configuration, and CRC of interfaces
on both ends are consistent according to the commands output. If not, modify them to be
consistent. If two routers are directly connected, ensure clock mode on one end is master, and
that on the other end is slave.
Step 3 Disable loopback mode if you have configured it on the interfaces.
—End
After the previous configuration, the link protocol must be in the Up state.
4.8.3 Severe packet loss on a POS interface
Fault description
IP packets on POS interface are lost severely.
Fault analysis
The possible causes are:
• The POS clock is configured incorrectly (resulting in plenty of CRC errors).
• The MTU configurations on both the ends are not matched.
Issue 5.3 (30 March 2009) Nortel Networks Inc. 4-35