IOS DHCP Server reservation (Windows and linux)

Unanswered Question

Hi There,

I have a dual boot laptop that I want to get the same IP address whether it boots to Windows or linux.

I have it working in Windows with the following


ip dhcp pool Laptop


client-identifier 0100.0fb0.463c.1b


However because windows seems to need "01" before the ACTUAL MAC address, and linux does not, then I do not get the same IP.

Is this possible?



I have this problem too.
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Rolf Fischer Wed, 02/21/2007 - 03:43

From my point of view it depends only on the Ethernet-Type used by the NIC, not the OS.

On the other hand, DHCP is a process controlled by the OS and the OS may have to decide which Ethernet-Type is used for encapsulation.

> Specifies the unique identifier for DHCP clients. This command is used for DHCP requests.

> DHCP clients require client identifiers. The unique identification of the client is specified in dotted hexadecimal notation, for example, 01b7.0813.8811.66, where 01 represents the Ethernet media type.


Hope that helps,


Rolf Fischer Wed, 02/21/2007 - 04:38

Found this value-list in RFC 1700:

Number Hardware Type (hrd)

------ -----------------------------

1 Ethernet (10Mb)

2 Experimental Ethernet (3Mb)

3 Amateur Radio AX.25

4 Proteon ProNET Token Ring

5 Chaos

6 IEEE 802 Networks


8 Hyperchannel

9 Lanstar

Maybe a debug-command shows different frame-types?

Hard to believe that the MAC-Address is different if you boot Linux.

Rolf Fischer Thu, 02/22/2007 - 09:14

I played a little bit with Wireshark and watched the DHCP-Discovers from a Windows XP PC and those from a SuSe-Linux PC.

Both OS used Ethernet II frames!

Because of this result I'd recommend debugging DHCP on the Cisco-Switch.

mkonarski3 Thu, 02/22/2007 - 17:16

use "hardware-address" (don't put the 01 in front just the mac addr xxxx.xxxx.xxxx) for your unix box and "client-identifier" for your windows box, as far as i know you can't have both on the same "ip dhcp pool" and if you create a different pool for the same host ip so you can put "hardware-address" command in you will get an error "% A binding already exists..." because you're assigning the same ip to different pools

hope this makes sense, mike




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