Hostname differences between servers

[Norman Elton]

Eugene -

Thanks for the tip, I didn't see your response until just now. I did
do a packet capture, and caught one of these "in the wild". The
packets coming into dhcpd are consistently using one hostname, but the
two servers are logging two different hostnames. In the previous
example, for instance, the packets would show Michaels-iPhone, but one
of the servers is erroneously logging android-9375f90cad51e32f.

Thanks!

Norman
On Tue, Oct 2, 2018 at 1:59 PM Eugene Grosbein <eugen at grosbein.net> wrote:
>
> 02.10.2018 21:53, Norman Elton wrote:
>
> > In our environment, we have multiple routers (VRRP) forwarding
> > requests to two DHCP servers, run in failover. So if a client
> > broadcasts out a DHCPREQUEST, that message is handled multiple times.
> > Not a big deal, it's been working great for years.
> >
> > We've just noticed that, sometimes, the hostname reported by the two
> > servers don't match each other. For instance:
> >
> > Oct  1 01:03:48 landlord01: DHCPREQUEST for 10.45.13.196
> > (128.239.10.121) from e8802ea2eb7f (Michaels-iPhone) via 10.45.13.2
> > Oct  1 01:03:48 landlord02: DHCPREQUEST for 10.45.13.196
> > (128.239.10.121) from e8802ea2eb7f (android-9375f90cad51e32f) via
> > 10.45.13.2: lease owned by peer
> >
> > So, is it an android, or is it an iPhone? In this case, the mac
> > address points to Apple, but why is one server reporting the hostname
> > is android-9375f90cad51e32f?
> >
> > This is happening fairly frequently. Our servers are running the
> > RHEL-provided version of ISC dhcpd, 4.1.1-61.P1.el6_10.
> >
> > Any ideas?
>
> First, you should use tcpdump -enpvvvs0 to see more details of requests
> and look for differences as they have much more parts than dhcp servers shows.
>
> You may be having un- or mis-configured dhcp relay/proxy in the network duplicating requests.
>