SIP Phone Not Registering

[gilbertnb]

I have several SIP phones that I am trying to connect to our local Cisco CME call manager.  The phones that are directly connected to the switch that the CME is connect to work fine and register.  The phones that are coming in through our Sophos XG firewall are not sending the authentication header after they receive the initial 401 response from the CME.  The 401 response from the CME includes the WWW-Authentication response telling the phone how to respond but the phone just sends the same SIP registration request without the authentication information over and over.  We have compared the traffic between the phone that registers with the phone that does not register and it appears that the phone just won't send the authentication information.  Where should we be trouble shooting?  Do we look at the initial TFTP traffic from the server to validate that the config info is getting to the phone initially so it can be sent back to the CME or should we be looking at the configuration of the CME to determine if there is some sort of disconnect with configuration of the phone.  Also, when we results from "show voice register statistics" there are over a thousand registration requests, but only the ones on the local network are recorded under a specific pool count.  All the phones that are not being registered are only recorded in the Global statistics.  We have opened a ticket with Cisco and Sophos with no luck from either.

[Dan Lukes]

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The phones that are directly connected to the switch that the CME is connect to work fine and register.  The phones that are coming in through our Sophos XG firewall are not sending the authentication header after they receive the initial 401 response from the CME.  The 401 response from the CME includes the WWW-Authentication response telling the phone how to respond but the phone just sends the same SIP registration request without the authentication information over and over.  We have compared the traffic between the phone that registers with the phone that does not register and it appears that the phone just won't send the authentication information. 

You didn't disclosed captured packets, so we can neither confirm nor dispute your conclusions.

May be phone's syslog&debug messages may help. Unfortunately I'm not familiar with Phone<->CME interaction (we are using standard SIP call control proxy) so I can't advise how to turn them out and capture in your particular case.