Assistance with setting up an LTSP (Edubunt) server in KVM

Hello,

We use Proxmox 2.1. I have two network cards on my Host server, eth0 and eth1.

In networking on the Proxmox Gui I have assigned vmbr0 to eth0 setup with IP 192.168.4.5. My Gateway is 192.168.4.1
I can ping 192.168.4.5 and my Virtual guests can access the internet and other computers on my network.

Also in networking on the Proxmox Gui I have assigned vmbr1 to eth1 setup with IP 192.168.5.5. I have not assigned a gateway for this (If I try I get an error that vmbr0 already has a gateway).
I cannot ping 192.168.5.5.

What I want to have for my setup is to use vmbr0 (eth0) connected to my local network and vmbr1 (eth1) connected to a switch. This switch is used to connect my Thin Clients to the LTSP Server. My plan is to use clients connected to LTSP server to be able to rdesktop to computers in my network.

What have I done incorrectly to get the vmbr1 (eth1) setup for the way I need to use it.

Thank you.