Subject: Re: dhcpd(8) _cannot_ be completely disabled on an interface
To: , <>
From: David Laight <>
List: tech-net
Date: 01/07/2002 10:19:54
> The problem is, unlike the other udp ports which dhcpd(8) uses (67,
> 111), dhcpd does _not_ listen on port 68.  It appears that it is using
> bpf to snatch packets directly from the wire.  As bpf does (and should)
> get a shot at packets before ipf does its magic, this port is de facto
> open regardless of ipfilter rules stating otherwise (test this.  no
> really.  run dhcpd on a host, block all udp packets to port 68, and nmap
> - -sU scan the host.  you may be surprised).
> And yes, this occurs even though dhcpd(8) is explicitly _not_ started on
> the outside interface.
> To review:
> Inside interfaces are ray0 and le0 (yes, dhcp is limited to a specific
> set of hardware addresses on ray0.  that's another discussion).  Outside
> interface is vr0.
> from rc.conf:
> ...
> ipfilter=YES                                    # uses /etc/ipf.conf
> ipnat=YES                                       # uses /etc/ipnat.conf
> ...
> dhcpd=YES               dhcpd_flags="-q le0 ray0"
> ...

What happens if you start dhcpd after bringing up ray0 and le0 but
before bringing up vr0?
(doing this is left as an exercise...)