Configure DHCP on Cisco Routers

When you are running a very small business, you often don’t have the time to mess with having a centralized windows or mac directory server handle your DHCP for you.  In these cases, if you happen to have a Cisco router, you can configure DHCP on your Cisco router so that it will manage the DHCP services for you.  Here’s how you would configure dhcp on cisco routers:

Step 1 – ssh login, get on the console, or use telnet if that is enabled to the cisco router

# ssh -l <username> <ipaddress of the Cisco router>

Step 2 – Enter configuration mode 

myrouter# config t

Step 3 – Configure the network addresses that will not be assigned to DHCP clients:

myrouter(config)# ip dhcp excluded-address 10.2.30.1 10.2.30.31

Step 4 – Configure the DHCP Pool – including the network, domain-name, dns-servers, the default router and the length of the lease:

ip dhcp pool MYDHCPPOOL
network 10.2.30.0 255.255.255.0
domain-name mydomain.com
dns-server 208.67.222.222 208.67.220.220
default-router 10.2.30.1
lease 0 12

Step 5 – Save the router configuration for the next boot:

myrouter(config)# exit
myrouter# wr mem

That’s it.  It should be up and working.  Please be careful not to have 2 different servers supplying DHCP addresses on the same network.  This will get very confusing for all of the DHCP clients and will likely cause a broadcast storm leading to nothing working well on your network.  If this does occur to you, simply assign your workstation a static address and log back into the router and change the first command in step 4 to be:

myrouter(config)# no dhcp pool MYDHCPPOOL

which should turn off dhcp on your router until you can turn off DHCP on the other DHCP server.

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Jeff Staten

Jeff has 20 years of professional IT experience, having done nearly everything in his roles of IT consultant, Systems Integrator, Systems Engineer, CNOC Engineer, Systems Administrator, Network Systems Administrator, and IT Director. If there is one thing he knows for sure, it is that there is always a simple answer to every IT problem and that downtime begins with complexity. Seasoned IT professional by day, Jeff hopes to help other IT professionals by blogging about his experiences at night on his blog: http://uptimemadeeasy.com. You can find Jeff on Google+ or LinkedIn at: LinkedIn or Twitter at: Twitter

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