Behavior with clients using "Broadcast Flag"
dhcp at nryc.fr
Fri Oct 5 22:09:57 UTC 2012
I'm using dhcpd version 4.1.1 (Debian Squeeze) and I have some Windows
Seven clients doing some "discover" instead of "request". This is an
Sep 26 01:19:34 dhcpd: DHCPDISCOVER from 00:1c:c0:fc:f7:24 (VNDLOL65TEE)
Sep 26 01:19:34 dhcpd: ICMP Echo reply while lease 172.20.24.86 valid.
Sep 26 01:19:34 dhcpd: if VNDLOL65TEE.domain.com IN TXT
"31a956a7940aee9c9191f5c7770adf3ed5" rrset exists and
VNDLOL65TEE.domain.com IN A 172.20.24.86 rrset exists delete
VNDLOL65TEE.domain.com IN A 172.20.24.86: success.
Sep 26 01:19:34 dhcpd: if VNDLOL65TEE.domain.com IN A rrset doesn't
exist and VNDLOL65TEE.domain.com IN AAAA rrset doesn't exist delete
VNDLOL65TEE.domain.com IN TXT "31a956a7940aee9c9191f5c7770adf3ed5": success.
Sep 26 01:19:34 dhcpd: removed reverse map on 184.108.40.206.in-addr.arpa.
Sep 26 01:19:34 dhcpd: Abandoning IP address 172.20.24.86: pinged before
I think this behavior is caused by the DHCP "Broadcast flag" introduced
by default by windows Vista (to be confirmed) :
I'm trying to understand what's happening. The DHCP server :
- receives a "DHCPDISCOVER", assumes that the client has no IP address
but in fact the client is using its currently leased address (172.20.24.86).
- finds a previous lease with the client hardware address, associated
with the IP address 172.20.24.86
- sends an ICMP message to the IP address before replying to the client
- gets and ICMP response from the IP address and declares the lease
invalid, cleans the DNS
- assigns another IP address to the client (not displayed in the log).
Am I right?
Is there a workaround for this on the server-side, maybe on newer
versions of dhcpd?
Off topic : we've been playing with the registry settings to reproduce /
fix this problem and it's not working : the clients keep doing broadcast
whatever the settings are and we cannot force a "fresh" install to do
Any help on this would be appreciated, the tech support is blaming the
DHCP server :)
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