load balancing with pen

I am trying to load balance a couple of servers using "pen." Anybody
have any luck?
I have a customer facing IP that comes into a netgear router which has
two servers on the inside network.

One server is a Solaris box with two IP addresses. One server has
192.168.1.10, the other IP on the solaris box is in a solaris zone.
The zone IP is 192.168.1.110. Both IPs have apache2 running on their
respective port 80. The other server is running fedora8 and running
apache2. It's IP is 192.168.1.20.

Each website is accessible on the inside network.

I have tried starting pen with the following command:

pen -f 192.168.1.10:80 192.168.1.10:80 192.168.1.110:80
192.168.1.20:80

I have the netgear router forward port 80 to 192.168.1.10:80. It
gives me the .10 address at first (sometimes, not always), then
forwards me to .110 and doesn't change. If I take apache offline on .
110, I get a timeout/server unavailable.

Can anyone help, or point me in the right direction.

thanks

Mike