ISP Modem Router Connecting to Switch or other Device

[Pleh]

Current Setup

ISP Provided Modem/Router > Gateway Device (NIC1 DHCP to ISP router, NIC2 static to ASA) > Cisco ASA > Enterprise Network

The gateway device is basically just a PC with a VPN Cloud service.  The enterprise network sends specific data to it and then forwards it out to the cloud service.  I'm not sure why the setup is outside the ASA, but that's how it needs to be.  The ISP Modem/Router is very restricted and unconfigurable.  It only provides a 4 port LAN with DHCP that you cannot change address.

I need to add three more of the "gateway device" and was wondering what hardware I may need to get it to work.  The goal is for the ISP Modem/Router to connect to another device (probably layer 3 switch or router) through DHCP that has at least 5 ports (1 for the WAN that connects through DHCP ISP Modem/Router, 4 for the devices with it's own DHCP pool that routes out the wan for internet).  I tried to just use a dumb switch but it wouldn't pull DHCP consistently from the ISP Modem/Router for whatever reason.  I also do not want to connect all the devices directly to the ISP Modem/Router because I need to use one of the LAN ports to extend to a different location and wouldn't have enough ports.

I hope I provided enough information.  My question is what device should I use between ISP Modem/Router and ASA -- then the second question would be what would be simple config (or not so simple) for that device?

[pieterh]

for some ISP's the PC needs to "login" into the ISP's network (using PPP or something)
for other ISP's only a single MAC address is allowed through the modem, or they issue only a single DHCP address to the connected device
-> you need to check if this is the case, if so, the ISP only allows a single device and you cannot use the modems multiple ports to connect devices to the internet

The gateway PC is used to hide the network behind it from the ISP (the ISP only sees the PC

if above interpretation of the ISP's network is correct then with enough effort this may be transferred to the ASA or another router that supports PPP

[Georg Pauwen]

Hello, 

I am not really sure I understand what you want your topology to look like. Can you provide a schematic drawing of your desired setup ?

[Pleh]

[Pleh]

The device labeled Cable-Modem-PT is my ISP modem/router that I can't make any changes to.  It gives out IP address via DHCP, and I can't change anything about it.  I have an old 3560 that I tried to use as a dumb switch to connect my four devices I'm calling gateway devices (essentially intel nucs).  They wouldn't pull DHCP addresses from the isp modem/router though.  I don't have any issues from my NUCS to ASA and in my network.  I have a second nic on them that uses static addresses to connect to my ASA.

[Pleh]

Goal is to be able to connect the four gateway devices to a device that gives out dhcp reliably -- which then connects to my ISP modem/router to give them all access to the internet.