Date: Sun, 9 Dec 2001 13:48:32 -0700 (MST) From: "Forrest W. Christian" <forrestc@imach.com> To: Jim Weeks <jim@siteplus.net> Cc: Rowan Crowe <rowan@sensation.net.au>, freebsd-isp@FreeBSD.ORG Subject: Re: arplookup Message-ID: <Pine.BSF.4.21.0112091340490.8824-100000@workhorse.iMach.com> In-Reply-To: <Pine.BSF.4.21.0112091132410.331-100000@veager.jwweeks.com>
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On Sun, 9 Dec 2001, Jim Weeks wrote: > Full circle indeed! This brings us back to the original problem, why > aren't these requests coming through the gateway in the first place. I > haven't had a strait answer to that question yet. Any enlightenment would > be appreciated. I'm going to put my $0.02 in here. Let's say you have two nets, call them a and b. We'll say they're subnets of the same "classful c" such as: 192.168.1.64-127 and 192.168.1.128-191. Note these are both 255.255.255.192 subnets. Let's say you have a router which is connected to both subnet a and b, with an address of 192.168.1.65 and 192.168.1.129 for each subnet respectively. The proper configuration would be to set up the hosts on each subnet with an address from that subnet, and set the default router/gateway to the respective router ip, and a netmask of 255.255.255.192. Each host should be able to get to every other host, regardless of the subnet, if this is set up correctly. Now lets assume you have a FreeBSD host on subnet a, which has an ip address of 192.168.1.100 and has a misconfigured netmask of 255.255.255.0. What is going to happen is that it will be able to reach everything on it's subnet, but not those of subnet b. When it tries to reach a host on subnet b, it will look at the address, say 192.168.1.150, and then see if it is in the same subnet as the freebsd box. Since net netmask is 255.255.255.0, it thinks that all of 192.168.1.x is in it's subnet, and as a result, starts sending out arp packets asking for the MAC address of 192.168.1.150. Since .150 isn't on the same wire, NOTHING RESPONDS (unless the router is kind enough to do proxy arp - which it shouldn't do). And then you get the errors you were seeing. - Forrest W. Christian (forrestc@imach.com) AC7DE ---------------------------------------------------------------------- The Innovation Machine Ltd. P.O. Box 5749 http://www.imach.com/ Helena, MT 59604 Home of PacketFlux Technogies and BackupDNS.com (406)-442-6648 ---------------------------------------------------------------------- Protect your personal freedoms - visit http://www.lp.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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