Networking

If you’re keeping in touch with new services provided by AWS, you probably heard about new security monitoring tool: GuardDuty. You probably also noticed a whole new family of Elastic Load Balancers (v2), which includes Network Load Balancers (NLB). Deploying those two new services may generate some unexpected results - and here’s why.

When using AWS Elastic Load Balancer with TCP listeners (not HTTP or HTTPS), the biggest problem faced by many people is the lack of client’s IP address. Since it’s TCP which works on a lower layer, the ELB does not add the X-Forwaded-For header (like it does for HTTP and HTTPS). For some time, this meant that if you used those listeners, you had no way of getting the original client’s IP address.