[NCLUG] A question about a web server and broadband.

[Michael Dwyer]

"J. Paul Reed" wrote:
> 
> On Wed, 20 Feb 2002, Sean Roberts wrote:
> 
> > Is it the DHCP server that would ping you?
> >
> > I try to keep my firewall rules pretty tight and that includes not
> > allowing anyone but a select couple of computers to ping me.  Should I
> > open up ping to my DHCP server too?
> 
> I should go read the RFC, but I was under the impression that the DHCP
> client kept renewing the lease, and if the client failed to so within the
> leasetime, then the server assumed it was expired... that is, the
> responsibility was on the client's head, not the server's.

I believe that the DHCP server sends an ICMP ping.  That way it is able
to also find devices that are not using DHCP.  Obviously, if the client
and server have a ... er... relationship? ... then the server doesn't
need to ping.  I believe that the ISC DHCPd will test a 'free' address
with a ping to make sure it is truly free.

That is, if the server thinks that the lease it expired, it will
normally still ping the address to make sure that some squatter isn't
sitting on the address.  These addresses are then marked unusable by the
DHCPd, and apparently can be somewhat of a problem when they stack up.

I understand that this is needed for BOOTP clients...  SOmething like
that.  Its been a while since I read the docs, too...