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ScreenOS firewall's SCCP ALG does not support version 17



Article ID: KB18226 KB Last Updated: 19 Mar 2015Version: 2.0

Skinny Call Control Protocol (SCCP) version 17 is not supported by the ScreenOS firewall application-level gateway (ALG).


The Skinny Call Control Protocol (SCCP) is a proprietary protocol used by Cisco's CallManager for VoIP. SCCP uses TCP port 2000. IP phones fail to register with CallManager if SCCP ALG is enabled on the firewall.



The ScreenOS firewall SCCP ALG does not recognize the new format of SCCP version 17.

The only workaround is to disable the SCCP ALG on the firewall:

     unset alg sccp enable

No enhancements are planned to address this in ScreenOS.  If customers desire SCCP support, they will have to upgrade to the SRX platform (supported with Junos OS Release 12.1X46-D10 and higher).

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