Date: Tue, 28 Dec 1999 03:03:58 +0100 (CET) From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de> To: freebsd-questions@FreeBSD.ORG Subject: Re: arplookup Message-ID: <199912280203.DAA23875@dorifer.heim3.tu-clausthal.de>
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Shawn Ramsey wrote in list.freebsd-questions:
> arplookup 192.216.87.246 failed: host is not on local network
>
> Does anyone know what that error means, and how I might fix it? I am
> getting these sorts of entries on the console for numerous(maybe all) of
> the workstations on that network.
It most probably means that the host with the IP number
192.216.87.246 has a wrong netmask configured.
For example, assume that two hosts A and B are on two different
class-C networks, i.e. their "natural" netmask is 255.255.255.0.
Then assume that host B has a (wrong) netmask configured which
is 255.255.0.0, but it still can reach A because there's a
switch or a bridge between them (or something similar) which
just forwards the packets.
Now when B sends a packet directly to A (without using the
default route, because of the wrong netmask), A will add B to
its arp table. This normally happens every time the IP stack
discovers a "new" host on the network, to save ARP requests.
However, the kernel will discover that B is not on its local
network (according to the correct netmask), therefore the arp
entry is not valid (hosts which are on other networks are
only reachable through the default route [or some other route],
but not directly, so they cannot have their own arp entries in
the arp table of A).
This is clearly an error, and so your syslog entry is
generated.
To fix it, you should correct the netmasks of those hosts.
I hope my explanations make some sense to you. :-)
Regards
Oliver
--
Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany
(Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de)
"In jedem Stück Kohle wartet ein Diamant auf seine Geburt"
(Terry Pratchett)
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