2 Public IP Addresses on 1 Cable Modem

2 Public IP Addresses on 1 Cable Modem
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2 Public IP Addresses on 1 Cable Modem jfjfjfkkkkkk111111 03-16-2006
Posted by on March 16, 2006, 1:47 pm
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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


Posted by Warren on March 17, 2006, 12:49 am
jfjfjfkkkkkk111111@yahoo.com wrote:
> 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.

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.

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Power Lawncare Tools for Spring Clean-up:
http://www.holzemville.com/mall/blackanddecker/




Posted by Eric on April 14, 2006, 12:58 am
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).


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other useful resources:
The Federal Communications Commission (FCC)
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