PF - Carp and vhid limitations

Michael K. Smith - Adhost mksmith at
Wed Dec 5 12:05:39 PST 2007

Hello All:

I'm interested in using PF to front a web farm where there will be lots of static IP addresses for SSL affinity.  As such, I expect to have many more than 255 CARP interfaces.  But, as I understand it, I'm limited to 255 vhid's and I have to have a discreet vhid per CARP interface.

Is there a way to configure my CARP interfaces such that I can get around this limitation?  Right now, I configure everything as:

ifconfig_carp5="inet netmask vhid 5 advskew 0 pass mypass"
ifconfig_carp6="inet netmask vhid 6 advskew 0 pass mypass"

and so on.

I'm wondering if there is a way to alias IP addresses in the same subnet "ifconfig_carp5_alias" or something similar.  It seems like there is a reuse mechanism in OpenBSD because you can associate a carpdev to the entry, but I don't see that in FreeBSD.


Michael K. Smith, GISP
mksmith at
w: +1 (206) 404-9500 f: +1 (206) 404-9050
PGP: B49A DDF5 8611 27F3  08B9 84BB E61E 38C0 (Key ID: 0x9A96777D)

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