2 Public IP Addresses on 1 Cable Modem

Hello. I am confused on the topology of how to set this up: I have purchased a static IP from my cable provider to use along with my dynamic IP to run a public server. I currently run NAT behind the dynamic IP for my LAN.

I don't know how to do this with a cable line. With DSL, they provide you with a router usually and all you have to do is plug in your NAT router or computer and configure the network and it works. All I have here is a cable modem. Do I need two routers? Is there one router that I can connect into the cable modem that can support DHCP and NAT on one side and have a fixed static on the other? Confused.

Thanks a lot!

Joe

Reply to
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I'll assume that you've bought a business-level package from your cable company because it's very rare for a cable company to allow servers on their residential accounts. With that detail out of the way, put a switch or a hub immediately behind the cable modem using the uplink port. Connect the WAN port of your NAT router to one port of the switch or hub, and connect your server to another port on the hub or switch.

Reply to
Warren

Joe wrote: "I have purchased a static IP from my cable provider to use along with my dynamic IP to run a public server. I currently run NAT behind the dynamic IP for my LAN."

Are you sure you are getting both the static and dynamic address? The systems I've seen (worked for 2 different companies with 4-5 provisioning systems over the years), will separate multiple IP addresses and multiple IP addresses into 2 lines on the bill. In other words, the static address is one feature, and multiple publics are another. If you are getting multiple public IP addresses, put a switch or hub in front of your nat router, and plug your server into one of the ports, the router in the other.

If, on the other hand, you only have one public IP address and it is configured as a static, you'll need to put your server in a NAT'ed static (192.168.1.x) and enter that number on the DMZ address on the router. In some cases, the cable DHCP server will need the MAC address of your router to make sure you keep getting the same address, even through DHCP.

However, if you have a static IP through Comcast, you have a modem/router provided by Comcast that has all the functionality of a stand-alone router. You just follow the above procedure for one public IP address and go. Your internal subnet is 10.1.10.0, if I remember corectly (haven't looked at one for a few months). You also get your own /30 subnet, and you can run RIP on the gateway/modem (real routing, not just NAT).

Reply to
Eric

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