lagg(4) and failover
Peter Jeremy
peterjeremy at optushome.com.au
Tue Aug 12 11:24:41 UTC 2008
On 2008-Aug-12 18:55:52 +0800, Eugene Grosbein <eugen at 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.
--
Peter Jeremy
Please excuse any delays as the result of my ISP's inability to implement
an MTA that is either RFC2821-compliant or matches their claimed behaviour.
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