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DHCP Client that can change default Vendor Code (60) from MSFT 5.0

Posted on 2008-10-01
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Last Modified: 2008-11-08
The Microsoft Windows XP DHCP Client sends "MSFT 5.0" for DHCP Option 60 (Vendor Code).

I need to change the Vendor Code in a DHCP Discover Request on a Windows XP PC.

Is there a way to do this with in Windows Directly?

Is there a 3rd party client that can do this?

Thanx!
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Question by:xq1xq1xq1
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Expert Comment

by:Kenneniah
ID: 22623229
More than likely not. The Vendor Code isn't something Windows XP sends, but rather the hardware.
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LVL 24

Expert Comment

by:Kenneniah
ID: 22623316
To explain a little more, the Vendor Code is the first half of the MAC address, which is of course hard wired into the NIC. Of course you can look into MAC address spoofing tools, but not sure if any would work in your situation or not.
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Author Comment

by:xq1xq1xq1
ID: 22642010
Thanks for the suggestions so far.

I believe there is confustion regarding DHCP Discover Option 60 and the OUI of the MAC address which is burned into the NIC card by the Manufacturer.

What I am looking for is changing Option 60 sent in the DHCP Discover Message.

Please refer to the Packet Decode of a DHCP Discover packet:

No.     Time        Source                Destination           Protocol Info
     23 16.206762   0.0.0.0               255.255.255.255       DHCP     DHCP Discover - Transaction ID 0x4288cd2e

Frame 23 (342 bytes on wire, 342 bytes captured)
Ethernet II, Src: AsustekC_75:e4:aa (00:15:f2:75:e4:aa), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Internet Protocol, Src: 0.0.0.0 (0.0.0.0), Dst: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootpc (68), Dst Port: bootps (67)
Bootstrap Protocol
    Message type: Boot Request (1)
    Hardware type: Ethernet
    Hardware address length: 6
    Hops: 0
    Transaction ID: 0x4288cd2e
    Seconds elapsed: 0
    Bootp flags: 0x0000 (Unicast)
    Client IP address: 0.0.0.0 (0.0.0.0)
    Your (client) IP address: 0.0.0.0 (0.0.0.0)
    Next server IP address: 0.0.0.0 (0.0.0.0)
    Relay agent IP address: 0.0.0.0 (0.0.0.0)
    Client MAC address: AsustekC_75:e4:aa (00:15:f2:75:e4:aa)
    Server host name not given
    Boot file name not given
    Option: (t=53,l=1) DHCP Message Type = DHCP Discover
    Option: (t=116,l=1) DHCP Auto-Configuration
    Option: (t=61,l=7) Client identifier
    Option: (t=50,l=4) Requested IP Address = 172.27.84.111
    Option: (t=12,l=7) Host Name = "AMD3500"
    Option: (t=60,l=8) Vendor class identifier = "MSFT 5.0"
    Option: (t=55,l=11) Parameter Request List
    Option: (t=43,l=2) Vendor-Specific Information
    End Option
    Padding
I need to change the line denoted by Option (i=60,I=8) Vendor Class Identifier as MSFT 5.0.

Hope this clarifies the issue.

Thanx!
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Author Comment

by:xq1xq1xq1
ID: 22642024
To further clarify, I need to change MSFT 5.0 to a custom string sent out in Option 60.
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LVL 24

Assisted Solution

by:Kenneniah
Kenneniah earned 20 total points
ID: 22643607
Ahh, ok so you are looking for Vendor Class, not Vendor Code. Unfortunately that's also hardcoded, but into the client. In this case "dhcpcsvc.dll". It would be possible for someone good at altering dlls to change it I would think, but unfortunately that's not me. I'm also not aware of any good way to replace the DHCP client with another, so will just have to wish you good luck!
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Author Comment

by:xq1xq1xq1
ID: 22646161
Yes you are right - I miss identified the name of the option which is why the decode was worth 'a thousand words'.

I know that the Vendor Class for the Microsoft DHCP Client is embedded in the Microsoft DLL.

What I am trying to determine is where to download or how to recreate a 3rd party DHCP client that will run under Windows that I can customize the Vendor Class with.

Thanx for your time and attention to this matter!
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Accepted Solution

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xq1xq1xq1 earned 0 total points
ID: 22737278
I will leave this question open for 1 more week.
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Author Comment

by:xq1xq1xq1
ID: 22872824
Thanx everyone for the time and attention.

No Windows Solution was provided.

I am using a sefl develop Linux Solution.
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