Monitoring Netflow Using nfdump/nfsen

$ sudo apt-get update $ sudo apt-get install build-essential autoconf $ sudo apt-get install rrdtool mrtg librrds-perl librrdp-perl librrd-dev \

libmailtools-perl php5 bison flex

Now proceed to download and build. Note that only the last step (make install) has to be done as root.

$ cd $ wget ​http://www.ws.nsrc.org/downloads/nfdump-1.6.13.tar.gz $ tar xvzf nfdump-1.6.13.tar.gz $ cd nfdump-1.6.13 $ ./configure --help # optional, shows the build settings available $ ./configure --enable-nfprofile --enable-nftrack $ make $ sudo make install

Testing nfcapd and nfdump

$ mkdir /tmp/nfcap-test $ nfcapd -E -p 9001 -l /tmp/nfcap-test

... after a while, a series of flows should be dumped on your screen.

Stop the tool with CTRL+C, then look at the contents of /tmp/nfcap-test

$ ls -l /tmp/nfcap-test

You should see one or more files called nfcapd.<YEAR><MON><DAY><HR><MIN>

Process the file(s) with nfdump:

nfdump -r /tmp/nfcap-test/nfcapd.201Ywwxxyyzz | less nfdump -r /tmp/nfcap-test/nfcapd.201Ywwxxyyzz -s srcip/bytes

You should get some useful information :) Installing and setting up NfSen

Download and compile. The patch is to fix a problem reported at ​http://sourceforge.net/p/nfsen/bugs/31/

$ cd $ wget ​http://www.ws.nsrc.org/downloads/nfsen-1.3.6p1.tar.gz $ tar xvzf nfsen-1.3.6p1.tar.gz $ cd nfsen-1.3.6p1 $ wget ​http://www.ws.nsrc.org/downloads/nfsen-socket6.patch $ patch -p0 < nfsen-socket6.patch $ cd etc $ cp nfsen-dist.conf nfsen.conf $ editor nfsen.conf

Set the $BASEDIR variable

$BASEDIR = "/var/nfsen";

Set the users appropriately so that Apache can access files:

$WWWUSER = 'www-data'; $WWWGROUP = 'www-data';

Set the buffer size to something small, so that we see data quickly. You would not do this on a production system.

# Receive buffer size for nfcapd - see man page nfcapd(1) $BUFFLEN = 2000;

Find the %sources definition, and change it to:

%sources=( 'rtrX' => {'port'=>'9001','col'=>'#0000ff','type'=>'netflow'},

);

(substitute your group's router for rtrX, and either remove or comment out the existing sample sources).

Change the HTMLDIR from /var/www/nfsen/ to /var/www/html/nfsen/

$HTMLDIR = "/var/www/html/nfsen/";

Now save and exit from the file. Create the netflow user on the system

$ sudo useradd -d /var/nfsen -G www-data -m -s /bin/false netflow

Install NfSen and start it

Change directory back to just inside the source directory:

$ cd $ cd nfsen-1.3.6p1

Now, finally, we install:

$ sudo perl install.pl etc/nfsen.conf

Press ENTER when prompted for the path to Perl. Install init script

In order to have nfsen start and stop automatically when the system starts, add a link to the init.d diretory pointing to the nfsen startup script:

$ sudo ln -s /var/nfsen/bin/nfsen /etc/init.d/nfsen $ sudo update-rc.d nfsen defaults 20

Start NfSen

$ sudo service nfsen start

Check that nfcapd processes have been started:

$ ps auxwww | grep nfcapd

View flows via the web:

You can find the nfsen page here:

​http://pcX.ws.nsrc.org/nfsen/nfsen.php

If you are working in pairs, then both of you should point your web browser to the PC which is receiving flows.

You may see a message such as:

Frontend - Backend version mismatch!

This will go away if you reload the page, it's not a problem.

Done! Move on to the third lab, exercise3-nfsen-top-talkers NOTES Adding sources

If you had multiple routers in your network all sending flows to the same collector, you can either configure them to send to different ports on the collector, or you can tell nfsen the source IP address of each router. This allows nfsen to show distinct data from each source.

DON'T DO THIS NOW as you only have a single router, but if you needed to, you would do it as follows:

edit /var/nfsen/etc/nfsen.conf, and add the source(s), for example:

%sources = (

'rtrX' => { 'port' => '9001', 'col' => '#0000ff', 'type' => 'netflow' }, 'rtrY' => { 'port' => '9002', 'col' => '#00ff00', 'type' => 'netflow' }, 'gw' => { 'port' => '9996', 'col' => '#ff0000', 'type' => 'netflow' },

);

Reconfigure NfSen.

You will need to run this every time you modify /var/nfsen/etc/nfsen.conf:

$ sudo /etc/init.d/nfsen reconfig

You should see:

New sources to configure : gw rtrY Continue? [y/n] y

Add source 'gw' Add source 'rtrY'

Start/restart collector on port '9002' for (rtr2)[pid] Start/restart collector on port '9996' for (gw)[pid]

Restart nfsend:[pid]

perl -MCPAN -e 'install Socket6' vi libexec/NfSenRRD.pm 1.5 to 1.6