DHCPNAK reply using wrong server identifier IP

Vic Berdin vic at digi.ph
Thu May 26 06:49:05 UTC 2011

Hi ISC-DHCP-Users,

I have configured dhcpd.conf to use an global 'option dhcp-server-identifier
xxx.xxx.xxx.xxx' directive since my server box has more than one IP (raised
on an alias device). This 'dhcp-server-identifier IP' is actually an alias
IP via eth0:0. 

Now, after playing with Wire Shark, I noticed that each time the server
issues a DHCPNAK reply (due to a client DHCPREQUEST for a wrong IP), the
DHCPNAK is being sent thru the real IP in eth0, and not thru the configured
'option dhcp-server-identifier IP' eth0:0 IP.

My questions now are:

1. Is there a specific reason why DHCPNAK replies do not follow the global
'option dhcp-server-identifier xxx.xxx.xxx.xxx' directive? 
2. Should I use a 'server-identifier IP' sub-directive ('tho I haven't tried
yet) instead of a global one? 

Any tips/explanations are very much welcome.

Best regards,

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