I asked this question on the Sonicwall forums and user “wennjackjoy” was kind enough to answer it for me. Thanks again!
The customer has a Sonicwall which has two Internet interfaces, I have failover configured and the primary interface is an ADSL (WAN) connection with loads of bandwidth.
He also has a SDSL much less bandwidth but much more reliable. I want to send all SIP traffic over the clean and reliable SDSL line. (OPT)
How can I force all SIP traffic or data to that specific IP over that interface (WAN)?
Assuming that you have Sonicwall Enhanced OS:
Under ‘Interfaces’ setup the OPT port to be in the WAN Zone
Go to Address Objects, setup a single item, call it SDSL GW and setup the OPT GW address. If you want to route only certain SIP devices over the SDSL, this is the time to do it.
Under routing, setup a rule:
Source: LAN Subnets
Gateway: SDSL GW
Voilà apply settings and it should work. If you want to test that the rule is working, go ahead and change Service from SIP to HTTP and go to: whatismyip.com or myip.dk.
Enabling Consistent NAT and SIP Transformation is a great way to make sure that those SIP packets don’t get lost is Network-Address-Translation.