This document will cover SonicOS Enhanced 6.5.x.x. Version 5 will be slightly different.
(Note:The CLI config is basically the same I just find it easier to use the GUI when writing NAT polices than having to write down and remember the many different address objects and services you are dealing with)
1.
Create address objects that reference all SIP server hosts before you begin to configure any NAT polices.
2.
Create a Custom Service Object specifically for SIP UDP 5060. The default SIP service object in SonicWall is geared toward port ranges, so you will want to create a new custom object.
3. Start building your NAT polices. I start from the outside:inside or ingress in
the X1 interface and create a reflexive policy
4.
Next, make sure your reflexive policy from
the inside:outside has the proper address and service objects.
5. Capture traffic to make sure your new NAT/PAT policies have applied. Please note that this may take a few minutes to settle down if you have existing connections to SIP servers.