Axis Communications - Network Video Support

Technical Note: Change the MTU in Axis network video products

The information in this article applies to:

AXIS 2100/2120/2400/2401/2420 from F/W version 2.12 and AXIS 2400+/2401+ from F/W version 3.01.

Summary

This article shows how to change the Maximum Transmission Unit

The maximum transmission unit is a link layer restriction on the maximum number of bytes of data in a single transmission (i.e.. frame, cell, packet, depending on the terminology).
The below table shows some typical values for MTUs, taken from RFC-1191:

MTU	Where Commonly Used
65535	Hyperchannel
17914	16 Mbit/sec token ring
8166	Token Bus (IEEE 802.4)
4464	4 Mbit/sec token ring (IEEE 802.5)
1500	Ethernet
1500	PPP (typical; can vary widely)
576	X.25 Networks

More information

The MTU is changed in the Camera by creating a file with the new MTU setting, storing this file and execute it at power on by the /etc/inittab.

Example

Create a file with the following content:

#!/bin/sh
ifconfig eth0 mtu nnnnn

where nnnnn is the desired MTU value.
Save the file as mtu

Start a command prompt and change to the directory where the mtu file was saved.
Open an ftp session towards your camera and type the command viewed in bold below:
C:\Axis >ftp <ip address of camera>
Connected to <ip address of camera>
220 Axis 2100 Network Camera 2.12 Feb 05 2001 ready.
User (<ip address of camera>:(none)): root
331 User name okay, need password.
Password: pass (if not changed from default)
230 User logged in, proceed.
ftp> ascii
200 Command okay.
ftp> cd /etc/httpd/html
250 Command successful.
ftp> put mtu
200 Command okay.
150 Opening data connection.
226 Transfer complete.
ftp: 32 bytes sent in 0,00Seconds 32000,00Kbytes/sec.
ftp> quote
Command line to send SITE CHMOD 744 mtu
200 Command okay.

Get the /etc/inittab file from the Camera:
ftp> cd /etc
ftp> get inittab
200 Command okay.
150 Opening data connection.
226 Transfer complete.
ftp: 1380 bytes received in 0,01Seconds 138,00Kbytes/sec.

At this stage, open the downloaded inittab file in an editor and add the following line at the bottom:

mtu:3:once:/etc/httpd/html/mtu

Go back to the ftp session and continue:
ftp> put inittab
200 Command okay.
150 Opening data connection.
226 Transfer complete.
ftp: 1414 bytes sent in 0,00Seconds 1414000,00Kbytes/sec.
250 Command successful.
ftp> by
221 Goodbye.

Restart the Camera and the changes should take affect.

Axis does not take any responsibility for how these configuration changes may affect your system. If the modification fails or if you get other unexpected results, you may have to restore the factory default settings as described in the User’s Manual.