Hello everyone and thank you for your comments ahead of time.

I have a Fiber ethernet connection from Comcast that is a layer 3.
I like to know if its possible with IPTABLES to create a firewall router with it using these parameters.

ISP: Layer 3 P2P /30
Gateway: 51.226.133.1
Netmask: 255.255.255.252
Layer 3 usable IP customer end: 51.226.133.2

ISP NAT POOL: /27
Range: 51.226.132.224/27
Usable Range: 51.226.132.225-254
Netmask: 255.255.255.224

Private Network IPs:
172.30.0.x/22 (Separate switch)
10.30.0.x/22 (Separate switch)
10.1.1.x/22 (Separate switch)

System Network adapters:
eth0(51.226.133.2)ISP
eth1(172.30.0.1)Network1
eth2(10.30.0.1)Network2
eth3(10.1.1.1)Office

So I can get IPTABLES to work with the first part but cant find information on the NAT Pool.
The NAT Pool will map to various resources www dns sftp ect....
Looking for a clean approach.
Thoughts?

I noticed your posting both here (with a SOLVED tag) and the one referencing KarlRupp NAT_Tutorial that AwesomeMachine replied to you with.

What (if you want to) did you do to configure your 4 NIC box to make it a Layer 3 switch to work with Comcast Fiber?

Do your static assigned IPs reply as their assigned or just from the primary IP (since I assume you are using sub-interfaces)?

Also, did try putting another physical device (IoT, computer, etc) on the outside of your Linux box (via a layer 2 switch) connecting the Comcast fiber ethernet hand off to the layer 2 switch and then your Linux box and other physical device plugged into that switch?

Security concerns put aside for the testing purposes, what has your experience been with the Layer 3 switch config and environment testing?

Just got our fiber installed and prefer a Linux solutions versus purchasing a Layer 3 switch just to make full use of our Comcast service.

Thanks!