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cisco 2600 series router & cable modem

I need to connect a cable modem to a Cisco 2600 series router. The Cisco router should allow network users to share the cable connection. One port will be direct connect to the modem, the other port of the router will be connected to hub, which then connect to workstations.

The router has 2 ethernet ports and the version is 11.3(10)T.

Can anyone tell me how to set all of this up as im only a newbie at all this.

Thanks John

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Re: cisco 2600 series router & cable modem


First, I'd try to get ahold of a newer IOS for comfort sake.. 12.1(1)T is a safe bet. Never hurts to upgrade if you can. There are no bugs in this IOS related to what you want to do.

If you're considering runing NAT and DHCP on your LAN, you could set up a NAT and DHCP pool and give out addresses to you hosts..

Here's how I'd do it... (feel free to hammer me if I'm wrong people)..

1. Decide on your internal addressing. Let's say you choose as your internal NAT and DHCP pool.

2. Configure the DHCP Pool:

no ip dhcp conflict logging

ip dhcp excluded-address (your internal NAT address should be this)


ip dhcp pool SOMENAME


domain-name YOUR_DOMAIN



lease 3

3. Configure your NAT Pool:

interface EthernetX (connected to your modem)


ip nat outside


interface EthernetY (what's connected to your LAN)

ip addr

ip nat inside


ip nat pool HideMe YOUR PROVIDED IP YOUR PROVIDED IP prefix-length 24

ip nat inside source list 1 pool HideMe overload

ip classless

ip route EthernetX

no ip http server


A couple considerations...

1. Make sure you use AAA and an access-class on your VTY ports to hinder bad guys from telneting to your router.

2. If you have additional IPs already, you may want to go that route instead of NAT sice some applications i.e. MSN Messenger (voice/video) and other applications don't play well with NAT.

3. If you're running any servers behind your router, you'll want to use static address on it and make sure you exclude that in your DHCP pool.

4. Make sure you employ access lists to prevent unwanted traffic and a distribute-list on your ethernet port to block routes from being advertised to your ISP. That should happpen anyway, but it never hurts to be certain..

5. If you use this config, you might want to configure your LAN win clients to automatically get an IP, but hardcode the DNS server into the config. I've seen problems with this on other routers, but never Cisco. Still, that may be an issue if your LAN isn't getting DNS resolution..

This should get you started.... Good Luck!!


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Re: cisco 2600 series router & cable modem

Thanks for that Brent, but how do i get hold of a newer ios?

Community Member

Re: cisco 2600 series router & cable modem

If you have a cisco maintenance agreement, you can

go to the software center on the home page and download from there.

Community Member

Re: cisco 2600 series router & cable modem

what if i dont though? there must be a way of updating this thing :( Even if someone can send me the file


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