Cisco 2851 Configuration Examples for Home Broadband Access

Unanswered Question
Aug 2nd, 2009


Does anyone know of any good sites that would have configuration examples or design suggestions for setting up a Cisco 2851 ISR to connect to an SMC 8014 (Comcast Gateway/Cable Modem)? I am trying to setup an use the 2851 as my core router/gateway on the home network. Other than setting up NAT/PAT (I have one static public IP from Comcast), are there any other tips, tricks or suggestions? Any insight is appreicated.



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John Blakley Mon, 08/03/2009 - 10:36


The main thing is if you have a router or a modem from comcast. A router will require you to have comcast support help you put it in bridge mode before your Cisco will be able to use a public address.

That aside, how comfortable are you at the command line?

If your address is truly static and not assigned by your provider on login, then you can assign the address to the interface on the router. Let's assume you have two interfaces: Fa0/0 and Fa0/1 and your internal home network is

conf t

int fa0/0

ip address

int fa0/1

ip address

ip route

You'll need to configure nat as well:

access-list 10 permit ip

ip nat inside source list 10 interfa fast0/0 overload

Put this on fa0/0 and fa0/1:

int fa0/0

ip nat outside

int fa0/1

ip nat inside

That should get you on the internet at least.



matthew5029 Mon, 08/03/2009 - 10:58

Hi John,

Thanks for the quick response. I am comfortable with the command line although I do use the SDM sometimes due to laziness. :)

Comcast provides me with an SMC 8014 router/cable modem which is, I believe in bridge mode already. The SMC currently connects up to my Linksys router. I have a /30 subnet from Comcast, basically one static IP is my address and the other is for the Comcast gateway.

This is good info, thanks again for your help.



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