Masquerade more then one IP address on WAN interface

We have a wireless Guest network that uses the UTM9 (SG650) to masquerade the internal IP addresses to the public IP on eth7. (many-to-one NAT)

The bandwidth of this Internet circuit is 1GB. At peak usage times, users sometimes cannot access the Internet. (page can’t be displayed). As the circuit peaks at about 100Mb, we believe the problem is the public IP address on eth7 is overwhelmed with users, exhausting all tcp ports available.

This can be avoided by adding an additional IP address to the pool that masquerades. I tried adding an alias to eth7, but I can’t tell if it’s working. Or, if this configuration is even possible.

Other network elements have this configuration option.

Thanks,

Jerry