Date: Tue, 12 Aug 2008 08:50:16 -0700 From: Andrew Thompson <thompsa@FreeBSD.org> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: stable@freebsd.org, Eugene Grosbein <eugen@kuzbass.ru>, Marian Hettwer <mh@kernel32.de> Subject: Re: lagg(4) and failover Message-ID: <20080812155016.GB45850@citylink.fud.org.nz> In-Reply-To: <20080812112430.GC64458@server.vk2pj.dyndns.org> References: <a588673badeccac53d23f7964c216f62@localhost> <20080812105552.GA89695@svzserv.kemerovo.su> <20080812112430.GC64458@server.vk2pj.dyndns.org>
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On Tue, Aug 12, 2008 at 09:24:30PM +1000, Peter Jeremy wrote: > On 2008-Aug-12 18:55:52 +0800, Eugene Grosbein <eugen@kuzbass.ru> wrote: > >On Tue, Aug 12, 2008 at 12:37:15PM +0200, Marian Hettwer wrote: > > > >> I'm using lagg(4) on some of our servers and I'm just wondering how the > >> failover is implemented. > > As far as I can tell, not especially well :-(. It doesn't seem to detect > much short of layer 1 failure. In particular, shutting down the switch > port will not trigger a failover. > > >> The manpage isn't quite clear: > >> > >> failover Sends and receives traffic only through the master port. > >> If > >> the master port becomes unavailable, the next active port > >> is > >> used. The first interface added is the master port; any > >> interfaces added after that are used as failover devices. > >> > >> What is meant by "becomes unavailable"? Is it just the physical link which > >> needs to become unavailable to trigger a failover? > > It seems to be, > > >Yes. It seems you need lacp protocol described later in the manual. > > Actually, lacp and failover are used differently: lacp is primarily > used to increase the bandwidth between the host and the switch whilst > failover is used for redundancy. > > With lacp, all the physical interfaces must be connected to a single > switch. With failover, the physical interfaces will normally be > connected to different switches (so a failure in one switch will not > cause the loss of all connectivity. Actually you can use lacp in failover mode by connecting interfaces to different switches. It will only bundle an aggregation to one switch at a time but if that becomes unavailable then it will automatically choose the next switch. Andrew
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