Date: Thu, 9 Aug 2001 13:13:52 -0400 From: Jonathan Chen <jon@FreeBSD.ORG> To: bv@wjv.com Cc: net@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: forwarding broadcast Message-ID: <20010809131352.A15148@enterprise.spock.org> In-Reply-To: <20010809125747.A33178@wjv.com>; from bill@wjv.com on Thu, Aug 09, 2001 at 12:57:47PM -0400 References: <20010809113638.A9519@enterprise.spock.org> <20010809122352.B32613@wjv.com> <20010809123056.G9519@enterprise.spock.org> <20010809125747.A33178@wjv.com>
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On Thu, Aug 09, 2001 at 12:57:47PM -0400, Bill Vermillion wrote: > On Thu, Aug 09, 2001 at 12:30:56PM -0400, Jonathan Chen thus sprach: > > On Thu, Aug 09, 2001 at 12:23:52PM -0400, Bill Vermillion wrote: > > > On Thu, Aug 09, 2001 at 11:36:38AM -0400, Jonathan Chen thus sprach: > > > > > > > On FreeBSD -CURRENT and -STABLE, packets to broadcast addresses > > > > are not forwarded. For instance, if I have a FreeBSD router with > > > > interfaces 192.168.1.1 and 192.168.2.1, and I send packets from > > > > 192.168.1.2 to 192.168.2.255, the packets are dropped to the > > > > floor. IMO, this is wrong... > > > > But the question now is - what is the netmask on these interfaces.? > > > That will make a difference. > > > These are both class C networks, and their netmask is specified > > accordingly (/24). I'm pretty sure my setup is correct here. > > So they are two separate networks therefore a broadcast for one > should not go the other. > > If on the other hand you netmask was 255.255.252.0 then > 192.168.0.x thru 192.168.3.255 would be part of the same network > and you'd expect a broadcast to propagate. At least this is how I > understand how it works, and I could be wrong. I think you are misundering the setup here. In plain english and without the use of confusing IP/netmasks: A machine connected to interface 0 of the router is sending a unicast ethernet packet (directed to interface 0 of the router) to the ip broadcast address of interface 1. It used to be that routers were expected to go ahead and broadcast the same ip packet on network 1, but a recently updated standard changed the requirements so it is no longer true. Of course, broadcasts from a machine on interface 0 to the ip broadcast address of network 0 is not expected to appear on network 1... -Jon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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