Release It!, 2nd Edition

Network Routing

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.

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 ...