Asymmetric Routing on AWS EC2. Attaching two or more network interfaces (ENIs) from the same subnet to a non-Amazon Linux EC2 instance (for example, CentOS or RedHat Linux) might encounter traffic flow issues caused by asymmetric routing and Linux settings. The solution is to utilize iproute2 package two-phase routing infrastructure. First, we need to create two routing rules that select the routing table that sends the server's response traffic out the same interface on which the request arrived. Second, we create two routing tables; each table routes out through a different interface. The source address of the outgoing packets can be used for the route rules as the selector.
Linux connection limit. Many users would like to know what's the TCP connection limits on Linux instance and how to increase the number of connections. This article explains the configurations needed to check and modify on Linux to increase the maximum TCP connection in terms of server side and client side. Also, some tests were done to see the result with different configurations on Amazon Linux.