Switching Networks & IP Ranges Out (2 NICS, 2 SUBNETS)

I need to migrate servers to new IP addresses. My server has 2 NICS and I just connected the eth1 today nothing yet configured for eth1.

eth0 is active, (default settings)
eth1 is inactive

vmbr0 is active with eth0 under the ports/slaves with ip 38.81.xxx.2 and gateway of 38.81.xxx.1

I want to make eth1 active and add a vmbr1 but proxmox says there is already a default gateway and gives an error.

What do I do so I can start assigning my NEW IP Addresses to this second eth1 port?

Thanks
Marc P.