I'm nervous leaving the device like this because it makes no sense to me WHY it's working like this.
We put in the new Sonicwall to replace an older Cisco ASA.
Just did the basic setup, using same IP's from the ASA: (making up IP's here but using same subnets)
X0 LAN: 172.16.5.2/30
X1 WAN: 216.40.5.100/30
Then I add route for one of their internal subnets...
10.1.0.0/16 to gateway 172.16.5.1 on X0 LAN port (172.16.5.1 is MPLS provider router, which has route going to 10.1.0.0 network)
So, I set this up. Doesn't work. 10.1.0.0 network can't ping the Sonicwall and can't get onto the internet, Sonicwall can't ping 10.1.0.0 network.
NOW, just to test something, I turned on the X2 port on the Sonicwall, and put it into Layer 2 Bridge mode, and bound it to the X0 LAN port. I don't connect anything to X2, just enabled the bridge - X0 LAN and X1 WAN are still the only ports being used. Magically, everything starts working. I added in additional routes for more internal networks, setup necessary firewall/nat rules, everything works 100%.
If I turn off port X2 and remove the bridge, everything goes down.
I'm completely stumped as to why adding this bridge, which is seemingly useless, would make things work here. Mind you, there was no bridging setup on the Cisco. I've setup many a Sonicwall and never had a similar situation.
Here's a screenshot of the interfaces.