User manual

4 POS and CPOS interface configuration

Nortel Secure Router 8000 Series

Configuration -WAN Access

4-36 Nortel Networks Inc. Issue 5.3 (

30 March 2009)

The MTU value is set too small. Because the length of a QoS queue is limited, there are

too many fragments if you set a small MTU for a relative large packet. Consequently, the

packet discards from the QoS queue. You can increase the length of the QoS queue to

solve the problem.

Troubleshooting procedure

Do as follows on the routers:

Step 1 Use the display interface pos command to check the clock configuration of the POS

interfaces. If two routers are directly connected, ensure clock mode on one end is master, and

that on the other end is slave.

Step 2 Use the display interface pos command to check the MTUs of POS interfaces. The MTUs at

both ends must be the same. If the MTU is too small, increase it.

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