PAT on a MX84

[Bred_85]

Hello,

I have a Meraki MX84 that is now going to be directly connected to an internet line directly via the Internet 1 port. Unfortunately I have only been given one usable IP. I have another firewall that requires outbound internet. My question is how can I setup what was basically a PAT interface on other cisco devices (such as an ASA). 

Do I just add the outside interface of the FW into a LAN interface on the MX and it will just work? Or do I need to setup a PAT (which I cannot find any documentation for). 

Thanks in advance

Brenden 

[alemabrahao]

You can set the outbound interface in one of Mx lan and use Mx as a default gateway.

[KarstenI]

How much separation do you need? And is it really only outbound traffic or also inbound?

If it is only outbound, do you really need the old firewall or can you just configure a VLAN with the subnet of the old firewall and replace the old device?

For Internet-access, PAT is done automatically when you send  traffic to the MX on a LAN interface.