Date: Mon, 21 Aug 2000 22:11:53 -0700 From: "Crist J . Clark" <cjclark@reflexnet.net> To: "Larry Skarpness Jr." <larry@chainsoft.com> Cc: Janko van Roosmalen <janko@compuserve.com>, freebsd-questions@FreeBSD.ORG Subject: Re: ARP issues with 2 or more multi-homed interfaces on same physical LAN Message-ID: <20000821221153.E28027@149.211.6.64.reflexcom.com> In-Reply-To: <004a01c00be8$9cdc5ee0$0a00a8c0@chainsoft.com>; from larry@chainsoft.com on Mon, Aug 21, 2000 at 08:25:25PM -0700 References: <Pine.BSF.4.10.10008220246190.2305-100000@parmenides.utp.net> <004a01c00be8$9cdc5ee0$0a00a8c0@chainsoft.com>
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On Mon, Aug 21, 2000 at 08:25:25PM -0700, Larry Skarpness Jr. wrote: > Janko, > > Thanks for the quick response. Allow me to clarify the situation. The NICs > have different IPs, different networks, and differenct ethernet addresses. > They just happen to be connected to the same network hub. Obviously this is > a somewhat unusual configuration. The OS detects this situation as it > should, however it spews warning messages constantly when just one would be > enough. > > Some might be asking why would you want to do this in the first > place. You bet. > I am > situtuated on a cable modem. The ISP has supplied two completely different > IPs and different networks through this one cable modem. The ISP severly > limits the upload bandwidth, even between IPs on networks within their > control. So I have also multi-homed these two machines to another private > local network on which other machines exist. Oh no. > NAT is also being used on one > of the public IPs to support other machines on the private network. All of > these machines and the cable modem are wired into the same network hub, as > there is no reason to physically seperate them. Yes there is. > Through this mechanism all > the machines can reach eachother on the private net, and get out to the > internet. > > Machine 1 has > NICA HUB1 > IPA NETA (cable modem1) supports NAT to outside > NICB HUB1 > IPB NETB (local1) > Machine 2 has > NICC HUB1 > IPC NETC (cable modem1) > IPD NETB > Machine 3 has > NICD HUB1 > IPE NETB > Cable mdem 1 on HUB1 > > I think this is a valid configuration. A couple bad things. You are mostly likely leaking all of your "private" traffic over your cable modem. If you are running a firewall, no bother since it isn't protecting anything but the host it is running on. > Machine 1 complains that ARPs on > NICA are picked up on NICB, which in this situation would be expected. Is > there some reason why the FreeBSD OS must be so noisy about it? I WANT two > or more NICs in the same machine on the same physical network. Can I ask why? All it can do is hurt your local throughput. > The hack I > made to if_ether.c forces the OS quiet about it. Others are in the same > situation and would probably like this option without the neccessity to > hack. If you get this error, it's because you have multiple NICs from one host connected to a collision domain. There is no reason to do this, like I said, it hurts your network capacity. You are better off with one NIC and putting multiple IPs on the one NIC. -- Crist J. Clark cjclark@alum.mit.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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