CARP master election changed in 11.0 ?

[Robert Blayzor]

Disregard, this problem has been semi-solved. For reasons unknown now it was due to carp send error penalties being applied to one of the servers, which are added to the advskew.

Since a lagg interface is involved:

carp: demoted by 10 to 10 (send error 50 on lagg0)
carp: demoted by 10 to 20 (send error 50 on lagg0)


But what is strange is that the two servers in the VHID have the same exact hardware. Experiencing this send error on one but not the other…

Ultimately the work around was adjusting
net.inet.carp.senderr_demotion_factor -> 10

From it’s default of 240.


Since these errors appear only at startup and not incrementing, it doesn’t really look like a problem.


net.inet.carp.ifdown_demotion_factor: 240
net.inet.carp.senderr_demotion_factor: 10
net.inet.carp.demotion: 20


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> On Dec 1, 2016, at 3:10 PM, Robert Blayzor <rblayzor.bulk at inoc.net> wrote:
> 
> Did something change between 10.x and 11.0 with carp MASTER election and advskew? 
> 
> I have several 10.3 servers where the master is elected based on the member with the LOWEST advskew.
> 
> From a pair of 10.3 servers:
> 
> 	vlan: 100 parent interface: lagg0
> 	carp: MASTER vhid 10 advbase 1 advskew 100
> 
> 	vlan: 100 parent interface: lagg0
> 	carp: BACKUP vhid 10 advbase 1 advskew 110
> 
> 
> Deploying a new pair of 11.0-RELEASE servers, I see the opposite; seems like the member with the HIGHEST advskew wins now:
> 
> 
>        carp: BACKUP vhid 20 advbase 1 advskew 0
> 	groups: lagg
> 
> 	carp: MASTER vhid 20 advbase 1 advskew 100
> 	groups: lagg
> 
> 
> 
> Preemption doesn’t seem to matter, even with preemption enabled. (which it is).
> 
> From OpenBSD, man reads:
> 
> advskew
> This optional parameter specifies how much to skew the advbase when sending CARP advertisements. By manipulating advskew, the master CARP host can be chosen. The higher the number, the less preferred the host will be when choosing a master. The default is 0. Acceptable values are from 0 to 254.
> 
> 
> And this seems true in 10.3 but reversed in 11.0 ?
> 
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> 
> 
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