Understanding NAT Issues.

In Maximizing Upload/Downloads Success I outlined a procedure which includes a provision for people who are having problems

sharing files with others (specifically people on hosts which are using NAT.) I can see by the responses from one of the

more knowlegable users (you know who you are) that there is some confusion over the problem my suggestions were intended to

address.

This thread is being started to clarify these issues for anyone interested in some ofthe challenges facing users who wish to

share files on Gnutella but can't seem to get it to work correctly.

I recommend that you read this post carefully and make an effort to clearly understand the problem before posting counter

productive comments.

My intent is to make sure that the comments posted to this thread add to the value of the conversation. This discussion seeks

to addess this issue technically.

Recommendation #1 Understand your connection to the Internet. You can go to the following site and look at the various

broadband implementations:

http://www.dslreports.com/pictures

Your connection to the Internet will fall under one of these categories the problems you are likely to have will be related

to your connection.

Recommendation#2 Most firewall issues can be address by LimeWire and most p2p application that support push request. This

usually works unless both users are behind firewalls.


Recommendation#3 Learn a little about the problem / Technology

For general information on how gnutella based applications work (ping, pong query, queryhits, http get and push requests.)

Goto the following site and view the flash presentation great resource for non-techies.

http://www.toadnode.com/site_how_toa...ilx?idVisitor={0917DC6F-6B2A-4B6C-8CE1-15832277C0C5}

Now, for the issue of NAT and forcing the IP. If you don't know what NAT is, or how it works, you can find a complete

overview of the technology here:

http://www.howstuffworks.com/nat.htm


User Issue: "I get lots of hits on my files but no downloads, is something wrong?"

Yes, if your using NAT.

The basic problem with NAT and p2p based application is this:

Your messages can make it onto the network because NAT does the translation between your machine and the machines you are

talking to. (Which means you can search and even download from other people without a problem.) If you can connect, search

and download you don't have to worry about port forwarding or anything of that nature as these activities prove that you can

talk to the network.

Remember this issue we are attempting to address is being able to send or have files uploaded from our/ your computer onto

the network.

When you are using a p2p application that application reads the IP address from the machine it is installed on. Now if the IP

happens to be a NAT Address (192.168.*.* or 10.*.*.* most likely) it inserts this IP into the QueryHit messages and even the

Pong Messages (This happens at the application level NOT the network level.)

Any communications with a NAT based host on the Gnutella network will result in the messages from that machine containing the

NAT address in the Pong message and the QueryHit messages. When someone clicks on these results in their favorite p2p

application it will first attempt to contact the host ip embedded in the queryhit message (which happens to be a private net

ip.)

Private Net Ip address cannot be routed over the public Internet please see: http://www.faqs.org/rfcs/rfc1918.htm for more

information on private network addresses.

When this fails it immediately attempts to send a PUSH request to the host that originally sent queryhit but this fails

because the host just before the original sender cannot communicate with a Private NET IP so the message is dropped (These

are all application level communication failures.)

So how do you fix this? Force the IP or binding in the Application this causes the correct IP to be embedded in the messages

leaving your p2p application. By default most p2p applications assume that you have a public net IP address and this option

is not configured by default.

These issues are not new ones but very old ones to anyone that's been around a while.

http://www.oreillynet.com/cs/weblog/view/wlg/317

Read the sections on experiments and results from the following article.

http://www.firstmonday.org/issues/is...dar/index.html



Hope this helps to clarify the issue or confuse you a little more :-)

__________________
Lee Evans, President
LeeWare Development
http://www.leeware.com

Lee, at the risk of embarrassing myself, gnutella is still telling me that it thinks I'm behind a firewall.

Backgroiund: I'm a newbie (4 weeks) and visit the newbie forum a lot. There is nothing there that I can find pertaining to this problem. That's how I ended up here.

This is a stand-alone computer. I have a cable modem and a new router(LinksysBEFSR41). I connect to TimeWarner RoadRunner, which issues dynamic IPs. I'm running a full default installation of RedHat 7.3 Linux. I have not setup a firewall explicitly. I don't know if the install set one up or not.

I have read this post several times, along with reading all the links several times. A lot of it is over my head, but, due to your excellent explanations, Inow have a good grip on what is happeniing.

As far as I know, I haven't changed anything in the router, which, from what I understand is where you would determine if you're using NAT. I couldn't find anything about NAT in the router setup screens.

