Change MTU (Maximum Transmission Unit) of network interface
Posted by Admin on October 14th, 2006
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Default MTU Size for Different Network Topology
| Network | MTU(Bytes) |
| 16 Mbit/Sec Token Ring | 17914 |
| 4 Mbits/Sec Token Ring | 4464 |
| FDDI | 4352 |
| Ethernet | 1500 |
| IEEE 802.3/802.2 | 1492 |
| X.25 | 576 |
To change the MTU of an interface on GNU/Linux, you just need to tell ifconfig to do so, like this for example:
#/sbin/ifconfig eth0 mtu 1492
To change it permanently on Debian, put it in the /etc/network/interfaces file .where almost all network parameters are found. To do this, just add a line mtu to the definition of your interface and save the file.
Example
iface eth0 inet static
address 192.168.0.1
network 192.168.0.0
gateway 192.168.0.254
netmask 255.255.255.0
mtu 1492
Warning: the following is mostly obsolete in Debian Sid and Etch
It seems that the dhcp clients are not configured by default to do the same for dynamically assigned configurations . So, you need to use a tweak to achieve the same. We’re going to use the pre-up feature of /etc/network/interfaces like this:
iface eth0 inet dhcp
hostname “mymachine”
name LAN Interface
pre-up /sbin/ifconfig $IFACE mtu 1492
More common Recommended Values
Dial-up Connections - 576 Bytes
PPPoE Broadband Connections - 1492 Bytes
Ethernet, DSL and Cable Broadband Connections - 1500 Bytes
June 4th, 2008 at 11:28 pm
pre-up /sbin/ifconfig $IFACE mtu 1492
You might like using post-up instead.