Optimizing performance using 'ping'

In this recipe, we will use the low-level ping command to determine the optimal Maximum Transfer Unit (MTU) size for our OpenVPN setup. Finding the right MTU size can have a tremendous impact on performance, especially, when using satellite links, or even some cable/ADSL providers. Especially, broadband connections using the PPPoE (PPP over Ethernet) protocol often have a non-standard MTU size. In a regular LAN setup, it is hardly ever required to optimize the MTU size, as OpenVPN's default settings are close to optimal.

Getting ready

Make sure the client and the server computers are connected over a network. For this recipe, the server computer was running CentOS 5 Linux. The client was running Fedora 13 Linux, but instructions for a Windows client are given as well.

How to do it...

1. We first verify that we can reach the server from the client:

   [client]$ ping –c 2 <openvpn-server-ip>
   

   This will send two ICMP ping packets to the server and two replies...