Feb 09 2010

Display Network Stats on Linux with Iptables

Published by at 11:42 am under Linux

As for any firewall, iptables is able to do network statistics reporting. the -v (–verbose) option along with the list switch (-L) show packets and bytes counters.
Network stats are available on a per rule basis. Here is an example on the INPUT chain:
 

[stats@linux_server]$ sudo iptables -nvL INPUT
Chain INPUT (policy DROP 74941 packets, 7900K bytes)
 pkts bytes target prot opt in out source    destination
1392K  543M ACCEPT all  --  lo *   0.0.0.0/0 0.0.0.0/0
1179K  680M ACCEPT all  --  *  *   0.0.0.0/0 0.0.0.0/0   state RELATED,ESTABLISHED
   10   524 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:22
   25  1200 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:21
 5372  260K ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:80
 5842  280K ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:3306 /* Mysql */
   97  4536 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:9999 /* APP */
    0     0 ACCEPT udp  --  *  *   0.0.0.0/0 0.0.0.0/0   udp dpt:69 /* TFTP */
    0     0 ACCEPT udp  --  *  *   0.0.0.0/0 0.0.0.0/0   udp dpt:161 /* SNMP requests */
   73  4380 ACCEPT icmp --  *  *   0.0.0.0/0 0.0.0.0/0   icmp type 8

 
In this example, you could split the RELATED and ESTABLISHED state rule by port to get more detailed numbers.

There is no need to restart iptables to reset packet and byte counters, the built-in -Z or –zero flag makes it for you:
 

[stats@linux_server]$ sudo iptables -Z INPUT
[stats@linux_server]$ sudo iptables -nvL INPUT
Chain INPUT (policy DROP 74945 packets, 7901K bytes)
 pkts bytes target prot opt in out source    destination
    0     0 ACCEPT all  --  lo *   0.0.0.0/0 0.0.0.0/0
    7   436 ACCEPT all  --  *  *   0.0.0.0/0 0.0.0.0/0   state RELATED,ESTABLISHED
    0     0 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:22
    0     0 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:21
    0     0 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:80
    0     0 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:3306 /* Mysql */
    0     0 ACCEPT tcp  --  *  *   0.0.0.0/0 0.0.0.0/0   state NEW tcp dpt:9999 /* APP */
    0     0 ACCEPT udp  --  *  *   0.0.0.0/0 0.0.0.0/0   udp dpt:69 /* TFTP */
    0     0 ACCEPT udp  --  *  *   0.0.0.0/0 0.0.0.0/0   udp dpt:161 /* SNMP requests */
    0     0 ACCEPT icmp --  *  *   0.0.0.0/0 0.0.0.0/0   icmp type 8

 
On top of doing its firewall job and, even if you don’t make use of it, iptables may help you identify more precisely the root cause of network traffic congestion or simply get network stats of what’s going in and out of your servers.


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