Date: Tue, 28 Dec 1999 12:46:30 -0800 From: Shawn Ramsey <shawn@megadeth.org> To: freebsd-questions@FreeBSD.ORG, freebsd-questions@FreeBSD.ORG Subject: Re: arplookup Message-ID: <4.2.0.58.19991228124339.01ba7750@mail.cpl.net> In-Reply-To: <199912280203.DAA23875@dorifer.heim3.tu-clausthal.de>
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At 03:03 AM 12/28/99 +0100, Oliver Fromme wrote: >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. :-) Yes, that makes sense, and I think I found the problem, but not quite sure what is wrong yet. If I do a traceroute from this box to one of the local workstations, it goes out through the default route rather than directly to the machine. I guess a netmask is setup wrong somewhere, but I haven't found it. This particular BSD box is connected to many different networks, and about 120+ IPS assigned to it. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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