# CARP across two jails on one host



## amweeden06 (Jul 22, 2010)

My box is running FreeBSD version 8.1-PRERELEASE.  I've created two jails and want them to be able to share an IP address via CARP.

As I understand it, each host must use the same VHID and IP address on its carp interface in order to work as a failover for the other hosts.

I'm also under the impression that jails cannot create interfaces, as my attempt to run [cmd=]ifconfig carp0 create[/cmd] within a jail returned the error 
	
	



```
ifconfig: SIOCIFCREATE2: Operation not permitted
```

I'm wondering, then, if it's possible to use CARP across two jails on a single host, since attempting to create two carp interfaces with the same vhid on the parent produces the error 
	
	



```
ifconfig: SIOCSVH: File exists
```

Does anyone here have experience running CARP in jails?


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## vivek (Jul 23, 2010)

You can't do that inside jail  crap works directly at host level and it needs to send health check continuously. carp is more suitable for firewall failover or reverse proxy load balancer such as nginx.


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