DHCPDISCOVER packets being received by host, but not responded toby dhcpd

CARTWRIGHT, CORY C (ATTSNET) cc3283 at att.com
Wed Jun 10 11:36:05 UTC 2009

Hi Kyle,

I ran into this same symptom but the cause is probably not the same.  I
recently had an issue with 2-wire home gateways in which they broadcast
on vlan 0.  According to 802.1q vlan 0 is not a valid vlan but rather a
"null" used to supply packet with a priority.  Both Linux and Cisco
2960, not the 2950's would not respond to the packets from the 2-wire.
I was able to create a vlan 0 on my Linux and all worked.  I am still
working on the Cisco switch.  I am trying to avoid having to configure
each and every 2-wire device.

Hope this helps,

-----Original Message-----
From: dhcp-users-bounces at lists.isc.org
[mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of Kyle Dion
Sent: Thursday, June 04, 2009 4:44 PM
To: dhcp-users at lists.isc.org
Subject: DHCPDISCOVER packets being received by host, but not responded
toby dhcpd

Hi all,
This is kind of an off the wall question, and I'm not sure if this is 
the right place to ask it.  If this is not the right forum, then I 
apologize in advance.  I am running a pair of ISC DHCP 4.0.1 servers, 
with failover, on RHEL4 (32-bit).  Generally, this setup works 
flawlessly.  However, I have run into a situation recently, where a 
small number of clients are sending DHCPDISCOVER packets to the servers,

and I have been able to confirm with packet captures on the server, that

the host is receiving them.  However, the logs never show that dhcpd 
received or recognized the DHCPDISCOVERs.  Also, maybe not surprisingly,

the server-side packet captures show that the server never responds with

a DHCPOFFER (or any other message).  The DHCPDISCOVER packets AFAICT 
with Wireshark *are* valid, so I am at a loss.  Any light that could be 
shed on this or any guidance as to further troubleshooting steps or a 
better place to escalate this would be greatly appreciated.


Kyle Dion
Technical Operations
VMware, Inc.
kdion at vmware.com
dhcp-users mailing list
dhcp-users at lists.isc.org

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