Sometimes when I learn something new in the world of technology, I am often amazed that something that I assumed was technically advanced is rather quite simple.
Such is the case with configuring DHCP on a Cisco Router. I mean, is it just me or do network guys sometimes act as if everything that they do is takes elite technical skills and tons of experience. Don’t get me wrong, I know that networking is not exactly easy. But can we just agree to admit that once in a while some things are easier done than said. Anyway, for me this was the case with configuring a DHCP pool on a Cisco Router.
In this instance I was working on getting a new virtual machine up and running on my ESXi host. This particular appliance needed to boot via dhcp so you could access its web interface. So I jumped on my 2621xm and created the pool.
First we enable the dhcp service
r-2621-1(config)#service dhcp
Then we create a pool
r-2621-1(config)#ip dhcp pool LabPool
r-2621-1(dhcp-config)#network 10.2.0.1 255.255.255.0
Next we set a few bits and bobbles so that clients can route.
r-2621-1(dhcp-config)#dns-server 10.2.0.71
r-2621-1(dhcp-config)#default-router 10.2.0.1
r-2621-1(dhcp-config)#domain-name localdomain
In this case I wanted to exclude a bunch of ips from the range
r-2621-1(dhcp-config)#ip dhcp excluded-address 10.2.0.1 10.2.0.100
Now save your config with copy run start.
The command below shows me all my dhcp clients
r-2621-1#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
10.2.0.101 0050.569a.7dbe Oct 16 2013 11:21 PM Automatic
This handy command shows me information pertaining to my pool
r-2621-1#show ip dhcp pool
Pool LabPool :
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 1
Pending event : none
1 subnet is currently in the pool :
Current index IP address range Leased addresses
10.2.0.102 10.2.0.1 – 10.2.0.254 1
r-2621-1#show ip dhcp conflict
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