How IP-Aliases does work on Google Cloud Computing Instance?

Question

When setup a IP-Alias via gloud command or the interface, it works out of the box. But in the machine itself, i do not see any configuration, ip addr-entries, no firewall rules, no routes that would allow to be the machine pingable - but it's pingable (local and remote)! (for example 10.31.150.70, when you setup a 10.31.150.64/26-subnet, and you primary IP is 10.31.150.1) On the other hand, the primary IP of the machine is a /32-Netmask. For example: 10.31.150.1/32, Gateway: 10.31.0.1/16. So, how can the machine reach the gateway, 10.31.0.1, when the gateway is out of the range? When removing the Main-IP via ip addr del, the aliases aren't pingable anymore. JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

Google runs a networking daemon on your instance. It runs as the google-network-daemon service. This code is open source and viewable at this repo. This repo has a Python module called google_compute_engine which manages IP aliasing among other things. You can browse their code to understand how Google implements this (they use either ip route or ifconfig depending on the platform) To see the alias route added by Google on a Debian box (where they use ip route underneath for aliasing) run the following command. ip route ls table local type local dev eth0 scope host proto 66 If you know your Linux commands, you can remove appropriate routes after stopping the daemon, and then assign the alias IP address to your primary interface as the second IP address to see the ifconfig approach in action as well.