CARP on VMware ESX

Christian Ullrich chris at
Fri Dec 5 00:25:07 PST 2008

Hello all,

I'm having trouble getting a CARP setup to work on VMware ESX. The 
problem: As soon as I configure the CARP interface, it first goes to 
MASTER state, then immediately drops to BACKUP, and stays there.

Right now I have only one VM set up, so the reason is not that there's 
an active master in the group.

In the log I get the message

	arp_rtrequest: bad gateway (!AF_LINK)

about once every three or four seconds. Just as often, I see ARP 
requests from the above IP, querying for the same address.

I know about VMware and allowing promiscuous mode on the "physical" 
interface. But this is where it gets confusing: If I create the CARP 
interface while promiscuous mode is _not_ allowed on the interface, it 
starts up fine, becomes master, the route entry appears, and everything 
looks fine. Once I then allow the interface into promiscuous mode, I can 
use it fine.

If promiscuous mode is already permitted on the interface when I start 
CARP, I get what I described above: The interface is in BACKUP state, 
the route to the CARP interface doesn't show up, and I get both the ARP 
requests and the error message continuously.

I appreciate any hints.

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