relay - discover interfaces.
foomail123 at yahoo.com
Fri Aug 11 17:58:25 UTC 2006
Thank you for informative email.
--- Glenn Satchell <Glenn.Satchell at uniq.com.au> wrote:
> >Date: Thu, 10 Aug 2006 15:50:25 -0700 (PDT)
> >From: foomail123 <foomail123 at yahoo.com>
> >Subject: relay - discover interfaces.
> >To: dhcp-users at isc.org
> >Does relay always expect interfaces to be up
> >before relay is run ?
> >Is there a way for relay to smartly detect
> It does - sort of. The algorithm is to get all
> interfaces that are up,
> then remove loopback, any non-broadcast interface
> types, and point to
> point, then use whatever is left. If you specify any
> interfaces on the
> command line then it starts with those and goes
> through the same
> elimination process. See the discover_interfaces()
> function in
> common/discover.c in the source distribution.
> >When interfaces go down or change IP address, how
> >does relay get notified ?
> System dependant. In linux you can use the
> ifup/ifdown scripts to
> restart dhcrelay. Restarting is ok as dhcrelay does
> not store any state
> and usually starts very quickly. Mostly though it
> probably doesn't get
> It doesn't make much sense for dhcrelay to use
> unconfigured interfaces,
> since it needs the IP address assigned to that
> interface so that it can
> add it to the packet it is forwarding to the dhcp
> server. If the
> interface is not up then the IP address either isn't
> assigned yet, or
> it could change as it is brought up.
> If you have interfaces going up and down on your
> dhcp server you may
> want to rethink your network design, and come up
> with a way for the
> interfaces to always be up. Perhaps a small switch
> or hub on some of
> the interfaces would allow them to always be up?
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