Nortel Networks NN46110-602 - Manual (Page 81)

Chapter 4 Troubleshooting 81
Nortel VPN Router Troubleshooting
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:
1 Check 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.
2 Examine the Manager Statistics event log with debugging enabled. Any
WAN-related log messages probably indicate some sort of error.
3 Report 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:
1 Check 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.
2 If the connection fails during authentication, then try disabling the PPP
Authentication settings. A problem during Network Negotiating is usually
due to misconfigured IPCP options.
3 Verify that all the authentication settings match the ISP-recommended router
configuration.