carpX: incorrect hash with IP aliases

[Max Laier]

On Tuesday 03 March 2009 15:57:50 Eirik Øverby wrote:
> Hi,
>
> whenever I configure an extra IP on one of my CARP interfaces, traffic
> on that particular subnet slows to a crawl (the primary IP of the
> interface is the gateway IP), and I get lots of
>   carp4: incorrect hash
> in dmesg.
>
> I see this issue referenced also in
>    http://lists.freebsd.org/pipermail/freebsd-net/2008-March/017160.html
> and there are suggestions this is a known issue - however I still see
> it in FreeBSD 7.1 (pfSense 1.2.3-prerelease). I cannot find a PR on
> this, but my searching skills may be inadequate..

You might be referring to http://www.freebsd.org/cgi/query-pr.cgi?pr=121574 
which should have been fixed with rev 1.54 (MFC'ed in 1.52.2.1 to RELENG_7) of 
ip_carp.c

> Am I doing something wrong? I tried assigning the alias with both /32
> and /24 netmasks.

Make sure that you are configuring the same aliases with the same netmasks on 
all members of the carp group - preferably before bringing the interface up 
for the first time (though it should properly recalculate the hashes as you 
add aliases).  As you seem to be using pfsense you might want to check with 
them to make sure they have the fix in their build - though I recall it was a 
joined effort back then.

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