Am I missing something? (ADSL-MASQing)

Mark Purcell mark at
Tue May 21 20:45:22 EST 2002

Hash: SHA1

On Tue, 21 May 2002 11:10, Neil Symons wrote:
> I've configure my home Ok, and a Business
> However another Business I am helping out cannot seem to Surf Direct nor
> able to finish downloading their first e-mail when popping on all their
> Windoze Boxes behind the router.

Had a similar problem when I first got onto ADSL, napster downloads would 
never finish. And I have heard of others having similar problems trying to 
download largish files.

What ended up solving it was the -m option, which clamps the TCP maximum 
segment size.  The man page for pppoe states that you are strongly 
recommended to use -m 1412 if you have a LAN behind your gateway, which seems 
to fit your case exactly.

> pty "pppoe -I eth1 -T 80"

Mine reads:

pty "pppoe -I eth0 -T 80 -m 1412"

Hope that helps.


       -m MSS Causes pppoe to clamp the TCP maximum segment size at the 
specified value.  Because  of  PPPoE  overhead,
              the  maximum  segment size for PPPoE is smaller than for normal 
Ethernet encapsulation.  This could cause
              problems for machines on a LAN behind a gateway using PPPoE.  If 
you have a LAN behind a gateway, and the
              gateway connects to the Internet using PPPoE, you are strongly 
recommended to use a -m 1412 option.  This
              avoids having to set the MTU on all the hosts on the LAN.
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