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Hi Aviram,

  Well, I strongly believe that playing around with the MTU is not the
right way 
to go about it. As you said, the ppp0 is set 1452 and eth0 is set to
1500. The 
packet filter should be able to fragment the packets correctly. I use a
similar setup
at home, only with a cable modem and an ISDN with another, and I don't
get any
problems.

  However, I have encountered in the past a similar problem. It was
related to 
a transparent proxy issue with my ISP. According to your information, I
would guess
that your ISP is Internet Gold, as these problems are somewhat common
over there.
- From time to time, they add new subnets to the ADSL clients, and they
simply forget
to define all the proper settings in the transparent proxy. 

  I would suggest that you approach your ISP and ask them to put a trace
on your
FTP session, so they can check where it gets cloged up.

Best regards,
  Nir Simionovich
  Senior Network Manager
  m-Wise

http://www.m-wise.com/

Phone:   +972 (9) 958-1711 ext. 105  
Fax:       +972 (9) 958-1739
Mobile:   +972 (54) 482826




- -----Original Message-----
From: Aviram Jenik [mailto:[EMAIL PROTECTED]]
Sent: Monday, March 04, 2002 8:23 PM
To: [EMAIL PROTECTED]
Subject: mtu problems?


A question to the MTU gurus (Muli/Dani?):

I'm pretty sure I have an MTU problem. However, I can't figure out:
A. How to 'debug' it (i.e. I don't know if the problem is really MTU)
B. What the problem is (if it exists).

I think that (A) is especially important, since I'm getting the feeling
I'm
chasing ghosts;

The symptoms are as follows:
I'm have an excellent ADSL connection, but connecting to certain servers
using timeout-sensitive protocols I am having problems. For example,
when
trying to upload files to my FTP server, either using FTP or SSH + rz,
the
connection takes forever and breaks up in the middle quite frequently.
Pinging the server shows that my packet loss is negligible and that the
connection is fast (~35ms, <1% packet loss). Other people can FTP with
no
problems. I have no other problems with that server or with my Internet
connection in general (i.e SMTP, HTTP all work quite nicely). The only
think
I can think of is some strange MTU problem.

For example, trying to FTP from my linux connection (the one connected
to an
ADSL) via FTP fails miserably with timeouts. The connection is done
directly, so it's not a masquerading problem.

Now the facts:
The MTU on the ppp0 interface is: 1452
The MTU on the eth1 interface (the one connected to the ADSL modem) is:
1500

as far as I can tell from the how-to, that should be the right values.
Any
idea how I can debug it and/or fix the problem?

Thanks,
Aviram Jenik
Beyond Security Ltd.
http://www.BeyondSecurity.com
http://www.SecuriTeam.com

Know that you're safe:
http://www.AutomatedScanning.com



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