[Ham-Computers] RE: Routers, port forwarding and "BitTorrent", questions

Mon Jul 10 20:28:18 EDT 2006

Thank you Aaron,

My router is a LinkSys BEFSR41 V3 with 1.04.12 firmware.  I presently have 3 
BitTorrents downloading and I don't want to make any changes until they're 
finished.  Then I'll go through and set up the IP addresses etc.  Also, TWO 
of the BitTorrents are downloading at significantly faster rates than I've 
typically been seeing, so I still kind of suspect that the"slow" problems my 
be at the peers I'm connected to.

After these half dozen or so Torrents I probably won't be using BT a lot 
anyway as 'most' of the OTR (Old Time Radio programs) that I'm interested in 
is on conventional serviers.  For 'some' reason somebody put a LOT of the 
BBC serials (Journey into Space, Dr Who, etc) on BitTorrents rather than 
conventional sites.3

Again, thank yoiu es 73 de Phil  KO6BB

Phil,

See responses "in-line"...

>>> You wrote:
When I disable the DHCP Server my wife's machine on the same router is
no longer able to connect to the Internet or check her mail (POP account
using O.E).  I have to re-enable the server to get her back on line, at
which time my BitTorrent downloads drop to less than 1KB/s and NO
BitTorrent uploads takes place, presumably due to no Port Forwarding.

1.  Is there a way to allow BOTH machines to connect to the Internet
when I have DHCP disabled, or is that what is actually used to tie the
two machines together?

>>> My reply:
When DHCP is enabled, the router hands out an IP address to all the
computers on your network that requests a DHCP address.  When you
configured your machine for Bit-Torrent, the instructions probably told
you to configure a "static" IP address on your computer (and to turn off
DHCP on your router).  Your computer now still works on the network as
it has a "permanent" address, but your wife's system is down because it
can't get an IP address.  Two solutions:

a)  Assign a static address to your wife's system just like you did
yours.  Change the last octet (the 4th of the 4 "dot" numbers, aka the
"xxx" in 192.168.1.xxx) to something different than any other device on
your network.  For example, if your router is 192.168.1.1 and your
computer is 192.168.1.2, then make your wife's computer 192.168.1.3.

b)  Turn on DHCP on your router and configure it to only hand out a
range of IP addresses that excludes the address your computer is using.
This will prevent the router from handing out an address that conflicts
with your computer's address.  For example, if you're router is .1 and
yours is .2, then configure the router's DHCP server to hand out IP
address in the range of .11 to .20.  This will allow your computer to
work on .1 and any other computers on your network that request a DHCP
address will receive something from .11 to .20.  Note that you can then
also statically assign an IP address to any computer so long that it
doesn't conflict with the range the DHCP server gives out.

Method "b" is more flexible as it allows you to assign static IP's to
those machines that need it while machines to don't "require" a static
address will get a DHCP address.  BTW, this is the way most "large"
networks are done...servers (including printers) are "static" while
clients/workstations are DHCP.  For reference, the most flexibility
comes from "sticky" DHCP where the DHCP server is configured to always
assign a specific computer a specific IP address.  Some Linksys routers
can do this with 3rd party firmware.  It does this based on the
computer's "MAC" address...topic for another discussion.

>>> You wrote:
2.  Am I opening my machine up to "attacks" by using the "Port
Forwarding" feature of the LinkSys router and forwarding the ports used
by BitTorrent (Zone Alarm is still scanning the files as I see the
activity indicator in the task bar lighting up)?  Just to be safe I also
intend to scan EVERY file with the Zone Alarm scanner before opening
them after the download.

>>> My reply:
Opening up ports is always risky.  How much risk depends on the balance
of what you want to get done vs the security risk involved.  The ports
you opened are forwarded specifically to your computer's IP address, so
just your computer is at risk.  The BitTorrent client software is
handling traffic on these ports on your computer, so any risk is
dependent on how well the client software is written and whether or not
anyone's found a flaw or "exploit" that can be used.  You're doing your
best to prevent any possible problem, but, as always, the hackers are
also doing their best to find exploits.  Make sure to keep your client
software up-to-date, esp. if an exploit is found and patched.  I think
you'll find that most BT client software is much safer than the content
most people download...

>>> You wrote:
By the way, BitTorrent is VERY SLOW (< 1KB/s to a max of about 18 KB/s)
compared to regular downloads from Internet servers (I'm on DSL).  My
BitTorrent Upload speeds are usually MUCH faster.  I suspect that this
is due to slow connections that many of the "peers" have (BitTorrent is
a Peer to Peer file sharer and a user can set maximum download/upload
speeds, I have no limits set on mine).  The advantage is that it can
download very large files from many different sources simultaneously and
as the number of "connections" (peers and/or seeds) goes up my download
speed goes up.

>>> My reply:
Many SOHO routers (like the popular Linksys, D-Link, and Netgear
routers) were not designed with BT in mind.  In fact, it's well
documented that BT "breaks" many routers causing router crashes,
lock-ups, and/or reboots...they just weren't designed to handle that
much traffic at one time.  LAN traffic (through the local switch) is
fine, but when you increase the duty-cycle of the LAN-to-WAN portion of
the router, it puts a huge strain on the router's CPU.  SOHO routers
were designed for "lite" use.  But with the advent of BT, these poor
things are dying under stress!  Add to that the crappy firmware that
many of these routers have and you've just run into problems galore!
All's not lost, however...

Which Linksys router do you have?  If it's a WRT54G or WRT54GS (versions
1 through 4), you can use 3rd party firmware that adds features and
increases router stability.  Newer versions of these routers (after
hardware version 5) no longer support 3rd party firmware as Linksys
changed the base OS from Linux to VxWorks.  However, if you have one of
the older units (or the new WRT54GL), I highly suggest that you use
Thibor's HyperWRT firmware.  There is other 3rd party firmware
available, but Thibor's is the easiest to use and quite stable.  More
info here:

http://www.thibor.co.uk/

Also, check this website for great info on Linksys routers in general
(including info, links, and download links for 3rd party firmware):

http://www.linksysinfo.org

With luck, you should be able to BT at faster rates than what you're
seeing.  Hopefully, at worst, you're just seeing BT bandwidth problems
and not hardware based problems (older router that can't handle BT).

73,

  - Aaron Hsu, NN6O

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