[H-GEN] mtu = 576 on ppp0

[Robert Brockway]

On Sat, 21 Feb 2004, Mick Howe wrote:

> > And why 576 rather than the usual 1492 for Telstra ADSL lines?
> 576 is what the FAQ states

Are you having a PMTU[1] discovery problem?  With PMTU discovery turned
off we're run with MTUs as high as 1454[2].  ADSL is renowned for
developing PMTU issues, particularly with certain providers...

To disable PMTU discovery:

echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc

Put that in a startup script or figure out how your distro turns if off to
make it a permanent change.

Also watch out for ECN which is characterised by an inability to send
email to some remote sites for no apparent reason while all others work
100%.  Yay.

[1] Path MTU discovery.  This problem is characterised by extensive hair
loss (since you're pulling it all out) until you figure out what is wrong.

[2] This number is mentioned in documentation for Bigpond ADSL and others:
http://adsl.cutw.net/bpa-adsl-docs.html and I've used it successfully to
setup sites.  Higher values could be tested of course.

Rob

-- 
Robert Brockway B.Sc. email: robert at timetraveller.org, zzbrock at uqconnect.net
Linux counter project ID #16440 (http://counter.li.org)
"The earth is but one country and mankind its citizens" -Baha'u'llah