2003 DHCP option 82

[digiteck7]

I couldn't find anything on DHCP option 82 support in windows 2003.

I was wondering if:

a) anyone knows if its there or not

b) if there is a way to some how add it myself

c) get some type of plugin

I do not manage servers, just networks, and would like to have option 82 enabled on DHCP service so i can see the switch and port associated with the IP without searching all over. Since I don't know much about the DHCP service, or adding options, I was wondering if anyone knew anything or could point me in the right direction.

[Apolyon]

I'm not an expert, so excuse me if this is not true...

The 82 option must be enabled on a switch, not on a windows server. That option allows the switch to identify the hosts on its own ports, so the switch sends info about itself and the port assigned to the client.

I'm sure that you could find more info on cisco...

I hope this helps :)

[dougkinzinger]

I believe that's right...it's switch-level.

[Eversurf]

Yeah its part of the switch configuration and it works with DHCP relay for Cisco and UDP helper for other switchs

Here is an Article that explain some of it. I had to look it up because i didn't know anything about it.

Correct me if i'm wrong and confirm it if i'm right but basically this feature enable you to create Virtual Vlan for each host connected to the switch???

Have fun!!!

[digiteck7]

I know this must be enabled on the switch, but the DHCP server needs to understand the option 82 part of the packet. I already know the switch needs to be configured, but when the DHCP packet comes to the DHCP server, it needs to be able to strip off, interpret, and add the option 82 info.

It's stated in the first paragraph of the link you posted: This feature enables the DHCP relay agent (Catalyst 3550 switch) to include information about itself and the attached client when forwarding DHCP requests from a DHCP client to a DHCP server.

Option 82 must be configured on switch AND the DHCP server. I'm looking to set it up on the server.

[Apolyon]

Well, you can right click on the server on your DHCP mmc, and go to "Set Predefined Options..." and add it manually, but I don't know what to add... lol

[Eversurf]

I have checked on my DHCP server this morning and there is nothing related to Options 82 anywhere.

Makes me wonder...

[ranger24]

Option 82 & Windows Servers -Grrrrrrrrr

Option 82 is used by DHCP relay agents to allow them to keep track of DHCP requests and deal with them more effectively.

WHAT SHOULD HAPPEN:

1)"DHCP Discover" packet broadcasted into network.

2)DHCP relay agent (Switch, DSLAM, Router, etc) sees the DHCP broadcast, and modifies it:

a) Adds its IP address in the <source address> field

b) Adds DHCP server address in the <destination address> field

c) Add option82 to the end of the packet containing details of where the broadcast came from (which interface, original source mac etc)

(at this stage the broadcast packet is now a unicast packet thus saving network resources)

3) Packet is then sent to server who should respond with a DHCP OFFER packet containing details of its service (IP address available, lease time etc) and OPTION 82 should e returned UNCHANGED. DHCP servers are not supposed to touch this option, just return it!

4) Relay agent recieves DHCP OFFER and can forward it as unicast packet straight to the PC that sent it based on the info in OPTION 82.

Without OPTION 82 then the packet would be broadcast on the same interface the DHCP relay agent recieved it on.

Hope that is clear....

And so far I have not found away of implementing this in windows. It just doesn't support it. It is possible to add new options - however I can't find a mechanism to tell the server to return option 82 untouched if it recieves it...

Good luck