SBS 2003 IP address

More info about your network will probably be needed.  Considering that your SBS server only has 1 nic, I'm going to assume it's not your network firewall/gateway correct?  What are you currently using?

You can probably make this happen pretty easily using an advanced firewall or firewall OS like pfSense and/or VLANs.

When you say the VoIP system is requesting that specific gateway, you're talking about an internet gateway right?  We're not talking about a private gateway for SIP trunking or anything similar correct?

Correct, we have one NIC in the server and we're running a Sonicwall NSA240.

I did some checking on VLANs and thought I seen something about not being able to setup VLANs on an SBS?

Correct, I'm guessing they're just looking for an Internet gateway.

Clarification:  Could assign a secondary IP addy to your SBS NIC.  This could cause DNS issues though if SBS is setup to automatically update DNS based on interface IP addresses.  It may cause resolution of your SBS servers name to point to the wrong IP.

Please do not add an IP to the SBS NIC. You can do so with Server std, but SBS does not "like" multi-homed NIC's.
I assume also 192.158.42.254 is a typo and it should be 192.168.42.254 as the former is a public IP.
Though the Sonicwall will probably support multiple public IP's I am doubtful it may not multiple LAN IP's. An inexpensive option is to add a second router, which would have a different public IP and LAN IP. Though these can co-exist on the same LAN, a router that supports VLans would be a better option. The problem with this is you cannot have 2 DHCP servers so your VoIP systems would need static IP's.

Why are they asking to use a gateway of 192.168.42.254? Have they installed a second router? I can't imagine they pulled that address "out of the air".
It is more common to use a shared gateway, but put the VoIP devices on a separate VLAN and use QoS to maintain stability.

I wouldn't add a second router.  I'd replace the Sonicwall if it can't do multiple lan subnets.  pfSense is able to do this without issue and only requires one WAN connection and one public IP.  You would then be able to do DHCP on both LAN subnets if needed.  I've done this setup in many different offices and it works fantastically.  You'll also be able to shape traffic with it to assure bandwidth is available for the VoIP traffic.  Just make sure you keep your phone and computer networks separate to avoid DHCP nightmares.

Although you would lose all the cool Sonicwall features.  Multiple routers just rubs me the wrong way but it may be unavoidable.  I sometimes forget that Sonicwalls can do more than just route traffic. ;)

**Update**

So I went back to the VoIP provider and asked why they needed a gateway IP of 192.168.42.254 and was told that was the address of the PBX.
I was told that another option is to setup DHCP options on the SBS with the following information: Code 242, ascii string “MCIPADD=192.168.42.1, MCPORT=1719,HTTPSRVR=192.168.42.1, L2QVLAN=2, VLANTEST=900”

Since the SBS is running on IP 192.168.5.10 (DHCP SCOPE 5.50-5.150) do I have the ability to setup a DHCP option using a different gateway as requested and not have any problems?  Or could I setup Code 242 and point it to a static IP like 192.168.5.15 and keep everything under the current scope?

Thanks!

The VoIP provider dropped a second NIC in the PBX

Thanks for your help!