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I need help setting up my 2811 to do basic routing.

I have been given the task of setting up a 2811 to handle basic routing.  

We have a business cable modem account with 5 static addresses assigned to that account.  For us to get on to the internet we have to use one of those static addresses.  The static addresses are class A addresses with a submask of and they also have static class A dns addresses.  Our internal addresses are also class A addresses with a subnet of and are mixed between static and dhcp addresses.  

All I would like help doing is getting my modem connected to the 2811 to provide internet connection to my network.  It seem straight forward but I can't seem to get that to happen and I'm not very familiar with IOS but learning a lot now.

Any help would be appreciated greatly.  

Here is the version of this server if it helps in any way.

Cisco IOS Software, 2800 Software (C2800NM-IPBASE-M), Version 12.4(15)T10, RELEASE SOFTWARE (fc3)
Technical Support:
Copyright (c) 1986-2009 by Cisco Systems, Inc.
Compiled Mon 14-Sep-09 14:01 by prod_rel_team

ROM: System Bootstrap, Version 12.4(13r)T11, RELEASE SOFTWARE (fc1)

router uptime is 32 minutes
System returned to ROM by reload at 03:33:43 UTC Sat May 8 2004
System image file is "flash:c2800nm-ipbase-mz.124-15.T10.bin"

Cisco 2811 (revision 53.50) with 251904K/10240K bytes of memory.
Processor board ID FTX1344AHYJ
2 FastEthernet interfaces
DRAM configuration is 64 bits wide with parity enabled.
239K bytes of non-volatile configuration memory.
62720K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0x2102



Can you post the full config of your router?

To enable routing (the command ip routing should be used although not normally necessary on a router), you also need routes in your routing table. A good starting point is a default route pointing to either the next-hop address or exit interface (p2p only I believe). So you would need to do this:

conf t

ip route x.x.x.x/int where x.x.x.x = next hop address, int = exit interface.


Dan Miley

Are you doing nat to the cable modem, or is the cable modem doing nat? 

Are there public IPs on the cable modem side, or private IPs on the wan side of the router?

The 2811 will need a default gateway pointing to the cable router,  the cable router will need routes to networks that are behind the 2811.

At the bottom of this post is how to create static and other routes, dhcp scope for the lan side, etc.


If you need to do nat in the device you will need to have some nat statements.  Here's a guide for getting started, this is for a 2500 series, but it should work the same.

Hope this helps,

it would be great if you tag helpful posts,