How do I change MTU? HELP

**fizis** · 08-11-2006

HI

How do I change MTU for pppoe to 1412???

pppoe -m 1412

does not work!!!

**Zelmo** · 08-11-2006

You can apply an MTU to your network adapter using ifconfig, like so:

Code:

# ifconfig eth0 mtu 1412

**graysky** · 12-11-2006

How can one make the mtu size permanent such that it always is set to that value when the system reboots? Using debian and an mtu size of 4000.

Thanks!

**Zelmo** · 12-12-2006

If you use a static address, you can set the mtu in /etc/network/interfaces. Under the entry for eth0 (assuming that's the interface you want to set), put a line like this:

Code:

 mtu 1400

**graysky** · 12-12-2006

Any ideas how to do it with dhcp? I found this http://glasnost.beeznest.org/articles/290

but can't make it work with my machine.

**Zelmo** · 12-12-2006

Yeah, the man page for interfaces only mentions the mtu setting being used with static address. The pre-up idea is pretty good; if that isn't working, then try the same thing with post-up.

**graysky** · 12-12-2006

I think my problem is the syntax of the thing.

hostname "mymachine" - I'm assuming "mymachine" is the hostname of the local machine?

name LAN Interface - Is this entered as such or do I need to replace LAN interface with eth0 or something?

pre-up /sbin/ifconfig $IFACE mtu 4000 - Again, assuming I type it as it's shown.

Reference: http://glasnost.beeznest.org/articles/290

**Zelmo** · 12-12-2006

Code:

hostname "mymachine"

will request that your hostname be set to "mymachine" by the DHCP server. I don't know how important it is for your hostname to be set this way, or whether this will even override the already-set hostname. But it doesn't hurt to have this line; just substitute your real hostname, as given when you type the hostname command in a console.

Code:

name LAN Interface

This is a line for which I don't see any explanation in the man page. I'd leave it out (or at least comment it out).

Code:

pre-up /sbin/ifconfig $IFACE mtu 4000

Yes, type this as shown. You can also use your real interface name (such as eth0) in place of the variable $IFACE, and you don't strictly have to specify the full path to ifconfig. For safety, check that ifconfig is really in /sbin.
You can also substitute post-up for pre-up and see if that works. The rest of the line would stay the same.

**graysky** · 12-12-2006

Thanks... I tried just the pre-up line and it didn't work. I just went static and everything is good.

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