Alicia da Conceicao wrote:
> Greetings:
> 
> For some reason, whenever I attempt to increase the MTU on my in kernel
> pppoe interface beyond 1460, it fails:
> 
>         # ifconfig pppoe0 mtu 1460
>         *OKAY*
>         # ifconfig pppoe0 mtu 1461
>         ifconfig: SIOCSIFMTU: Invalid argument
> 
> Note that pppoe0 is tried to physical ethernet interface fxp0, which
> itself has a MTU of 1500.
> 
> However, other PPPoE implimentations can use MTU values as high as 1492.
> Even the NetBSD PPPoE documentation at:
> 
> 	http://www.netbsd.org/Documentation/network/pppoe/
> 
> uses 1492 as an example MTU value for in kernel PPPoE.
> 
> Any ideas as to why I can't use the higher MTU value for the NetBSD in
> kernel PPPoE?  The reason why this is a problem is that Windows clients
> (running WinXP or Win98SE) behind a NetBSD NAT firewall are unable to
> use Windows Update or down load large files from some websites.  In my
> /etc/ipnat.conf:

Is there some reason why you're blocking the ICMP
type 3 code 4 packets?  See :

http://www.phildev.net/mss/mss-filter.html