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How to set up a Cisco Router 2800 as DHCP and Internet Gateway

How to set up a Cisco Router 2800 as DHCP and Internet Gateway

I have a Cisco Router 2800 Series and I would like to set it up as my DHCP Server and Internet Gateway. Because its OS has security features I would like to use it as my firewall and traffic controller.

My router has only two fast Ethernet connections. F0/0 and F1/0

I know the very basic interface configuration for each interface but can I use F0/0 to be my internet gateway and F1/0 my LAN Interface?

I have a T1 as ISP.

Currently I have the T1 going straight to my SBS 2003 server. In my server I have two NIC cards one as Wan Connection and the LAN. I need to independently place DHCP and Internet connection in this router so I can have my server only taking care of my Database and Access List.

Is it possible to accomplish this with this router and only two fast Ethernet connections?

Beside the basic configuration of:

CONFIG T
INTERFACE F0/0
IP ADDRESS 219.253.XXX.XX
DESCRIPTION WAN GATEWAY
NO SHOUTDOWN

INTERFACE F1/0
IP ADDRESS 192.168.0.1
DESCRIPTION LAN GATEWAY
NO SHOUTDOWN

Plus the enable passwords, what else I need to do?


How do I put the DNS and activate DHCP.


If after the set up is successful, my LAN defaults gateway and DNS will be?
Avatar of Don Johnston
Don Johnston
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I'm a little confused about your T1 line going to a NIC on your server. T1 lines can't connect to ethernet ports. I'm guessing that whatever service you have is being presented to you as ethernet.

You'll also need a default route.

So you're starting config would be something along the lines of:

ip dhcp excluded-address 192.168.0.1 192.168.0.10
ip dhcp pool <name>
 network 192.168.0.0 255.255.255.0
 dns server x.x.x.x
 default route 192.168.0.1

int f0/0
ip address 219.253.XXX.XX 255.255.255.xxx
description WAN Gateway
no shut

int F1/0
ip address 192.168.0.1 255.255.255.0
description LAN Gateway
no shut

ip route 0.0.0.0 0.0.0.0 219.253.???.???
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cyborgcom

ASKER

Hi donjohnston,

Answering to your question, the T1 goes to an Adtran Modem and then to my SBS 2003 NIC

The other questions are, is it possible to copy the routing table from my current DHCP and place it to the Cisco Router? Or I have to release every IP Address in my clients to generate a new table in the Router.

I am planning to use static IPs from 10 to 89 and 140 to 149, then the rest will be dynamic.

I will put your instructions to work tonight, thank you so much for your help.
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Avatar of Don Johnston
Don Johnston
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I have this configuration to make my 2800 Cisco Series Router my WAN Gateway, LAN and DHCP

ip dhcp excluded-address 192.168.0.1 192.168.0.10
ip dhcp pool <name>
 network 192.168.0.0 255.255.255.0
 dns server x.x.x.x
 default route 192.168.0.1

int f0/0
ip address 219.253.XXX.XX 255.255.255.xxx
description WAN Gateway
no shut

int F1/0
ip address 192.168.0.1 255.255.255.0
description LAN Gateway
no shut

ip route 0.0.0.0 0.0.0.0 219.253.???.???

I have been able to entered all the commmand lines except for:

dns server x.x.x.x

and

default route 192.168.0.1

In this last command the router keeps telling me the address is ambiguous.

In witch configuration mode I have to excecute dns server x.x.x.x command and if my LAN Interface has the 192.168.0.1 255.255.255.0 should that be in --> default route 192.168.0.1