Cisco IP Telephony Troubleshooting Guide for Cisco CallManager Release 3.0(1)
© 2000 Cisco Systems, Inc. 28
4. Look for these and any errors that may have occurred around the time that the phone(s) reset.
5. Start an SDI trace and try to isolate the problem by identifying any common characteristics in
the phones that are resetting. For example, check whether they are all located on the same
subnet, same VLAN, and so on. Look at the trace and determine:
• If the resets occur during a call or happen intermittently
• If there any similarities of phone model – Cisco IP Phone 7960, Cisco IP Phone 30VIP,
etc.
6. Start a Sniffer trace on a phone that frequently resets. After it has reset, look at the trace to
determine if there are any TCP retries occurring. If so, this indicates a network problem. The
trace may show some consistencies in the resets, such as the phone resetting every seven
days. This might indicate DHCP lease expiration every seven days (this value is user-
configurable; could be every two minutes, etc.).
Dropped Calls
Dropped calls occur when a call is prematurely terminated. You can use CDRs to determine the
possible cause of dropped calls, particularly if the problem is intermittent. Dropped calls can be
the result of a phone or gateway resetting (see above section) or a circuit problem, such as
incorrect PRI configuration or error.
The first step is to determine if this problem is isolated to one phone or a group of phones.
Perhaps the affected phones are all on a particular subnet or location. The next step is to check
the Event Viewer for phone or gateway resets.