Strange network (scp/sftp) problem. [partly solved]

[ddlucas_jp]

I have Gentoo-2.6.5-r1 running on a R50 Centrino Thinkpad laptop. Everything is working great except for a couple of networking issues.

Here's the deal.

* At home (dhcp through ADSL) -- I can connect to other systems using my web browser and ssh. I can also transfer files to/from other computers using scp and sftp.

* At work (static IP behind a firewall) -- I can connect to local and remote computers using web browsers, telnet, and ssh.

* At work -- I can transfer only SMALL files to/from local and remote computers using scp and sftp. If I try large files (>1MB), then scp and sftp stall.


The only changes I make between home and work are commenting and uncommenting 'iface_eth0=dhcp' in my /etc/conf.d/net file.


It can't be a network card issue because things are okay at home.

Also, it can't be a firewall issue because at work I cannot transfer files to/from another system behind the firewall.

All of my settings in /etc/conf.d/net are standard, as compared to other people running linux at work.


I'm at a loss here. Anyone have any ideas??

[nobspangle]

It could be a compatability between your network card and the hubs/switches you use at work.

[think4urs11]

Hi!

Sounds to be most probably an issue with auto negotiation, especially the duplex settings.

mii-tool and/or ethtool might help here.

HTH
T.
_________________
Nothing is secure / Security is always a trade-off with usability / Do not assume anything / Trust no-one, nothing / Paranoia is your friend / Think for yourself

[ddlucas_jp]

Thanks for the feedback.

Here's my ethernet card from lspci:

Intel Corp. 82801BD PRO/100 VE (MOB) Ethernet Controller (rev 81)


I'm using the e100 driver for this card. I currently have it loaded as a module with the following options in my modules.autoload.d:

e100 ucode=1 flow_control=1 e100_speed_duplex=0


dmesg shows the following output:

e100: no version magic, tainting kernel.
Intel(R) PRO/100 Network Driver - version 2.3.40
Copyright (c) 2004 Intel Corporation

e100: Using specified speed/duplex mode of 0
e100: Using specified ucode value of 1
e100: Using specified flow control value of 1
e100: selftest OK.
e100: eth0: Intel(R) PRO/100 Network Connection


At work, I've tried various combinations of the options for e100, including forced speed and duplex values, and I still have the same 'scp stalled' problem. Also, I was careful to set flow_control=0 when e100_speed_duplex > 0.

[ddlucas_jp]

Thanks again for the tips.

I found ethtool to be a very helpful and efficient tool. I was able to try a variety of different settings very quickly.

I focused on the speed/duplex and Tx/Rx settings. I also change the 'maximum transfer unit' (MTU) setting in ifconfig from 1500 to 576.

The intial scp transfer rates changed between the various cases, but scp always stalled and failed when transfering between two computers at work.


Does anyone have any other helpful tips?

[jftuga]

You could try setting up ftp, rsync, or wget+apache to see if the problem is specifically with sftp/scp or a more general problem.

Or better yet, you can also try the netcat program (nc). Think of it as a network version of cat. You netcat a file across the network. It is a very easy tool to test with.

-John[[/url]

[ddlucas_jp]

On a whim, I plugged in an old pcmcia linksys ethernet card into my brand-spanking-new laptop using the NE2000 (pcnet_cs) driver. I can now upload and download files at work and home.

This also solved a printing problem that I posted awhile back.

(see 'CUPS Printing Problem' posting about 'unable to send trailing nul to printer').



At work, however, scp still stalls out, though ftp works fine. I can live with this for now, but would like to get to the bottom of this.

It's strange that the Intel card works fine at home, but not at work.

[embobo]