ISC dhcpd ignoring DHCP discover

Johannes Bauer dfnsonfsduifb at
Wed Jan 9 13:29:05 UTC 2013

Hi list,

I'm currently implementing a DHCP client on a small embedded system.
It's plugged into my local home network which is served DHCP by the
isc-dhcpd. The embedded system tries to DHCP DISCOVER, but the server
just ignores the packet.

That is, it doesn't even log the DISCOVER or display anything, but just
silently drops it. I've verified with tcpdump that the discover actually
makes it the the isc-dhcpd.

I really don't know what could be wrong. Option fields I include in the
request are

- MsgType (DISCOVER)
- Vendor class identifier
- Parameter Request list
  * Subnet mask
  * Router
  * DNS
  * Broadcast addr
  * IP lease time
  * DHCP server identifier
- End

Here's a 360 Byte pcap of that single ignored and lonely packet:

Maybe I'm missing something really obvious here, but I can't see it.
Could you please help me find out why isc-dhcp ignores that packet?

Thanks in advance,

More information about the dhcp-users mailing list