From owner-freebsd-questions@FreeBSD.ORG Fri Nov 15 15:19:53 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id C633FD1C for ; Fri, 15 Nov 2013 15:19:53 +0000 (UTC) Received: from bs1.fjl.org.uk (bs1.fjl.org.uk [84.45.41.196]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 5A0332FED for ; Fri, 15 Nov 2013 15:19:52 +0000 (UTC) Received: from [192.168.1.35] (host86-164-139-120.range86-164.btcentralplus.com [86.164.139.120]) (authenticated bits=0) by bs1.fjl.org.uk (8.14.4/8.14.4) with ESMTP id rAFFJjAg098935 (version=TLSv1/SSLv3 cipher=DHE-DSS-CAMELLIA256-SHA bits=256 verify=NO) for ; Fri, 15 Nov 2013 15:19:45 GMT (envelope-from frank2@fjl.co.uk) Message-ID: <52863B93.5030903@fjl.co.uk> Date: Fri, 15 Nov 2013 15:19:47 +0000 From: Frank Leonhardt User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: freebsd-questions@freebsd.org Subject: Re: lagg(4) question References: <201311151449.HAA04566@mail.lariat.net> In-Reply-To: <201311151449.HAA04566@mail.lariat.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.16 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Nov 2013 15:19:53 -0000 On 15/11/2013 14:49, Brett Glass wrote: > I'm interested in using lagg(4) to provide failover from a main > wireless link to a backup link. Unfortunately, one of the common > failure modes, when a link fails, is for the Ethernet port on the > radio to stay up but not pass any traffic. Does lagg(4) test the link, > by actually trying to send packets, to determine if the link has > failed? Or does it rely upon the Ethernet link losing "carrier"? > > --Brett Glass I'm pretty sure you're right. lagg (aka truck) determines if an interface is working by checking its "up" flag in the link_state flags field; it also checks the firewall's idea. I stand to be corrected, but I think it's only the interface driver's responsibility to check for a carrier, not to "down" itself it's its not getting data through when the hardware layer looks healthy. If we're right in our assumption, you could always have a cron job ping through the main wireless link, and if it fails to get a response you could fail it (down it with ifconfig), triggering lagg. Or you could just as easily ignore lagg and reconfigure the interfaces yourself. Regards, Frank.