DHCP issue multiple IPs to one MAC address?

[BLJUNG]

We are implementing portable data terminals (PDTs) with 4-slot ethernet cradles under an NT4 SP6a workstation and Wingate 6.1.1. The cradles request and IP for themselves and IPs for each of their four cradle slots (5 total) using the same MAC address with an added extension (for each slot). The DHCP behaviour is confusing as it hands out an IP for the cradle (request 1) and a different IP for the first slot (request 2) but re-issues the second requests IP when is makes the request for the third slot.

Why would this occur.? If multiple IPs per MAC address are not supported by the DHCP server I would have expected the same IP on the second request, not the third.

Does the DHCP server support multiple IPs to a singel MAC address?
Does the DHCP server support MAC address extensions fo the above scenario?
If so, how can I invsitgate and or set the configuration?

[adrien]

Hi

Just looked through the code. WinGate DHCP service indexes clients by MAC address, so a subsequent request from the same MAC will be deemed the same client, and the previous IP would be assigned.

So not sure why it gives you a different IP on try 2, are you sure it's the same MAC?

Adrien

[BLJUNG]

Hi Adrien,

Thanks for the code investigation. Its helpful.

We will try to sniff the MAC addresses being passed with each request from the cradle and post back here. Cradle vendor has told us the cradle adds an extension to the MAC address to distinguish each slot it requests an IP for, but did not tell us the format or length of the address extension. Sniffer results should help with this. I guess this goes to my other question

"Does the DHCP server support MAC address extensions..."

The following suggests the MAC address extensions may be the issue.
When the cradle is connected directly to the main network (not via the PC and wingate) it obtains IPs with no problems from the main network's DHCP server. There are non-technical reasons for us NOT to use this setup, we tried it simply as a test.