Failed Hash Checks

[nyi8083]

I've been using bittorrent for a while now, but have lately been running into a problem that is really annoying. nearly all of my downloads run fine until around 99.9% when there is like 1 piece remaining to download, but this 1 piece will be downloaded many many times due to the piece failing hash checks. i was just wondering if this is something i could fix somewhere in the settings of the client i use (azureus, but i've also run into the problem in ABC) or if its simply something i have to live with. The download will eventually finish, it just ends up taking a lot more time, and bandwidth, than is necessary.
thanks for any help

[Vladd44]

This usually results from NAT routers replacing legitimate data in your packets. When the packet fails the hash check, because the router scrambled it.

There are three ways of fixing the problem:

1) Do not run your router in DMZ mode, many routers seem to employ game mode-like mangling by default for DMZ-bound traffic. Instead, you should enable explicit port-forwarding on your router incoming ports.

2) If your router a Game mode option (many do not, even though they mangle anyway), turn it off.

3) If you have done the above two, then try connecting directly to the internet (i.e. bypass your NAT router entirely) to finish off the last piece.

[nyi8083]

thanks, just changed the settings on my router and the download that had 53 failed hash checks is finally finished

[Vladd44]

np

Your post motivated me to do a page on main site to cover the problem.

http://www.vladd44.com/torrent/hangs.php

ANd while I was at it, I did a few others too.

[MUx]

Hey.. i am having the same kind of problem.. i have this torrent.. that keeps failing hash checks for various pieces.. im using bittornado... do u think u can help me with this??? i'd reallly appreciate it

[Vladd44]

Two Basic Scenarios:

Multiple hash failures on different pieces but eventually get a good copy of each one, then it's the fault of the people sending to you.

Repeated failure on one piece could be caused by a host of reasons. One that you should consider first is where the bad pieces are coming from. Is it one IP?

You also may want to consider another Client, to see if the problem persists or not. http://www.vladd44.com/torrent/clients.php . Azureus is a good alternative that will automatically ban that ip. (If you have checked Options --> Ip Filters --> Enable & Block peers that consistently send bad data).

If that doesnt help, If you are running a router, after verifying that it is properly forwarded, you may want to check and see if your running the most current firmware.