TMG not using assign ip address

Hi,

I just install TMG with this IP address 192.168.5.40

I also have addtional Ip address 192.168.5.45, 48, 19

After adding 192.168.5.19

I can't use RSA on the serevr.

I have done some research to found out why this is happening. lot of the forum talking about tmg use the lower ip address which is 192.168.5.19 to make it use specif ip address i need to use enat.

I went into tmg -> Networking -> Network Rule

Name: Internet Access

Relation: NAT

Destination Network: External

When I try to set the default IP address in this section i dont see anything under

properties -> NAT Address Selection -> Use the specified IP address

How to I see these ip address and select one of them as default which will be used all of the time.