From owner-freebsd-questions@FreeBSD.ORG Fri Jun 24 10:49:44 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4E2C416A41C for ; Fri, 24 Jun 2005 10:49:44 +0000 (GMT) (envelope-from sineathj1@citadel.edu) Received: from imf20aec.mail.bellsouth.net (imf20aec.mail.bellsouth.net [205.152.59.68]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0B87643D48 for ; Fri, 24 Jun 2005 10:49:43 +0000 (GMT) (envelope-from sineathj1@citadel.edu) Received: from ibm62aec.bellsouth.net ([65.12.54.138]) by imf20aec.mail.bellsouth.net with ESMTP id <20050624104943.PRCF1983.imf20aec.mail.bellsouth.net@ibm62aec.bellsouth.net> for ; Fri, 24 Jun 2005 06:49:43 -0400 Received: from GARUDA ([65.12.54.138]) by ibm62aec.bellsouth.net with SMTP id <20050624104942.XIMG8050.ibm62aec.bellsouth.net@GARUDA>; Fri, 24 Jun 2005 06:49:42 -0400 Message-ID: <000501c578aa$6d5cf830$0463a8c0@GARUDA> From: "James Bowman Sineath, III" To: "Ulf Magnusson" , References: <5675255661ae.5661ae567525@liu.se> Date: Fri, 24 Jun 2005 06:49:42 -0400 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2527 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2527 Cc: Subject: Re: NAT router confusion X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 24 Jun 2005 10:49:44 -0000 My understanding is that the netmask (255.255.255.0 as you put it) is only to determine how much of the IP address is used for the subnet address. I'm a newb with this as well, so please, someone correct me if i'm wrong. If your IP is 192.168.1.10 and your netmask is 255.255.255.0, then only the last 8 bits of your IP (the last .10) is usable for a specific host on the network and the first 24 bits are used for the network address and subnet address. In binary: 11111111.11111111.11111111.00000000 would be your netmask and only the trailing 0's can be used for a host address. This could also be expressed as 192.168.1.0/24 using CIDR. Let me try to give you another example: if your IP range was 192.168.99.0 to 192.168.99.255 and netmask was 255.255.255.254 then, in binary, the netmask would look like this: 1111111.11111111.11111111.11100000 Being that you are using 192.168.99.0 as the network address, the first three 1's in the last 8 bits of the netmask would be your subnet addresses. So you could use.192.168.99.32, *.64, *.96, *.128, *.160 and *.192 for subnet addresses and the IPs between all of those (except the last IP, so you can only assign 30 per subnet since the last IP is used for broadcast) can be assigned to hosts. Hopefully that (correctly) clears up any confusion involving subnets and netmasks. Like I said, I'm new at as well, so please correct me if I am wrong. ----- Original Message ----- From: "Ulf Magnusson" To: Sent: Friday, June 24, 2005 6:25 AM Subject: Re: NAT router confusion > ----- Original Message ----- > From: "Michael H. Semcheski" > Date: Friday, June 24, 2005 1:46 am > Subject: Re: NAT router confusion >> On Thursday 23 June 2005 07:43 pm, Ulf Magnusson wrote: >> > Is this router really some switch/router hybrid? Or..? Bleh, someone >> > please sort this out for me. I realize this isn't strictly >> > FreeBSD-related, but I simply couldn't think of a better place to >> pick> brains, so I hope I'll be excused :) >> >> It is a switch / router hybrid. If the traffic is going to an >> address on the >> same network, its a switch. If the traffic is going to an address >> on a >> different network, its a router. >> >> If you understand that concept, then you should have a pretty good >> idea of how >> the system works. >> >> I do not have a complete enough understanding of IP networks to >> explain this >> in specific detail. I think the key is that the computer >> generating the >> traffic looks at the netmask for the sending interface (eg, >> 255.255.255.0) >> and uses this to determine if the endpoint of the traffic is on the >> same >> network or not. If it is, it sends the traffic directly to the >> host. If it >> is on a different network, it forwards the traffic to the gateway >> address. >> Mike > > Thanks, I think I understand how it works now. I guess it's basically > like an ordinary router that pretends it's a switch for all addresses > that appear on the same local network. It looks at the destination > address in IP packets and the address of the sending system and goes > into switch mode if they both appear on the same subnet (which is pretty > much verbatim what you said, when I think about it). > > I'll throw another short question in the mix while I'm at it.. perhaps I > should rename the thread "Switching/routing questions from a curious > networking newbie" :-) > Do switches gain anything by having full-duplex connections to hubs? I > understand there must be a performance benefit when you connect a host > directly to a switch, but won't the half-duplex connections of the hosts > to the hub become a bottleneck? > > Ulf > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "freebsd-questions-unsubscribe@freebsd.org"