carp/vrrp/ucarp advice
- From: "Ross Draper" <ross@xxxxxxxxxxxxxxx>
- Date: Mon, 26 Mar 2007 08:31:21 +0100 (BST)
Hi guys
I was wondering if I could get some advice from those of you who have
successfully implemented ip address failover systems such as carp and
freevrrpd.
I am trying to set up a high availability web loadbalancer using a pair of
freebsd 6.2 boxes. I have tried a number of ways to perform failover but
always seem to be hitting a problem.
UCARP
Pro's:This would be my ideal solution as the startup/shutdown scripts
enable me to stop and start my applications and add aliases to adaptors
easily.
Cons: When the backup box is rebooted it always seems to come up
advertising itself as the master, then after a few seconds reverts to
backup, although I was under the impression it was supposed to wait and
listen for advertisements(it doesnt seem to)to see if a master exists. Its
initial gratuitous arp as a master is sufficient to poison any traffic
from the local router to the shared ip address. Only solution was to use
arp-sk to send gratuitous arps every few secs, however, arp-sk was a bit
flakey and it was a bodge.
CARP
Pro's: stable and built into the kernel. Could enable acive/active arp
load sharing at a later point.
Cons: There is a Freebsd bug (I've seen it discussed on the lists) where
the creation and destroyal of a carp interface causes a kernel panic.
Also, there is no support for start/stop scripts.
Freevrrpd
Pros: Mac address changing removes some of the arp timeout
issues/gratuitus arp problems and it supports start/stop scripts
Cons: I'm finding that upon rebooting the backup unit it correctly starts
as a backup, then three seconds later syslogs that it is the master and
changes its mac address accordingly. although a sniff of the network
traffic indicates it is sending the right advertisements, it never goes
into backup mode again and keeps the virtual mac address.
So, what am I doing wrong? are there more suitable options? the
loadbalancers are all single homed and I have tried a mixture of xl, bge
and fxp cards.
Also, any links to a perl based gratuitous arp utils would be great
Any help/suggestions much appreciated.
Ross
PS - I mailed this to freebsd-cluster earlier but it didnt seem to make it
onto the list - apologies if this ends up as a cross post.
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