some sites unreachable with DSL

some sites unreachable with DSL

Post by Jim » Sat, 26 Jan 2002 22:46:45



I recently upgraded to RedHat 7.2 and am using kernel support to run
PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to reach
certain sites on the Web. If I boot up to Windows on the same machine,
the sites load right away. I have tried tweaking RWIN and MTU, but none
of this has made any difference. Is there anything I can do to zero in on
the problem?
 
 
 

some sites unreachable with DSL

Post by Frank Elsne » Sat, 26 Jan 2002 23:04:12



> I recently upgraded to RedHat 7.2 and am using kernel support to run
> PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to reach
> certain sites on the Web. If I boot up to Windows on the same machine,
> the sites load right away. I have tried tweaking RWIN and MTU, but none
> of this has made any difference. Is there anything I can do to zero in on
> the problem?

From my "/etc/rc.local" on RH 7.2

# Set ECN (Explicit Congestion Notification) with 2.4.x Kernels

echo "0" >/proc/sys/net/ipv4/tcp_ecn

--Frank Elsner

 
 
 

some sites unreachable with DSL

Post by Jim » Sat, 26 Jan 2002 23:42:12


I added the suggested line to /etc/rc.local and rebooted. No change. I
still can't reach the sites.


>> I recently upgraded to RedHat 7.2 and am using kernel support to run
>> PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to reach
>> certain sites on the Web. If I boot up to Windows on the same machine,
>> the sites load right away. I have tried tweaking RWIN and MTU, but none
>> of this has made any difference. Is there anything I can do to zero in
>> on the problem?

> From my "/etc/rc.local" on RH 7.2

> # Set ECN (Explicit Congestion Notification) with 2.4.x Kernels

> echo "0" >/proc/sys/net/ipv4/tcp_ecn

> --Frank Elsner

 
 
 

some sites unreachable with DSL

Post by Hal Burgis » Sat, 26 Jan 2002 23:44:46




Quote:> I added the suggested line to /etc/rc.local and rebooted. No change.
> I still can't reach the sites.

No need to reboot. What do you mean 'tweaking MTU'? It sounds like a
classic Path MTU Discovery problem. Or ECN. MTU on ppp0 should be 1492.
If that doesn't work try even lower settings.

Quote:>>> I recently upgraded to RedHat 7.2 and am using kernel support to run
>>> PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to
>>> reach certain sites on the Web. If I boot up to Windows on the same
>>> machine, the sites load right away. I have tried tweaking RWIN and
>>> MTU, but none of this has made any difference. Is there anything I
>>> can do to zero in on the problem?

--
Hal Burgiss
 
 
 

some sites unreachable with DSL

Post by Karl Heye » Sun, 27 Jan 2002 00:03:23



> I added the suggested line to /etc/rc.local and rebooted. No change. I
> still can't reach the sites.



>>> I recently upgraded to RedHat 7.2 and am using kernel support to run
>>> PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to reach
>>> certain sites on the Web. If I boot up to Windows on the same machine,
>>> the sites load right away. I have tried tweaking RWIN and MTU, but none
>>> of this has made any difference. Is there anything I can do to zero in
>>> on the problem?

>> From my "/etc/rc.local" on RH 7.2

>> # Set ECN (Explicit Congestion Notification) with 2.4.x Kernels

>> echo "0" >/proc/sys/net/ipv4/tcp_ecn

Just to clarify, the above disables ECN.  You can verify that it has
been run with

cat /proc/sys/net/ipv4/tcp_ecn

if 1 is shown then it's still enabled, if 0 then it is disabled.

Can you state which site you are accessing, post the ifconfig output,
you can mask out the IP if that is an issue.

karl.

 
 
 

some sites unreachable with DSL

Post by Jim » Sun, 27 Jan 2002 00:02:03


MTU for ppp0 was already at 1492, so I changed it to 1474. That was it.
All sites are reachable now.

Thanks guys!




>> I added the suggested line to /etc/rc.local and rebooted. No change. I
>> still can't reach the sites.

> No need to reboot. What do you mean 'tweaking MTU'? It sounds like a
> classic Path MTU Discovery problem. Or ECN. MTU on ppp0 should be 1492.
> If that doesn't work try even lower settings.

>>>> I recently upgraded to RedHat 7.2 and am using kernel support to run
>>>> PPPoE with PPP 2.4.1. Since the upgrade, I haven't been able to reach
>>>> certain sites on the Web. If I boot up to Windows on the same
>>>> machine, the sites load right away. I have tried tweaking RWIN and
>>>> MTU, but none of this has made any difference. Is there anything I
>>>> can do to zero in on the problem?

 
 
 

some sites unreachable with DSL

Post by David Efflan » Sun, 27 Jan 2002 11:24:02



> MTU for ppp0 was already at 1492, so I changed it to 1474. That was it.
> All sites are reachable now.

Efficient says they found that 1454 mru for pppoe works best (they set
that instead of mtu), but I am using the default 1492 with Linux.

One other note is that the nic that handles pppoe (not pppoe itself)  
should remain at mtu 1500, but internal nics should be set lower.  Docs
for rp-pppoe suggest 1452 or maybe even 1412 (ie, it is hard to shove a
1500 byte packet through a 1492 or smaller hole).  My LAN nics seem to
work fine at mtu 1452 (just a little tricky to automate that for pcmcia
on my laptop)..

--
David Efflandt - All spam is ignored - http://www.de-srv.com/
http://www.autox.chicago.il.us/  http://www.berniesfloral.net/
http://cgi-help.virtualave.net/  http://hammer.prohosting.com/~cgi-wiz/

 
 
 

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--
Consulting Minister for Consultants, DNRC
The Bill of Rights is paid in Responsibilities - Jean McGuire
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