Proper way to setup multiple public ip addresses with multiple web servers

[landonious]

Hello. We have 3 public ip addresses and 2 web servers. I would like both to be behind the FortiGate but I want to make sure I set it up properly. From what I understand, I am not supposed to use both WAN interfaces and instead I am supposed to assign multiple ip addresses to one interface. If it matters, one of our ip addresses is on one subnet and the other two ip addresses are on a separate subnet. Ideally, the two webservers would use the single ip address and one of the other two. The only reason is that the dns records already point to these two and i don't want to change them if i don't have to. But if it's easier or better to use the two ip addresses that are on the same subnet, I can update everything as needed. I will still be using the same Fortigate and internet connection for all the devices on the network as well. What all do I need to do to set this up properly? Let's say the following:

Public IP address info:

Static Ip 123.45.25.105
Gateway 123.45.25.254
Subnet Mask 255.255.255.0

Static Ip 123.45.24.122
Gateway 123.45.24.254
Subnet Mask 255.255.255.0

Static Ip 123.45.24.123
Gateway 123.45.24.254
Subnet Mask 255.255.255.0

Sales Server 192.168.0.88 (only needs ports 80, 443, 8443) (ideally using public ip 123.45.25.105)

CentOS Server 192.168.1.75 (needs pretty much all ports) (ideally using public ip 123.45.24.122)

The CentOS server sends mail so it MUST use the same ip address for outgoing connections. I suppose I could add all the ip addresses to the spf record if absolutely necessary. But I would prefer to keep it all to one public ip address.

As far as every other device on the network, ideally I would like all traffic for that to use the third unused ip address, but I don't overly care about that part if it's a problem.

[dolunmo2]

You could create virtual interfaces on the host to have multiple IPs with only a single interface, and assign your containers to those, with Traefik or nginx or just plain publishing their ports directly to the IPs of the relevant interfaces.