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Re: CARP and VRRP incompatible on the same network segment?

On Oct 19, 2005, at 6:21 PM, Zack Lawson wrote:

Hey everyone,

I am having an issue where CARP interfaces on the same network segment
as VRRP interfaces (on our ISP's routers) are causing the CARP
interfaces to malfunction.

I also get the following errors in /var/log/messages:

/bsd: carp: received len 8 < 36 on carp2
last message repeated 3005 times

When nating through this carp interface, I get packet loss up to 45%.
When using the same IP, but through a non-carp interface, I no problems

Anyone have any ideas? Should CARP and VRRP be able to function on the
same network segment?

I wouldn't be surprised if they're incompatible on the same segment. They use the same protocol number, and I'm willing to be you have identical VRID/VHID's in there. Even if the ID's are not the same, the OS is trying to make sense of what it believes to be a CARP packet, but really isn't. The CARP packet format is described in src/ sys/netinet/ip_carp.h. The VRRP packet format is in the RFC (http:// www.faqs.org/rfcs/rfc2338.html).

Jason Dixon
DixonGroup Consulting