Using virtual interface with dhcpd v3.0.5

sthaug at sthaug at
Wed Aug 18 08:39:29 UTC 2010

> >This morning we copied the conf and lease files and started the 
> >server on the new machine.  It was processing DHCPDISCOVER requests 
> >on our eth1 interface, but not on the virtual eth1:1 interface. 
> >Both interfaces were processing DHCPREQUESTs.
> >
> >Any thoughts on what we need to do to get this working again?
> >
> >Also, can I put "eth1 eth1:1" on the startup command line, or is 
> >"eth1" sufficient?
> You can't use virtual interfaces with DHCP. Think about it, when a 
> broadcast packet comes in, how you you figure which interface it 
> should have been destined for ?

Actually you can, *if* your dhcpd is compiled with USE_SOCKETS and
you configure it to listen to a specific interface/IP address instead
of all broadcast traffic. It assumes all your requests are coming in
via DHCP relay agents (thus no broadcast handling needed). Obviously
this is not a general purpose DHCP installation, and you need to know
what you're doing...

Steinar Haug, Nethelp consulting, sthaug at

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