Debuntu

Let’s continue the network monitoring serie with yet another use case…. the “What program is using my bandwidth?” problem while not imposible to solve, still remains a pain. What if there were some kind of top for network?

NetHogs is a nifty tool that will do that for you and will help you finding what is hogging your connection.

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There is many tools out there that help in monitoring network usage, collect statistics and generate graphs so we can view what happened at a given date/time. Anyhow, finding the bandwidth usage over an hour/day/week/month can be really tricky.

vnstat is a suite of daemon and client programs that monitor network bandwidth usage.

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OpenVPN is a SSL based VPN software that runs on most OS. It is simple to install and run.

In this tutorial, I will go over the steps needed to configure OpenVPN on Debian Squeeze to provide a full VPN tunnel, this is particularly useful when you want to access internet from non-trusted networks such as free hotspots…

There are many ways of setting up OpenVPN, a common one is to use a unique certificate for each users. Another one is to have each user authenticate with a username/password.

In this article, we will be setting OpenVPN to authenticate users using PAM.

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Using freeradius for authentication

Here I am going to consider that the freeradius server is set up correctly, meaning that you can already authenticate your users with freeradius using radtest utility.

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XL2TP

Now, let’s get on the next phase: XL2TP.

Packages Requirements

You can install xl2tp with the following command:

# apt-get install xl2tp

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Even though I pretty like OpenVPN, there is still some devices that might not support the TUN/TAP driver needed by OpenVPN.

Take IPhones, Android phones for instance, you need to root them in order to get that feature, assuming somebody has already cooked a ROM for your device.

L2TP is quite and old standard that allow setting up VPNs.

On the other end, it does not provide any kind of encryption mechanism, and as such, it is pretty common to get L2TP running over an IPSec link.

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I was trying network-manager-openvpn plugin today on Lucid, I could import my configuration, DNS was set up correctly upon connection/disconnection, route imported correctly (almost ).

One issue though is that it was also changing the default route to the VPN tunnel while this should not happen.

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Lately, I have been experiencing a funny network issue when using VMware Workstation VMs with NAT interface. Roughly, the IP network was working fine, but DNS resolution was not anymore. It happened intermittently, but I could see that this mainly happened when I was suspending my laptop, going to another location and resuming.

Forcing the VM to use a public DNS would solve the issue.

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5. Configuring Dovecot

Dovecot has its SQL configuration gathered in a separated file: /etc/dovecot/dovecot-sql.conf, so let’s edit edit with our settings:

# vi /etc/dovecot/dovecot-sql.conf

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4. Configuring Postfix

4.1. main.cf and master.cf

Your postfix main.cf file should look like:

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