check ip rotation

Hi all,
I configured ip rotation on exim mail server by modifying the /etc/exim.conf file. I want to check whether the ip address rotating or not. Can any body show me how can i find out is it rotating or not.

Thanks,

Hi,
I done the ip rotation of my exim mail server. By using following modification in /etc/exim.conf file

begin transports

route_smtp:
driver = smtp
interface = 72.9.108.234${eval:${substr{-2}{1}{$tod_zulu}}%5+4}

But How can i find out whether is it working or not. Please tell me if anybody knows about this.

Thanks,