Linux Mrtg Configuration How

Linux MRTG Configuration HOW-TO Introduction MRTG is wonderful tool. You can use it to monitor traffic on your router or leased server located at remote IDC. Since it is written in Perl and some code in C language, it is portable and high performance tool.

What is MRTG? As explained in official mrtg(1) man page "The Multi Router Traffic Grapher (MRTG) is a tool to monitor the traffic load on network-links. MRTG generates HTML pages containing GIF images which provide a LIVE visual representation of this traffic." Here is public view of my own site. Please note following discussion based upon Red Hat Linux Enterprise version 3 update 2 and RHEL v4.0.

What is SNMP and why should I care? SNMP is Simple Network Management Protocol. It is use to manage IP network devices such as servers, routers, switches etc. Administrator can find or manage network performance, solve problem or even optimize it further. For more information on official UNIX/Linux SNMP please see UCDSNMP/NET-SNMP Tutorials and an excellent resource at Snmplink.org

Assumptions These installation instructions assume you have: • •

•

•

Linux distribution You would like to perform MRTG and snmp binary installation using rpm. If you are looking for source installation then visit author's web site here. This page has an excellent information (systematically) to install it from source. Required RPMs o mrtg o snmp o snmp-utils Installations were tested on Red Hat Enterprise Linux version 3 update 2.

Configuration Make sure snmp server is working. Without proper working snmp server, mrtg will not work. Therefore, first step is make sure snmp up and running. Following steps will take you gradually to configure it. • • • • • • •

Step # 1: Make sure snmp server installed Step # 2: Determine if snmp server is running or not Step # 3 Make sure snmp server configured properly Step # 4 Install mrtg if not installed Step # 5 Configure mrtg Step # 6 First test run of mrtg Step # 7: Create crontab entry so that mrtg graph / images get generated every 5 minutes

• •

Step # 8: Block ports 161, 162 udp at firewall. Step # 9: Optional protect your MRTG graphs/html pages with password protected directory

Step # 1 : Make sure snmp server installed Please note that snmpd configuration does not require using mrtg with remote network devices such as Routers and switches. If you just want mrtg graphs for router or switch then please refer to step # 4 (as all these devices comes preconfigured with snmpd software). Run rpm commands query option to find out snmp server installed or not: # rpm -qa | grep snmp

If snmp installed then please refer step # 2; otherwise snmp server and utils were not present and your need to install them using following steps (login as a root user): (a) Visit rpmfind.net to get snmp server and utilities rpms. If you are fedora user then use yum command as follows to install it: # yum install net-snmp-utils net-snmp

(b) If you are RHEL subscriber then use up2date command as follows to install: #up2date -v -i net-snmp-utils net-snmp

Step # 2 : Determine if snmp server is running or not Run 'ps' command to see if snmp server is running or not: # ps -aux | grep snmp

Output: root

5512

0.0

2.3

5872 3012 pts/0

S

22:04

0:00 /usr/sbin/snmpd

Alternatively, you can try any of the following two commands as well: # lsof -i :199

Output: COMMAND PID USER snmpd 5512 root

FD 4u

TYPE DEVICE SIZE NODE NAME IPv4 34432 TCP *:smux (LISTEN)

OR try out netstat command: # netstat -natv | grep ':199'

Output: tcp

0

0 0.0.0.0:199

0.0.0.0:*

LISTEN

If you found service is running or listing on port 199 then please see step #3; otherwise start service using following command: # service snmpd start

Make sure snmpd service starts automatically, when linux comes us (add snmpd service): # chkconfig --add snmpd

Step # 3 : Make sure snmp server configured properly Run snmpwalk utility to request for tree of information about network entity. In simple words query snmp server for your IP address (assigned to eth0, eth1, lo etc): # snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1 ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.0.3 = 2

If you can see your IP address then please proceed to step 4; else it is a time to configure snmp server as follows (by default RHEL and RH 8/9 are not configured for snmp server for security reason):

Configure SNMP (1) Edit file /etc/snmp/snmpd.conf using text editor: # vi /etc/snmp/snmpd.conf

Change/Modify line(s) as follows: Find following Line: com2sec notConfigUser

default

public

Replace with (make sure you replace 192.168.0.0/24 replace with your network IPs) following lines: com2sec local localhost com2sec mynetwork 192.168.0.0/24

public public

Scroll down bit and change: Find Lines: group group

notConfigGroup v1 notConfigGroup v2c

notConfigUser notConfigUser

Replace with: group group group group group group

MyRWGroup MyRWGroup MyRWGroup MyROGroup MyROGroup MyROGroup

v1 v2c usm v1 v2c usm

local local local mynetwork mynetwork mynetwork

Again scroll down bit and locate following line:

Find line: view

systemview

included

system

Replace with: view all

included

.1

80

Again scroll down bit and change: Find line: access

notConfigGroup ""

any

noauth

exact

systemview none none

Replace with: access MyROGroup "" access MyRWGroup ""

any any

noauth noauth

exact exact

all all

none all

none none

Scroll down bit and change: Find lines: syslocation Unknown (edit /etc/snmp/snmpd.conf) syscontact Root (configure /etc/snmp/snmp.local.conf)

Replace with (make sure you supply appropriate values): syslocation Linux (RH3_UP2), Home Linux Router. syscontact Vivek G Gite

For your convenient, here is my /etc/snmp/snmpd.conf file. Feel free to use this file. Make sure you make backup of your existing file if you use this file as it is. Start your snmp server and test it: (a) Make sure when linux comes up snmpd always starts: # chkconfig snmpd on

(b) Make sure service start whenever Linux comes up (after reboot): # service snmpd start

