Protocols and Endpoints

A new batch of SIP endpoints is deployed to a CUCM cluster. The phones obtain DHCP addresses, download their configuration from TFTP, and NTP is synchronized. However, during registration the phones cycle through 'Registering' and never fully register. A packet capture shows the phone sends a SIP REGISTER, and CUCM replies with a '401 Unauthorized' challenge, but the phone never sends a follow-up REGISTER with credentials. The phone's Digest Credentials field on the End User page is blank, and the phone's SIP Profile has 'Enable Digest Authentication' behavior enforced via the associated SIP Security Profile. What is the most likely cause?

A new Cisco IP Phone 8865 configured for SIP is failing to register with CUCM. Packet captures show the phone sends a REGISTER, CUCM responds with a 401 Unauthorized containing a WWW-Authenticate header, and the phone resends the REGISTER with an Authorization header. CUCM then replies with another 401 and the cycle repeats indefinitely. Other phones on the same subnet using the same device pool register successfully. What is the most likely cause?

A newly deployed Cisco IP Phone 8865 is configured for SIP and set to use DNS to locate its call-processing servers. The phone completes DHCP, obtains an IP address, and downloads its configuration file from TFTP, but it fails to register. Packet captures show the phone sending SIP REGISTER messages to an IP address that does not match any CUCM node, and the registrations time out. The CUCM group and device pool are correctly configured on the cluster. What is the most likely cause of the registration failure?

A new Cisco IP phone running SIP firmware is deployed at a branch site. The network supports both IPv4 and IPv6, but CUCM is configured for IPv4-only communication on its cluster-wide addressing settings. The phone obtains both an IPv4 and IPv6 address via DHCP and DHCPv6. The phone's Common Device Configuration is set to an IP Addressing Mode of 'IPv6 Only'. The phone fails to register with CUCM, and packet captures show the phone attempting to reach the TFTP and CUCM servers over IPv6 addresses that never respond. What is the MOST likely cause of the registration failure?

A network engineer registers a new Cisco 8865 SIP phone to CUCM. The phone obtains an IP address, downloads its configuration file from TFTP, and displays 'Registering.' However, it never completes registration. Packet captures show the phone sending SIP REGISTER messages on TCP port 5061, but CUCM never responds. The phone was configured with the default device security profile 'Cisco 8865 - Standard SIP Non-Secure Profile.' What is the most likely cause?

A newly deployed Cisco IP Phone 8865 running SIP firmware fails to register with CUCM. Packet captures show the phone downloads its configuration file via TFTP successfully, but it never sends a SIP REGISTER message to the primary CUCM node listed in the config. The phone displays 'Registering' and then reverts to the same node repeatedly. The device is defined in CUCM and associated with the correct device pool. What is the MOST likely cause?

A newly deployed Cisco 8865 phone running SIP firmware boots, obtains an IP address via DHCP, and successfully downloads its configuration file from the CUCM TFTP server. However, the phone displays 'Registration Rejected' and never registers to CUCM. Packet captures show the phone sends a SIP REGISTER, but the CUCM node it targets is a subscriber that is NOT running the Cisco CallManager service. The phone was manually configured with a single CUCM group containing only that subscriber. What is the most likely cause of the registration failure?

A newly deployed Cisco 8865 SIP phone fails to register with CUCM. Packet captures show the phone sends its REGISTER over UDP to port 5060, but CUCM never responds. Other phones in the same cluster register successfully. The phone's device configuration in CUCM uses a Device Security Profile named 'Non Secure SIP Profile - TCP'. What is the most likely cause of the registration failure?

A SIP trunk connects CUCM to a third-party voicemail gateway. Outbound calls from CUCM to the gateway fail. In a packet capture, CUCM sends an INVITE, the gateway responds with '401 Unauthorized' containing a WWW-Authenticate header, and CUCM immediately sends a CANCEL followed by re-attempting the identical INVITE with no Authorization header. The loop repeats until the call fails. What is the most likely cause?

A newly deployed Cisco IP phone registers successfully to CUCM but every outbound call to the PSTN via a SIP trunk to CUBE fails immediately after the INVITE. In the CUBE debug, the far end returns a '488 Not Acceptable Here' response. The phone is configured with a device pool that uses a region set to allow only G.729 to the SIP trunk device pool, while the ITSP only supports G.711ulaw. What is the most likely cause of the call failure?

A caller on an IP phone reports that when dialing an external number through the CUBE-connected PSTN provider, they hear silence instead of ringback tone until the far end answers. Using 'debug ccsip messages' on CUBE, you observe that the ITSP sends a SIP 183 Session Progress with SDP shortly after the INVITE, but the calling phone never plays local ringback. What is the MOST likely cause of the missing audio during the alerting phase?

A new Cisco IP Phone 8845 is being deployed on a CUCM 12.5 cluster configured for SIP. The phone completes DHCP and downloads its configuration file from TFTP successfully, but never registers. A packet capture on the phone's traffic shows the phone sending a SIP REGISTER to the CUCM subscriber, and CUCM responding with '403 Forbidden'. All other phones of the same model register normally. What is the MOST likely cause?

A collaboration engineer is troubleshooting a one-way call setup failure between CUCM and a partner PBX over a SIP trunk. Using a SIP debug on CUBE, the engineer sees the outbound INVITE reach the partner, but the partner immediately returns a '483 Too Many Hops' response, and the call is torn down. What is the most likely cause of this behavior?