How to Install and Configure MRTG on Ubuntu Server 12.04

This post will describe how to install and configure Tobi Oetiker’s MRTG (Multi Router Traffic Grapher) on your Ubuntu home server. Once configured, you’ll be able to use it to monitor the traffic in and out of your home network using the SNMP capability in your network’s gateway\router. MRTG generates static HTML pages containing PNG images which provide a visual representation of this traffic. MRTG typically produces daily, weekly, monthly, and yearly graphs. MRTG is written in perl and works on Unix/Linux as well as Windows. MRTG is free software licensed under the GNU GPL.

Software versions used in this post were as follows:

Ubuntu Server v12.04 x64 LTS)

mrtg_2.17.3-2ubuntu1_amd64.deb

Download and Install

First, download and install MRTG:

sudo apt-get install mrtg

If this is the first time installing MRTG on your server you’ll likely be presented with the following message. Answering “Yes” means that the default configuration file will be installed with permissions set at 640. Answering “No” means that the permissions are set at 644. In this example we’re going to accept the default Yes. No worries though, if you select No the steps in this tutorial will still work.

Passive-interface command behavior in RIP, EIGRP & OSPF

Passive-interface command is used in all routing protocols to disable sending updates out from a specific interface. However the command behavior varies from o­ne protocol to another.

In RIP this command will disable sending multicast updates via a specific interface but will allow listening to incoming updates from other RIP speaking neighbors.

This simply means that the router will still be able to receive updates o­n that passive interface and use them in the routing table.

In EIGRP the passive-interface command stops sending outgoing hello packets, hence the router can not form any neighbor relationship via the passive interface. This behavior stops both outgoing and incoming routing updates.

In OSPF the passive-interface has a similar behavior to EIGRP. The command suppresses hello packets and hence neighbor relationships.

Configuring the Cisco IDS Router / Switch Modules for Cisco 6500 Switch / 7200 Router

IDSM-2

The IDSM-2 Module is a Cisco IDS blade for the Cisco 6500 switch.
Once you install the module into the switch the module uses following logical ports :

Port 1	Used for TCP Resets (In Promiscuous Mode)
Port 2	Command and Control
Port 7	Sensing Port
Port 8	Sensing Port

Below details the steps required for configuring your switch / module for an inline setup. This includes obtaining the module number for the cisco ids running the setup wizard and then assigning the required ports for on the switch for ids sensing within an inline configuration. The clear trunk commands are required as by default the switch assigns the ports as trunk ports to every vlan.

How to configure a Cisco Layer 3 switch-InterVLAN Routing

Cisco Catalysts switches equipped with the Enhanced Multilayer Image (EMI) can work as Layer 3 devices with full routing capabilities. Example switch models that support layer 3 routing are the 3550, 3750, 3560 etc.

On a Layer3-capable switch, the port interfaces work as Layer 2 access ports by default, but you can also configure them as “Routed Ports” which act as normal router interfaces. That is, you can assign an IP address directly on the routed port. Moreover, you can configure also a Switch Vlan Interface (SVI) with the “interface vlan” command which acts as a virtual layer 3 interface on the Layer3 switch.

On this post I will describe a scenario with a Layer3 switch acting as “Inter Vlan Routing” device together with two Layer2 switches acting as closet access switches.