Hello everyone,

Troubles again with <subject> ... let me explain the setup first:

LEAF/Bering box on PPPoE line at remote office. ppp0 MTU is 1492 - have
tried overriding in dsl-provider, but to no avail (doesn't do
anything?). ClampMSS is enabled in Shorewall.

Mandrake/Shorewall on regular Ethernet line at main office. 

They communicate using FreeSWAN IPSEC and has a VPN connection running.
I have added "overridemtu=1350" to make sure packet sizes aren't the
problem.

Both firewall have "ACCEPT all all ICMP" as not to give problems with
PMTU discovery.

DNAT is configured, so the external PPPoE interface IP forwards
ssh-requests to an internal host across the VPN transparently. This is
done with SNAT.

Observations:
Pinging from an external IP-address to the PPPoE box works with packet
sizes up to 1492 (ping -s 1464 x.x.x.x), but not with packet sizes over.
I can't figure out why, but I suspect that ping sets the DF flag.

Pinging internally via VPN works fine, no matter packet sizes, due to
"overridemtu" in FreeSWAN.

Doing SCP from external address to the PPPoE firewall works fine (due to
ClampMSS?).

Doing SCP from external address to the PPPoE SNAT port (which is
forwarded to the remote host over VPN) halts, because large packets are
dropped.

HEEEELP! :)

Not being able to ping with large packets from the internet I can live
with. But the SNAT large packets problem I cannot live with.

Hope one of you gurus can help.


-- 
Lars Karlslund <[EMAIL PROTECTED]>
LeiCeps



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