pppoe MTU fedora core2

sonik.bhoom · 03-21-2005, 03:27 PM

I'll give some quick background.

DSL pppoe modem -> netgear 4 port switch -> Netscreen 5GT & FC2 NAT box

NAT box: FC2
dual 2000+ athlon w1GB RAM, 2NICs being used.

LAN:
netgear 4 port switch, Aopen 8 port switch, linksys WiFi 802.11b AP

I get crap speed out (12-33 kBps --- to 0 after a while on most sites) of any machine connected through the FC2 nat box. I think that it is MTU/MRU related, so i add the following options to /etc/ppp/options:

Code:

mru 1452
mtu 1452

reconnect... ifdown ifcfg-ppp0; sleep 3; ifup ifcfg-ppp0

but when i check the process... mru mtu still set to 1492?

Code:

root     16803 16770  0 14:44 ?        00:00:00 /usr/sbin/pppd pty /usr/sbin/pppoe -p 
/var/run/pppoe-adsl.pid.pppoe -I eth1 -T 80 -U  -m 1412    ipparam sympatico_ca 
linkname ppp0 noipdefault noauth default-asyncmap defaultroute hide-password 
nodetach usepeerdns mtu 1492 mru 1492 noaccomp noccp nobsdcomp nodeflate 
nopcomp novj novjccomp user [usernamedeleted -sb] lcp-echo-interval 20 
lcp-echo-failure 3

then I added MTU=1452, MRU=1452 to /etc/sysconfig/network-scripts/ifcfg-ppp0 but the same effect is seen.

Any ideas?

I'm fresh out...

sonik.bhoom · 03-21-2005, 10:29 PM

Seems one of the ports on my Aopen switch is bad. Changed cables to the NAT box LAN side and everything worked normally suddenly. Total red-herring ....

BTW everything I found seems to indicate that 1492 MTU on a pppoe interface is "EXCATLY WHAT YOU WANT" and that is why you can't change it... :-)

CLAMPMSS is what you really want to change. ( in /etc/sysconfig/network-scripts/ifcfg-ppp0 )

and you know someone this morning even said, "Have you checked the cables?" grrrr. frikin' 'wiggle-the-wires' solution... ;(