Vrrp/CARP/ucarp Problems

[Ross Draper]

Hi All
 
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 comes 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). The backup boxes 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/gratuitous 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(lower
priority), it never goes into backup mode again.
 
So, what am I doing wrong? Are these common problems, or something that
appears specific to my hosts/switches? are there more suitable options?
The loadbalancers are all single homed and I have tried a mixture of xl,
bge and fxp cards.  
 
Any help/suggestions much appreciated, also, any links to a perl based
gratuitous arp util would be great!
 
Many thanks

Ross 

PS - Apologies if you see multiple copies of this message, I seem to be
having trouble getting mails onto the list.



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