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Logs full of messages like:
Dec 8 07:56:09, SUB1, Error, Cisco CallManager, : 25977: Dec 08 06:56:09.227 UTC : %CCM_CALLMANAGER-CALLMANAGER-3-DeviceTransientConnection: Transient connection attempt. Connecting Port:50453 Device name [Optional].: Device IP address.: Protocol.:SCCP Device type. [Optional]:255 Reason Code [Optional].:6 Cluster ID:StandAloneCluster Node ID:SUB1, 8737

Might indicate one of the following:

  • A device is rehoming in the middle of an registration attempt
  • The second port of your ATA is not configured
  • The IP Phone is not provisioned in CUCM
  • You have VG248’s with unused ports that are not disabled
  • You have VG224’s with unused ports that are not shutdown
  • The network path has issues (firewall messing up SCCP traffic and such)

Basically, it boils down to missing configuration or misconfiguration. For example, if a second port on an ATA tries to register with CUCM, but the CUCM has no configuration for the port, the connection is dropped (hence the transient connection).

Possible solutions are:


  • Disable the second port.
  • Configure the port but don’t assign a DN
  • Configure the port and assign a DN


  • Disable the unused ports on the VG248. By logging in and navigating to configure > Telephony > Port specific parameters, you will see which ports are enabled but do not have a DN assigned.


  • Administratively shut down the unused ports on the VG2248. You’ll have to check in CUCM which ports aren’t used and shut them down accordingly.

Further reading:

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