Multiple WAN interfaces in same subnet on Sonicwall NSA220

sonicwallwide-area-network

(eta salutation, which keeps getting eaten.)

Hi, all.

I see a bunch of related questions, so I'm hesitant to ask, but:

I have a situation where I have a Sonicwall NSA220 serving as firewall/router for two internal subnets to two external WAN connections. In some locations this is two separate ISPs. In others, it's the same ISP but with multiple circuits.

The problem is that one ISP has been unable to provide unique subnets for each WAN interface.

Is there any possibility that I might be able to bond the two WAN interfaces into a single virtual interface, and then use source-routing to get internal subnets communicating out the appropriate physical interface? Or even just use traffic-shaping to give each internal network appropriate shared bandwidth? I haven't found anything in the docs, but it seemed like it might be worth asking.

Thanks for any help!
-Steve.

Best Answer

You may try the following setup:

Install a switch in front of SW and connect two ISP connections from the same subnet).

ISP link 1------
                |--switch---|--sonicwall--|----LAN
ISP link 2 -----

On SW, assign a WAN IP from the same subnet.

Is WAN Gateway same for both Links?

If there are two, you may be able to setup two outbound routes for each Link.

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I believe you should be able to use the routing table to accomplish this. Essentially, the Network->Routing tab should let you create routes for your two networks. I think a rule from the LAN source, to any IP, should use the default gateway for your cable interface. Then a second rule stating that any traffic from the VOIP network, to any destination, should use the fiber default gateway. I'm hoping each of these networks is distinct in logical and hopefully physical ways, as that would make things a little easier.

You can definitely back this up with firewall rules only allowing traffic between the proper networks. But firewall rules won't actually direct traffic where you want it to go, it will only stop it from going where you don't want.

And, of course, you'll probably want to use the packet sniffer to verify everything's doing what you want it to.

--Christopher Karel

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If you don't have NAT rules specifically handling traffic from internal subnets (generally called Firewalled Subnets) to external IPs of those internal machines, you need them. In my config they go something like this:

Original Source: Firewalled Subnets  
Translated Source: [public IP of server]   
Original Destination: [public IP of server]   
Translated Destination: [private IP of server]

Best Answer

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