From owner-freebsd-net@FreeBSD.ORG Tue Feb 12 18:28:12 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id CE8EAA9D for ; Tue, 12 Feb 2013 18:28:12 +0000 (UTC) (envelope-from scott4long@yahoo.com) Received: from nm23-vm1.bullet.mail.ne1.yahoo.com (nm23-vm1.bullet.mail.ne1.yahoo.com [98.138.91.50]) by mx1.freebsd.org (Postfix) with ESMTP id 8452C926 for ; Tue, 12 Feb 2013 18:28:12 +0000 (UTC) Received: from [98.138.226.177] by nm23.bullet.mail.ne1.yahoo.com with NNFMP; 12 Feb 2013 18:28:05 -0000 Received: from [98.138.84.40] by tm12.bullet.mail.ne1.yahoo.com with NNFMP; 12 Feb 2013 18:28:05 -0000 Received: from [127.0.0.1] by smtp108.mail.ne1.yahoo.com with NNFMP; 12 Feb 2013 18:28:05 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1360693685; bh=hblbWX95sR1EnoBTTkhr566grT7IA/S2GN8BuTSkt+0=; h=X-Yahoo-Newman-Id:X-Yahoo-Newman-Property:X-YMail-OSG:X-Yahoo-SMTP:Received:Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc:Content-Transfer-Encoding:Message-Id:References:To:X-Mailer; b=tlRuLcjJi/Mws8Xqeh1nFCEB6derxEPuLYvp4c3l9yqzzXRQV/rVvMhPbCa3LgHlDafx4ML0/5Q6+erVc4uXTOeHysx7+gOjlQdz3mzuoZk+4ayWeYGSTnDBeXd4JVC59JTftO+w4z2n4ryZ8alnlTQSgjqakmEzpDMCf1YTwPs= X-Yahoo-Newman-Id: 253025.38486.bm@smtp108.mail.ne1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: X8wL7BIVM1lmSxVvGKTSx8s3sk6__j30hbEmThsS2sIYzo6 jkEg4jivdFIXybXyVFkbiDuNOzuvfoPPy_A_Aad897Tt2mm8p6JOKKC2i3uR _0zi7tgglmoKwwGxx96omxL3weM4bdhGCq_fsXC9I.bm1XtalmRoEFBvdQ9v hCpey9vkddd2clCCsiCBT8hX10w20XddR10hq3AfHYjmL7l12VCEAAabrKlk t_we627x8sfZt7gqPSnn_mOlwMGa2NBZ.SsX5DW8n43Hra61.nH6Te.YrQkf XYV.Dz_p7m3FhgLjvlyOTSurc.SED2U.C4vz9wM9Ih2aQ72v21G3Eh2mZsT_ FVnKi818TJPpgW9_L7CjnUWRKYGTpHDXARROvrRAfpldM_eYwzugaDpjIDq5 .uU4fldhbmxvT1M5ATzhdlW8OOB_jeB_9_aQkF5z1G2RdLNuhATg4Z5XIVfH ygyne8_wYGRLA X-Yahoo-SMTP: clhABp.swBB7fs.LwIJpv3jkWgo2NU8- Received: from [10.64.24.202] (scott4long@69.53.237.126 with plain) by smtp108.mail.ne1.yahoo.com with SMTP; 12 Feb 2013 10:28:05 -0800 PST Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 6.2 \(1499\)) Subject: Re: Problems with two interfaces on the same subnet? From: Scott Long In-Reply-To: Date: Tue, 12 Feb 2013 11:28:04 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: References: To: Ivan Voras X-Mailer: Apple Mail (2.1499) Cc: freebsd-net@freebsd.org X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Feb 2013 18:28:12 -0000 On Feb 12, 2013, at 11:06 AM, Ivan Voras wrote: > On 12/02/2013 18:57, Ivan Voras wrote: >> On 12/02/2013 18:52, Freddie Cash wrote: >>> Any reason you can't just use lagg(4) in one of the non-LACP modes? = That's >>> bascially designed to do exactly what you want. >>=20 >> No particular reason, I'm just not familiar enough with it. Will e.g. >> the "loadbalance" mode "just work" ? Should I expect any problems? >=20 > Actually, I know next to nothing about link aggregation. How do ARP > requests get solved? Would an attached L3-aware switch see the same IP > address on two ports? Since "loadbalance" chooses ports based on a = hash, > it will probably start dropping 50% of the outgoing traffic if one of > the two links dies? >=20 >=20 If you use simple load balancing, either via round-robin or hashed = flows, then yes, your switch will see 2 MAC addresses and a single IP. I believe = that in this scheme only one interface will respond to ARP requests, so peer hosts = won't get too confused, and if your switch is only capable of L2, everything will = work ok for transmit. I'm less clear on receive; maybe some L2 switches are smart = enough to detect this situation and balance incoming traffic, otherwise I can't = see how RX traffic to a single MAC could be split to other MACs. If your switch is L3 aware, then yes, the simple load balancing will = confuse it. However, if it's L3 aware then it's likely going to implement = standardize channel bonding, either in the form of legacy Etherchannel/FEC or more modern = LACP/802.3ad. LACP isn't perfect, and it's quite easy for links to physically be up = but logically be down, resulting in blackholed traffic, but it's better than FEC. I have = patched to made the FreeBSD LAGG/LACP code a little more reliable in this area, and I'll = be posting those patching in the coming few days. Scott