If you want to avoid having a single gateway server - thus risking a single point of failure -, 

you can activate the gateway portal and load balancing on a second server of your load balanced farm - to provide a failover to your farm -.

Activating a second gateway portal web feature :

Enabling load balancing on your second gateway portal server :

All you have to do is replicate your load balancing configuration on your second server.


Once it's done, you may either provide: 

- the alternate URL to your users,

- and/or generate a new connection client that points to the new gateway.