[Soekris] changing mtu size on openbsd problems

[Chris Cappuccio]

Why would you set the MTU on your physical ethernet interface below 1500?

That makes no sense at all.

It would be best to set your physical ethernet mtu above 1500 so that your
pppoe implementation can pass full 1500 byte packets.  But, most ethernet
drivers don't support this...  And whether or not the actual chips do, and
to what maximum frame size they can send or receive, often depends on model
and revision.  In many cases it is not documented at all.

Didier Wiroth [didier.wiroth at mcesr.etat.lu] wrote:
> Hi,
> 
> I've been using my soekris 4801 (latest firmware) box for a few days now with openbsd 3.8 and "kernel" pppoe.
> I used to change the mtu size with ifconfig in my hostname.pppoe0 
> 
> Here  was my hostname.pppoe0 file:
> pppoedev sis2
> !/sbin/ifconfig sis2 up mtu 1440
> !/usr/sbin/spppcontrol \$if myauthproto=pap myauthname=x \
>         myauthkey=y
> !/sbin/ifconfig \$if inet 0.0.0.0 0.0.0.1 netmask 0xffffffff
> !/sbin/route add default 0.0.0.1
> up
> 
> As a result I had strange problems, I was not able able to browse some sites for example: www.ebay.de, www.microsoft.com.
> 
> I had to remove the mtu settings from hostname.pppoe0 and do this with pf:
> scrub out on pppoe0 max-mss 1440
> 
> May be someone experienced the same problems?
> 
> thank you for feedback
> didier
> 
> 
> 
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