DHCP Static Binding on Cisco IOS

This topic is to discuss the following lesson:

Thanks for the info Rene
As always complete posts!

how to reserve a single ip for pc in router ? ?

That is exactly what this lesson is about…

Hi Rene

I have some challenges with CCNA R&S lab about DHCP/DHCP relay.The lab number is assuming that you have access to the new CCNA R&S oficial course…
The lab has two clients, two intermediary routers and another router connected to the intermediary routers via serials.
Intermediary router are R1 and R3, the central router is R2.
To R2 are connected via Ethernet GIgabit interfaces a DNS Seriver and the ISP
The lab tell me to do the R2 a dhcp server for the two PC’s connected to the intermediary routers R1 and R2 so they receive an IP…
The challenge is i just can’t get the “ip helper addresses” correct for R1 and R3 to relay the DHCP ip allocation from R2…Neither here or in your book i found what i am looking for…

Thank you

Hi Catalin,

Your message wasn’t deleted but not approeved before, I do this manually because of spam. I think this example should help you:

If not, let me know.


Awesome Post!!!

Thanks Jose!

Hello Rene,

Is the client-identifier configured on the dhcp server is not the mac address of the dhcp client? Is it a different value?(real world)

I tried to configure the “ip address dhcp client-id fa0/0” on the dhcp client but it’s not getting the correct ip im expecting. I already have a dhcp pool for it on the dhcp server.:


R1#SHOW RUN | sec ip dhcp
no ip dhcp use vrf connected
ip dhcp pool DONDRUJA
   option 150 ip
   lease 2
ip dhcp pool PC2
   client-identifier 2222.2222.2222
ip dhcp pool R3
   hardware-address 4444.4444.4444


Building configuration...

Current configuration : 136 bytes
interface FastEthernet0/0
 mac-address 2222.2222.2222
 ip address dhcp client-id FastEthernet0/0
 no ip route-cache
 duplex half

Hi Don,

It’s probably the DHCP client that is bugging you. Take a look here:


Hi Rene,

For the DHCP client in cisco router, there’s option to put the hostname. What the purpose to put the hostname?

R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address dhcp client-id fastEthernet 0/0 hostname R1


Hi Davis,

You could use this as an identifier. The DHCP server could be configured to assign an IP address based on the hostname.


Can you configure multiple static bindings in the same pool?

Hello Chris

Yes you can. Just add additional host commands within the DHCP pool.

I hope this has been helpful!


Something else I just noticed - it seems Windows 7 will prepend “01” on to the start of the MAC as the client identifier

Hello Chris.

Yes, this is the case. Windows 7 as well as other operating systems as well as firmwares of network devices will implement a client identifier based on RFC4361.

I hope this has been helpful!