(c) Finally test your snmp server: # snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex

Step # 4 : Install mrtg if not installed Mrtg software may install during initial installation; you can verify if MRTG installed or not with following RPM command: rpm -qa | grep mrtg

If mrtg already installed please see step # 5; else use rpmfind.net to find MRTG rpm or up2date command to install MRTG software: # up2date -v -i mrtg

Fedora Linux user can use yum command as follows to install MRTG: # yum install mrtg

Step # 5 : Commands to Configure mrtg (a) Create document root to store mrtg graphs/html pages: # mkdir -p /var/www/html/mymrtg/

(b) Run any one of the following cfgmaker command to create mrtg configuration file: #cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg.cfg public@localhost

OR (make sure your FQDN resolves, in following example i'm using rh9.test.com which is my router FQDN address) # cfgmaker --global 'WorkDir: /var/www/html/mymrtg' --output /etc/mrtg/mymrtg1.cfg [email protected]

(c) Create default index page for your MRTG configuration: # indexmaker --output=/var/www/html/mymrtg/index.html /etc/mrtg/mymrtg.cfg

(d) Copy all tiny png files to your mrtg path: # cp -av /var/www/html/mrtg/*.png /var/www/html/mymrtg/

Step # 6 First test run of mrtg (a) Run mrtg command from command line with your configuration file: # mrtg /etc/mrtg/mymrtg.cfg

Note: You may get few warning message for first time; ignore them. (b) Fire your favorite web browser (like FireFox :D ) and type url http://www.your.com/mymrtg/ or http://your-ip/mymrtg/

Step # 7 Create crontab entry so that mrtg graph / images get generated every 5 minutes

(a) Login as a root user or login as a mrtg user and type following command: # crontab -e

(b) Add mrtg cron job entry to configuration file (append following line to it): */5 * * * * /usr/bin/mrtg /etc/mrtg/mymrtg.cfg --logging /var/log/mrtg.log

Save file and you are done with MRTG config issues :)

Step # 8 Block ports 161 & 162 at firewall You do not want to give access to everyone to your snmp server for security reasons. SNMP server uses UDP 161, 162 ports for communication. Use Linux IPTABLES firewall to restrict access to SNMP server (a) Allow outgoing SNMP server request from your Linux computer. This is useful when you query remote host/router (replace SERVER IO with your real IP): SERVER="xxx.xxx.xxx.xxx" iptables -A OUTPUT -p udp -s $SERVER --sport 1024:65535 -d 0/0 --dport 161:162 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p udp -s 0/0 --sport 161:162 -d $SERVER --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

(b )Allow incoming SNMP client request via iptables. This is useful when you wish to accept queries for rest of the world (replace SERVER IP with your real IP): SERVER="xxx.xxx.xxx.xxx" iptables -A INPUT -p udp -s 0/0 --sport 1024:65535 -d $SERVER --dport 161:162 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -p udp -s $SERVER --sport 161:162 -d 0/0 --dport 1024:65535 -m state --state ESTABLISHED -j ACCEPT

Pleae note that above two are just SNMP specific iptables rules. Please consult iptables(8) man page for complete information on iptables

Step # 9 Optional: Protect your MRTG graphs/html pages with password protected directory Once again, you would like to restrict access to your MRTG reports. This can easily accomplished with Apache webserver's .htaccess file. If you are on webhosting server with control panel (such as ensim or plesk) then you can use control panel itself to create password-protected directory. Below is process outlined to protect graphs using apache's .htaccess file and htpasswd command: Step # 1: Create .htaccess file in /var/www/html/mymrtg/ directory (add text as follows): vi /var/www/html/mymrtg/.htaccess

Add following text to file: AuthName "MRTG Graphs/Html restricted access"

AuthType Basic AuthUserFile /var/members/.htpasswd require user mrtgadmin

Step # 2: Create a user and password name (-c assumes first time you are using .htpasswd file): # htpasswd -c /var/members/.htpasswd mrtgadmin

For more information please see Apache Webserver Authentication and access control mini-howto.

MRTG: References and further reading Use following resources to find out more Linux help, links to general information and help for MRTG, snmp under Linux/UNIX/Windows OSes: • • • • • • • •

MRTG home page: http://people.ee.ethz.ch/~oetiker/webtools/mrtg/ SNMP home page: http://net-snmp.sourceforge.net/ MRTG authors installation by compiling source code: http://people.ee.ethz.ch/~oetiker/webtools/mrtg/mrtg-unix-guide.html SNMP How-to: http://www.rescomp.berkeley.edu/about/training/senior/progs/SNMPHOWTO/SNMP-HOWTO.html Linux (UNIX) Man pages : snmpd.conf(5), snmpwalk(1), cfgmaker(1), indexmaker(1), mrtg(1), rpm(8), crontab(1) Other MRTG tutorial: Links to tons of mrtg config docs & tutorial Special Case: MRTG Red hat enterprise Linux Virtuozzo VPS configuration See Recommend books for SNMP & MRTG

roblem with MRTG configuration issues When you come across a problem with MRTG and SNMP configurations, I would like to hear about it. You can send all your questions regarding snmp and mrtg configuration, problem to nixCraft forum for further discussion. Well it is true that MRTG is for network monitoring and it can be use to see how much traffic your server/router or ADSL router actually generated, however it will not tell you how much megabytes or gigabytes the daily traffic was. For all such home user and people having dedicated single Linux box hosted somewhere remote at IDC/ISP there is a tool called vnStat (see image below), see Special configuration: Keeping a log of daily network traffic for ADSL or dedicated remote Linux box vnstat - Display traffic for days

vnstat - Displays traffic for each months: