CARP question (interpretation clarification)
awebster at connectalk.com
Wed Feb 15 19:19:42 PST 2006
On FreeBSD 5.4-p8, the man page for CARP(4), has a paragraph about
net.inet.carp.preempt which reads :
net.inet.carp.preempt Allow virtual hosts to preempt each
is also used to failover carp interfaces
group. When the option is enabled and
the carp enabled physical interfaces goes
advskew is changed to 240 on all carp
faces. See also the first example.
If I understand this correctly, a system having multiple carp interfaces
would either see all carp interfaces as all MASTER or all BACKUP, but
not a combination of both?
On my system, I've got preempt turned on, but as shown below on my
"backup" machine, two carp interfaces are in BACKUP config, and one is
On the "master" machine of this pair, I have the reverse, two MASTER,
and one BACKUP corresponding to the appropriate subnets.
Am I misinterpreting the documentation, or does the preempt function not
work the way I expected it to?
r2# sysctl -a | grep preempt
r2# ifconfig -a
carp0: flags=41<UP,RUNNING> mtu 1500
inet 172.16.0.230 netmask 0xfffffc00
carp: BACKUP vhid 1 advbase 1 advskew 100
carp1: flags=41<UP,RUNNING> mtu 1500
inet 172.16.20.230 netmask 0xfffffc00
carp: BACKUP vhid 20 advbase 1 advskew 100
carp2: flags=41<UP,RUNNING> mtu 1500
inet 10.10.88.1 netmask 0xffffffe0
carp: MASTER vhid 88 advbase 1 advskew 100
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