Reseting CSEQ counter after phone rebooting

[adeykunov]

Most vendors reset CSEQ counter to 0 after device rebooting and, therefore, at the router side I can determine whether it was a first SIP request from the restarted device or not. But Cisco devices don't reset this counter by default. Is there a way to manually (or during provisioning)  reset CSEQ in Cisco IP phones?

[Dan Lukes]

No, as far as I know. CSEQ is not required to start at zero - it may start with any value. See RFC 3261:

8.1.1.5 CSeq

   The CSeq header field serves as a way to identify and order
   transactions.  It consists of a sequence number and a method.  The
   method MUST match that of the request.  For non-REGISTER requests
   outside of a dialog, the sequence number value is arbitrary.  The
   sequence number value MUST be expressible as a 32-bit unsigned
   integer and MUST be less than 2**31.  As long as it follows the above
   guidelines, a client may use any mechanism it would like to select
   CSeq header field values.