I have a BSNL DataOne Broadband connection in India and I have it working without any problems on my Ubuntu Linux running on AMD64 (the OS is 32-bit). I have no problems whatsoever connecting to any site on the internet. My ADSL modem is a Huawei MT882.
My company allows people to connect to office from home on a Cisco VPN client (Ver. 4.6.00). I downloaded the Linux version of the client from an internal site, compiled, etc, and am able to connect to my office through VPN. So far so good.
However, when I telnet to my office machine, it invariably hangs when I do even an "ls -al". However, "ls" on a directory with one or two files succeeds. When I tried to connect using the Citrix ICA client, all I get is a blank screen (or sometimes a blob of what should be the login prompt), and there's no way I can connect.
I read on the net that this might be a problem with my MTU setting, and increased the MTU to 2000 using "sudo ifconfig eth0 mtu 2000". SOMETIMES THIS WORKS. I get the ICA client (and telnet too) working, and I can connect to office and work as long as I wish (well, sometimes it disconnects after a couple of hours or so - even the modem's ADSL Link LED stops glowing).
The funny thing is - the success because of changing the MTU is NOT AT ALL REPEATABLE. If it works once, it doesn't mean it'll work again either in 10 mintues or tomorrow. I've tried MTU's all the way from 1100 to 2000, and no value seems to make it work always. Another thing I've observed is - it's *harder* to get it working during the day, and easier early in the morning and late in the evenings. Please note that there's always a "probability" that it connects!
Ubuntu comes with ipv6 enabled by default; I disabled that acting on somebody's advice. That changed NOTHING.
Please help. I've knocked on every door known to man before I came here!