[cisco-voip] Cisco SIP Phones - Ephemeral Source Ports

[Ryan Ratliff (rratliff)]

Our documentation on TCP/USP port usage is for the destination port.  It's not uncommon at all for clients to source from an ephemeral port when initiating a connection to a server. 

-Ryan

On Nov 14, 2013, at 5:37 AM, Boon <ciscovoipuser at gmail.com> wrote:

Hi, 

I ran into a peculiar issue last week where I had to advise a client on firewall rules related to Cisco Phones running a SIP firmware image. 

I was surprised to find that Cisco phones use an ephemeral source port instead of 5060. Therefore for CUCM initiated SIP messages to phones the destination port is from this ephemeral range. 

Could somebody point me towards the documentation or release notes that specify the use of this range of ports? Has it always been this way?

Unless I'm mistaken the CUCM TCP/IP Port Usage guide has always shown 5060 for CUCM-SIP Phone signalling.

Thanks
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