DSL NAT problems, take 3 (pppd[1770]: Couldn't increase MTU to 1500)
Hi there.
In several ocations, my router has suddenly stoped NATing properly: when
the PC's in my LAN try to connect to an Internet host the programs will
just wait a connection in vain, without error or timeout...
The router has Debian Sarge, kernel 2.4.26-1, pppoe_3.5-4.
I can't say what triggers the malfunction: updating or whatever, but has
previously two times (first in august, IIRC). The first time the
problem dissapeared after a couple of days. The next time I tried many
things to solve it. The only clue was a message from pppd when connecting:
Sep 24 19:45:48 severo pppd[1770]: Couldn't increase MTU to 1500
So far I had not touched the MTU; I tried with
pty "/usr/sbin/pppoe -I eth1 -T 80 -m 1452"
and
pty "/usr/sbin/pppoe -I eth1 -T 80 -m 1412"
in /etc/ppp/peers/dsl-provider. Tried blanking iptables filters,
pppoeconfig like mad, and other bizarre things, to no avail. Until I
decided to comment out:
#plugin rp-pppoe.so eth0
and then all worked perfectly! Don't ask me why, since I'm for sure
using PPPoE. But disabling the PPPoE plugin got my router on the road
again.
Well, it happened again about a week ago. The plugin line was
uncommented (on an update?), so I commented it again, but now when I
"pon dsl-provider" without the plugin the PPP data appears on the
screen, and of course there is no connection. The squid proxy does
alleviate part of the problem: the lanners can browse and use programs
with http proxiing, but everything else just hangs indefinitely without
connecting.
I have not found much info about the "Couldn't increase MTU to 1500"
message on the net, and there's nothing related to my case. Any hints
would be appreciated.
Thanks in advance.
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