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(DHCP) I don't receive REQUEST packet

asked 2018-07-26 14:03:26 +0000

SteMMo gravatar image

updated 2018-07-26 14:07:34 +0000

Hello everyone,
I'm writing a simple DHCP server for a ARM microprocessor.
I directly connected it with a Win PC by an Ethernet cable: the PC acts as a DHCP client.
After some seconds I receive (4!) DISCOVER packet(s).
I reply with OFFER packet where I send an IP.
The server has IP =
It is offering the IP =

This is the Wireshark dump:

Image @ Dump

Why the client is not requesting the REQUEST packet?


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Troubleshooting via screen shot is usually an exercise in frustration because the item we want to see isn't shown. Can you upload the capture file to a public share, e.g. Cloudshark, Google Drive, DropBox etc. and amend your question with a link to the capture file?

grahamb gravatar imagegrahamb ( 2018-07-26 14:19:54 +0000 )edit
SteMMo gravatar imageSteMMo ( 2018-07-26 14:28:40 +0000 )edit

Maybe it is cause the OFFER has destination = broadcast instead of the new IP? Is it yet active?

SteMMo gravatar imageSteMMo ( 2018-07-26 14:36:27 +0000 )edit

Better .. it is missing the destination MAC address (broadcast now..), is it?

SteMMo gravatar imageSteMMo ( 2018-07-26 16:01:26 +0000 )edit

This capture is not from a DHCP server on an ARM processor, unless Dell is making those. Also the client MAC address in the OFFER is wrong, and there are funny trailing bytes.

Jaap gravatar imageJaap ( 2018-07-26 16:07:54 +0000 )edit

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answered 2018-07-27 04:47:14 +0000

Jaap gravatar image

The OFFER contains a field called Client MAC address. This is for the client to match DISCOVERS with OFFERS (among other things). In the OFFER this field is filled with the MAC address of the Server, while it has to be the MAC address of the Client the OFFER is intended for.

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I confirm that the network broadcast is not a problem. Once corrected the Client MAC address field, the process is OK. Thanks

SteMMo gravatar imageSteMMo ( 2018-07-27 09:17:39 +0000 )edit

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Asked: 2018-07-26 14:03:26 +0000

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Last updated: Jul 27 '18