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
- and/or setup high availability using a third party load balancer before both Gateways (we recommend using DNS Round Robin)