I have a Riverbed SteelApp (StingRay) load balancer managing one of our clients web traffic, the client now wants an additional internet feed to create a new service.
How is it possible to add another outside internet feed into the SteelApp load balancer for this new service, I assume it's all down to linux iptables and routing but wanted to confirm before I started to create interfaces on the load balancer.
SteelApp has no conditions that limit the number of internet links that the customer can have since it's not terminating any of them
You are correct in that all you need to do is add the additional interface and begin advertising/creating services. The SteelApp is not acting as a router or (redirecting layer 3 services for that matter) from the SteelApp Applications' perspective. So the work of route table separation/partitioning would be a function of iptables if you are running on a Software Linux variant.
You may want to consider Web Application Firewall services for your customer to protect these service advertisements at the Application Layer!