Does anyone know how AWS ELB with SSL work behind the scenes? Running an nslookup on my ELB’s domain name I get 4 unique IP addresses. If my ELB is SSL enabled, is it possible for AWS to share these same IPs with other SSL enabled ELBs (not necessarily owned by me)?
As I understand it the hostname in a web request is inside of the encrypted web request for a https request. If this is the case, does AWS have to give each SSL-enabled ELB unique IP addresses that are never shared with anyone else’s SSL ELB instance? Put another way — does AWS give 4 unique IP addresses for every SSL ELB you’ve requested?
Elastic Load Balancing (ELB) employs a scalable architecture in itself, meaning the number of unique IP addresses assigned to your ELB does in fact vary depending on the capacity needs and respective scaling activities of your ELB, see section Scaling Elastic Load Balancers within Best Practices in Evaluating Elastic Load Balancing (which provides a pretty detailed explanation of the Architecture of the Elastic Load Balancing Service and How It Works):
This is further detailed in section DNS Resolution, including an important tip for load testing an ELB setup:
The entire topic is explored in much more detail within Shlomo Swidler’s excellent analysis The “Elastic” in “Elastic Load Balancing”: ELB Elasticity and How to Test it, which meanwhile refers to the aforementioned Best Practices in Evaluating Elastic Load Balancing by AWS as well, basically confirming his analysis but lacking the illustrative step by step samples Shlomo provides.