Sunday, July 8, 2012

Using Cisco Switches As A DHCP Server

On occasion, I do use Cisco switches as a DHCP server on the network.  There are a few reasons why you might do this.  I take the view that if the Microsoft DHCP server dies, you still have the network.  You just have to rebuild a DHCP server somewhere.  However, if your core switch dies and it does DHCP also, its not like DHCP is your primary concern at that point.  If you don't have a core, you don't have anything really.  Here is a configuration example I used at a customer site, along with notes to tell what it does.

ip dhcp excluded-address  <--- This address range gets excluded from being handed out.

ip dhcp pool Data                                           <---  This pool's name is "Data".
   network     <--- This is the network that DHCP will hand out for.
   default-router     <--- This is the default gateway for the devices getting an IP address from this scope.
   dns-server                          <--- DNS server.
   netbios-name-server             <--- WINS server.
   option 150 ip                           <--- Option 150 is for Cisco phones.  You dont need this for data networks.