Network Routing
Learn about backend and front end network interfaces, the subnets, routing issues, static route definition, and software defined networking.
Network interfaces
Because machines in a data center usually have multiple network interfaces, questions will sometimes arise about which interfaces particular kinds of traffic should traverse. For example, it’s relatively common to see a machine with a front-end network interface connected to one VLAN for communication to the web servers and a back-end network interface connected to a different VLAN for communication to the database servers. In this case, the server must be told which interface to use in order to reach a particular destination IP address.
The different subnets
In the case of nearby servers, the routes are probably easy. They’ll just be based on the subnet addresses. In the example of the application server, the back-end interface probably shares a subnet with the database server, while the front-end interface probably shares a subnet with the web servers. Routing gets a bit more complicated with distant services because they may involve third-party services.
Packets reaching their destination
Modern operating systems strive to make routing automatic and invisible. When a machine brings up its primary NIC (whichever one it identifies as primary, anyway), it uses the main IP address for that ...