[ale] MTU's and DSL's

[Stephan Uphoff]

On Wed, 2005-04-20 at 12:52, James P. Kinney III wrote:
> Does NAT impose some MTU changes? I just had to set the MTU on a web
> server down to 768 to get the traffic passing back out the firewall and
> up a Speakeasy DSL line.


My PPPoE software (FreeBSD) allows the following option:

[tcp]mssfixup
  Default: Enabled.  This option tells ppp to adjust TCP SYN pack-
  ets so that the maximum receive segment size is not greater than
  the amount allowed by the interface MTU.

Do you have PATH MTU discovery enabled?
( Take a look if the packets have DF set)


Stephan