[SIPForum-discussion] NAT issue in Enterprise network

[Mark R Lindsey]

SIP wasn't designed to be NAT-friendly; NAT imposes many limitations  
generally incompatible with the full breadth of design goals of SIP.  
You should expect SIP to NOT work when NAT is involved UNLESS you use  
some NAT traversal mechanism.

There has been a lot of work done here; Section 6 of the SIP  
Hitchhikers Guide has several references to proposed and implemented  
solutions to NAT traversal.

http://tools.ietf.org/html/draft-ietf-sip-hitchhikers-guide-06#section-6

In addition to what's listed there, the Session Border Controller  
Functions IETF draft describes a very popular approach (SBCs) for NAT  
traversal:

http://www.ietf.org/id/draft-ietf-sipping-sbc-funcs-08.txt

Most service providers in the US who offer service to SIP phones will  
operate an SBC to enable their customers to use NAT'd SIP phones.

Good luck!

On Sep 10, 2009, at 2:00 AM, Manish Jain wrote:

> Hello All,
>
> There are issues arising when using the soft phone (Bria, X- 
> Lite ...etc), All Soft & Hard Phones are behind NAT.
> Issues are : No Incoming calls on soft phone from any soft/hard phones
> No Outgoing calls to soft Phone but able to make calls on Video/IP  
> Phones.
>
> There is absolutely no problem observed with the Video/IP Phones for  
> making and  receiving the calls.
> I am not sure what could be the issues, Any help/suggestion would be  
> helpful.
>
> -- 
> With Regards,
> Manish Jain
>
> Luck Is Like a Blank Paper,where we writes our Future.
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mark r lindsey at e-c-group.com http://e-c-group.com/~lindsey +12293160013