Configuring DHCP on routers is not something that is normally
done in a production network.  Typically in a production network
DHCP servers are either Windows, Linux, or some other vendors
implementation.  Occasionally you will need to configure a Cisco
device to provided DHCP for initial purposes - say a new location
build-out, a lab network, or even just perhaps for your home
For this post, I will show you how to:
 - Configure your route to be a DHCP Server
 - Configure your router to be a client
 - Configure DHCP Reservations for a specific client
 - Release / Renew your DHCP lease
 - Configure DHCP options (150 for example)
Here is the network information we are going to use:
 Network   -
 Gateway   -
 DNS       - and
 Domain    - FryGuyLab.Net
 Cisco UCM - and
 WINS      -
 Node Type - Hybrid

So, first lets setup the DHCP Server router (R2)
Rack1R2#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Rack1R2(config)#ip dhcp pool DHCP_POOL_1
Rack1R2(dhcp-config)#network /24
Rack1R2(dhcp-config)#domain-name FryGuyBlog.Net
Rack1R2(dhcp-config)#option 150 ip
Rack1R2(dhcp-config)#netbios-node-type h-node

Now, don't forget to exclude addresses if necessary. 
Here will exclude -
Rack1R2(config)#ip dhcp excluded-address
Now we can go over to R1 and configure DHCP and then enable
the G0/0 interface on the router.
Rack1R1#show run int g0/0
Building configuration...
Current configuration : 103 bytes
interface GigabitEthernet0/0
 no ip address
 duplex auto
 speed auto
 media-type rj45

Now we can configure the interface:
Rack1R1(config)#int g0/0
Rack1R1(config-if)#ip address dhcp
Rack1R1(config-if)#no shut
*Nov 15 18:37:55.302: %SYS-5-CONFIG_I: Configured from console
 by console
*Nov 15 18:37:56.102: %LINK-5-CHANGED: Interface GigabitEthernet0/0,
changed state to reset
*Nov 15 18:37:58.866: %LINK-3-UPDOWN: Interface GigabitEthernet0/0,
changed state to up
*Nov 15 18:37:59.866: %LINEPROTO-5-UPDOWN: Line protocol on Interface
GigabitEthernet0/0, changed state to up
*Nov 15 18:38:05.490: %DHCP-6-ADDRESS_ASSIGN: Interface GigabitEthernet0/0
 assigned DHCP address, mask, hostname Rack1R1
As you can see, we received a DHCP address of from the
server. To check the DHCP Lease information on the client, issue the
show dhcp lease command
Rack1R1#show dhcp lease
Temp IP addr:  for peer on Interface: GigabitEthernet0/0
Temp  sub net mask:
 DHCP Lease server:, state: 3 Bound
 DHCP transaction id: 859
 Lease: 86400 secs,  Renewal: 43200 secs,  Rebind: 75600 secs
Temp default-gateway addr:
 Next timer fires after: 11:58:27
 Retry count: 0   Client-ID: cisco-001c.f6e6.6a90-Gi0/0
 Client-ID hex dump: 636973636F2D303031632E663665362E
 Hostname: Rack1R1

Now to check the connectivity, lets PING the other router:

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
To check the active leases on the server, issue the sh ip dhcp
binding command:
Rack1R2#sh ip dhcp binding
Bindings from all pools not associated with VRF:
IP address          Client-ID/              Lease expiration        Type
 Hardware address/
 User name        0063.6973.636f.2d30.    Nov 16 2010 06:25 PM    Automatic
Now for reservations. 
We will configure the DHCP server (R2) to assign
 to R3's F0/0 interface.
On the DHCP Server (R2) - configure a special DHCP pool just
for that client:
Rack1R2#conf t
Rack1R2(config)#ip dhcp pool R3
Rack1R2(config)#client-identifier 0100.0bfd.5661.e0

To find out the Cleint Identifier to use, on R3 look at the Fa0/0
MAC address and then pre-pend 01 to the mac address. 
(see IETF RFC1700 Hardware table below)
Rack1R3#sh int f0/0
FastEthernet0/0 is up, line protocol is up
 Hardware is AmdFE, address is 000b.fd56.61e0
On R3, configure the Fa0/0 interface as follows:
Rack1R3(config)#interface FastEthernet0/0
Rack1R3(config)#ip address dhcp client-id FastEthernet0/0
Rack1R3(config)#no shut
You will then see:
*Mar 13 23:29:28.142: %DHCP-6-ADDRESS_ASSIGN: Interface FastEthernet0/0
assigned DHCP address, mask, hostname Rack1R3
And on R2 you will see under the DHCP binding:
Bindings from all pools not associated with VRF:
IP address          Client-ID/              Lease expiration        Type
 Hardware address/
 User name        0063.6973.636f.2d30.    Nov 16 2010 06:25 PM    Automatic
 302f.30       0100.0bfd.5661.e0       Infinite                Manual

IETF Hardware Table from RFC1700
Number Hardware Type (hrd)                           References
------ -----------------------------------           ----------
 1 Ethernet (10Mb)                                    [JBP]
 2 Experimental Ethernet (3Mb)                        [JBP]
 3 Amateur Radio AX.25                                [PXK]
 4 Proteon ProNET Token Ring                          [JBP]
 5 Chaos                                              [GXP]
 6 IEEE 802 Networks                                  [JBP]
 7 ARCNET                                             [JBP]
 8 Hyperchannel                                       [JBP]
 9 Lanstar                                             [TU]
 10 Autonet Short Address                             [MXB1]
 11 LocalTalk                                         [JKR1]
 12 LocalNet (IBM PCNet or SYTEK LocalNET)             [JXM]
 13 Ultra link                                        [RXD2]
 14 SMDS                                              [GXC1]
 15 Frame Relay                                        [AGM]
 16 Asynchronous Transmission Mode (ATM)              [JXB2]
 17 HDLC                                               [JBP]
 18 Fibre Channel                            [Yakov Rekhter]
 19 Asynchronous Transmission Mode (ATM)      [Mark Laubach]
 20 Serial Line                                        [JBP]
 21 Asynchronous Transmission Mode (ATM)              [MXB1]
Now, if you need to force release an IP address on a client, you can issue the command:
Rack1R1# release dhcp g0/0

If you need to renew the address, you can use the command
Rack1R1# renew dhcp g0/0