Nortel Networks NN46110-602 manual Check the Hdlc framing, Check the PPP layer

Chapter 4 Troubleshooting 81

Check the HDLC framing

Assuming that the T1/V.35 interface is operating correctly, use the following steps to determine whether the HDLC layer is up and running properly, and to provide information for Nortel Customer Support for further diagnosis:

1Check that there are no input or output errors reported on the Manager WAN statistics window. Also look to see if the input and output counters are incrementing at all. If the input/output counters are not incrementing, or are incrementing by huge amounts, then there are probably framing or timing errors on the link. Also, a large percentage of input errors can indicate a problem with the FCS (Frame Check Sequence) calculation.

2Examine the Manager Statistics event log with debugging enabled. Any WAN-related log messages probably indicate some sort of error.

3Report any of the preceding errors and messages to Nortel Customer Support for assistance in diagnosing the HDLC framing problem.

Check the PPP layer

If the WAN link is passing frames back and forth, but IP packets are not flowing, then the problem can be how PPP is configured.

To examine the state of the PPP connection, and to provide information for Nortel Customer Support for further diagnosis:

1Check whether the state of the PPP connection is changing at all by periodically clicking Refresh while viewing the WAN statistics window. If the state is always Down, PPP may not know that the link is up. If the state toggles between Dead and LCP Negotiating, PPP is trying to come up but cannot. This is probably due to a problem with the underlying layers, although it can also be a bad configuration of the LCP options.

2If the connection fails during authentication, then try disabling the PPP Authentication settings. A problem during Network Negotiating is usually due to misconfigured IPCP options.

3Verify that all the authentication settings match the ISP-recommended router configuration.

Nortel VPN Router Troubleshooting