Using CARP with multiple IP aliases (FBSD 10.0)

[Peter Wemm]

On Thursday, September 11, 2014 05:34:57 PM Steven Hartland wrote:
> ----- Original Message -----
> From: "Freddie Cash" <fjwcash at gmail.com>
> To: "Steven Hartland" <killing at multiplay.co.uk>
> Cc: "FreeBSD Stable" <freebsd-stable at freebsd.org>
> Sent: Thursday, September 11, 2014 5:24 PM
> Subject: Re: Using CARP with multiple IP aliases (FBSD 10.0)
> 
> > On Thu, Sep 11, 2014 at 8:54 AM, Steven Hartland <killing at multiplay.co.uk>
> > 
> > wrote:
> >> I believe you need a seperate vhid per IP assuming you want each to fail
> >> over
> >> to another machine when it goes down e.g.
> >> ifconfig igb0 inet 1.2.3.4/24 vhid 30 pass mypass
> >> ifconfig igb0 inet 1.2.3.5/32 vhid 31 pass mypass alias
> >> ifconfig igb0 inet 1.2.3.6/32 vhid 32 pass mypass alias
> >> ifconfig igb0 inet 1.2.3.7/32 vhid 33 pass mypass alias
> > 
> > ifconfig igb0 inet 1.2.3.8/32 vhid 34 pass mypass alias
> > 
> > 
> > ​That's what I'm trying to avoid.  :)  And everything appears to get added
> > to the interf>
> 
> > ace correctly:
> I can't say I've used it in that way and I'm not sure how carp decides how
> to fail over when it has multiple IP's available.
> 
> I can confirm you don't need all the params when adding an IP to vhid.
> so you can for example configure the vhid and then add the IP's or do
> as you have done and configure it on the first IP.


This is the method we use extensively in the freebsd.org cluster.  eg: the 
routers have public IP addresses, private RFC1918, IPv6 etc addresses, all on 
the same vhid for each interface.

* One vhid presence, with multiple aliases on the same vhid.
* Configure vhid params once, aliases attached without params.

carp state checking uses link local addresses to communicate.

Having multiple IP's per vhid means they change master->backup state as a 
group, not individually and that's what we wanted for things like router 
default gateways.

-- 
Peter Wemm - peter at wemm.org; peter at FreeBSD.org; peter at yahoo-inc.com; KI6FJV
UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246
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