Help please: How to alter MTU

Help please: How to alter MTU

Post by Jianfeng Wan » Fri, 06 Jul 2001 00:54:34



Hi grus,

We have problem with our ISP and we are not able to send packet size
larger than 800 to internet. The suggested solution is that we alter our
MTU size on our Open-BSD firewall. Do you know how to do this?

TIA

  jeffrey.wang.vcf
< 1K Download
 
 
 

Help please: How to alter MTU

Post by pe.. » Fri, 06 Jul 2001 01:44:47



> This is a multi-part message in MIME format.
> --------------E98705931ACFC88D2F4F691A
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> Hi grus,
> We have problem with our ISP and we are not able to send packet size
> larger than 800 to internet. The suggested solution is that we alter our
> MTU size on our Open-BSD firewall. Do you know how to do this?

normally it's done with ifconfig. The openbsd manpages does not
mention it ( freebsd does). But running strings on ifconfig
does show up something about mtu.

Go ahead and try :
ifconfig xx0 mtu 800

if it doesnt help, well, you got the source ...

peter h

> TIA
> --------------E98705931ACFC88D2F4F691A
> Content-Type: text/x-vcard; charset=us-ascii;
>  name="jeffrey.wang.vcf"
> Content-Transfer-Encoding: 7bit
> Content-Description: Card for Jianfeng Wang
> Content-Disposition: attachment;
>  filename="jeffrey.wang.vcf"
> begin:vcard
> n:Wang;Jianfeng
> tel;work:519 6222300 2873
> x-mozilla-html:FALSE
> url:www.comdev.ca
> org:ComDev Ltd.;MIS
> adr:;;155 Sheldon Drive;Cambridge;Ontario;N1R 7H6;Canada
> version:2.1

> title:Network Administrator, CCNP, CCDA, MCSE
> fn:Jianfeng Wang
> end:vcard
> --------------E98705931ACFC88D2F4F691A--

--
Peter H?kanson        
        IPSec  Sverige      (At the Riverside of Gothenburg, home of Volvo)
           Sorry about my e-mail address, but i'm trying to keep spam out.
           Remove "icke-reklam"and "invalid"  and it works.

 
 
 

Help please: How to alter MTU

Post by Robroy Gre » Fri, 06 Jul 2001 04:34:11


: Go ahead and try :
: ifconfig xx0 mtu 800

: if it doesnt help, well, you got the source ...

Hi!  Just FYI, I tried this on my OpenBSD 2.7 machine and it worked great.

ernest:/home/robroyg# ifconfig tun0 mtu 800
ernest:/home/robroyg# ifconfig -a
lo0: flags=8009<UP,LOOPBACK,MULTICAST> mtu 32972
        inet 127.0.0.1 netmask 0xff000000
lo1: flags=8008<LOOPBACK,MULTICAST> mtu 32972
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        media: Ethernet manual (none)
        inet 10.1.1.10 netmask 0xffffff00 broadcast 10.1.1.255
tun0: flags=11<UP,POINTOPOINT> mtu 800
        inet 165.227.119.248 --> 165.227.1.132 netmask 0xffff0000
enc0: flags=0<> mtu 1536
enc1: flags=0<> mtu 1536
enc2: flags=0<> mtu 1536
enc3: flags=0<> mtu 1536
bridge0: flags=0<> mtu 1500
bridge1: flags=0<> mtu 1500
gre0: flags=8010<POINTOPOINT,MULTICAST> mtu 1450

(The MTU used to be 1500, like you might expect.)

-Robroy Gregg
Santa Cruz, CA  USA

 
 
 

1. Altering MTU values (how to?)

I have two different X86 machines with IBM 16/4 Token Ring network
interfaces.  One boots up with an MTU of 4406 and the other with
1542.

The one with the lower MTU causes packets on our network to be fragmented.
How do I control the MTU of the Token Ring interface under Solaris X86 2.4?

TIA,

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