In one of your other postings, you mention to go to a site and check what my IP is. In this post, you mention

<So how do you fix this? Force the IP or binding in the Application>

I'm presuming you mean to go into gnutella and enter the IP that I received from the site (66.26.88.140) into the box and click on 'force IP'.

And, from what I understand from your post, this is all that I should need to do. Just above where I entered the IP in gnutella, it confirms that I entered everything correctly. It states that my current IP settings (addressort) as 66.26.88.140:6346.

OK, this is where I might embarrass myself... I did that, and gnutella still says that it thinks I'm behind a firewall.

Also, what happens when my ISP changes my IP address? This happens about weekly.

I just reread your post one more time to make sure I wasn't missing something.

Of course, I AM missing something. I just don't know what. Do I have to stop/restart the gnutella? Do I have to wait a certain amount of time?

Any help you or anyone else can provide will be apreciated.

I think that you raise very valid questions. But first I'll start with some questions of my own. When and how is gnutella (Limewire) indicating that you are behind a firewall?

I do know that when you connect, it might tell you that you are a shielded leaf node. Which simply means that there's another computer aggregating your connection to the network. This is normal.
I'll assume that you are not talking about this message.

Regarding your router LinksysBEFSR41 I believe and I could be wrong that by default this device has DHCP enabled which means that your linux machine as a private net ip address (192.168.x.x or 10.x.x.x) You can verify this by opening a terminal on your linux machine and typing:

ifconfig

and look at your inet addr:

Is the ip of your machine a on a private net?
if yes (good) we're on the right track Because you are using NAT.

Regarding your default Linux installation. I think and again, I could be wrong, but by default Linux will install with your firewall set to medium. I think the choices are (no/medium/high/custom). If I'm correct and the firewall on your linux machine is medium this should not affect your filesharing abilities as the medium setting blocks inbound ports below 1023.

You can verify your firewall settings by using your gui interface /system settings/security levels

The changes that you made in Limewire should do it.

Regarding what happens when your isp changes your ip address. Unless something has changed in LimeWire since I last used it. I don't think the network supports: ip-id-config (term I made up to describe the process of determing the hosts ip and then configing the client with its public ip
address.) The logic being:

/* the client starts up and if the local ip is private-net then send a special message to a configuration server. */

{
client-x-ip-nat --> nat-router-public-ip --> ip-id-config-server
}

/* the server receives the configuration request from the client with public-ip-x i.e. NAT router. and then sends a response to the client indicating the client should force this ip in its configuration or automatically sets-it.- The nat router will forward this request back to the client because it knows that this returning information is in response to a client solicitation */

{
set-client-x-ip-to-public-ip --> nat-router-public-ip-->client-x-config
}

This would be an ideal situation -but is not the case.

So, you'll have to change it in Limewire to match your public ip.

I think that once you apply the changes they become active without you having to reset. However I think it might be a good idea to restart the application or at least disconnect/reconnect to the network. The reason I would make this recommendation is this. Again. unless something has changed (and I don't think a lot has.) Your machine sends to the network a list of the files you are sharing along with your ip address information.

I hope that this information helps you. If you need further assistance please stop by my website and email me directly for more information.

I should note that the worse that can happen is,
you'll be able to search and download stuff and your machine will return queryhits but no one will be able to download from you.

Hope this helps.

__________________
Lee Evans, President
LeeWare Development
http://www.leeware.com

Lee, Thanks for replying.

I'm using gnutella, not Limewire. Don't know that it makes a difference.

Gnutella has a little icon in the bottom right of the screen that is lit red. When you put the cursor on it, it says that I'm behind a firewall.

I did check, and RedHat set it on medium.

You hit the nail on the head. ifconfig shows exactly what you said it would. My internal network shows 192.168..x..x

I did shut down gnutella. When that didn't have any affect, I shut down the computer, unplugged the router and modem. Didn't solve anything.

Also, from what I think you're saying, everytime my ISP changes my IP, I have to find out what it is and put that in the force IP box?

The problem with that is that I won't know when my IP changes.

Oh well, I would love to hear from anyone that has had this problem with gnutella and has solved it. I did find something on one of the forums but the answer comprised of about 20 steps of compiling this and that, with different libs, etc. Seemed like an overkill to me. Besides I don't want to have to become an auto mehcnic just so I can drive a car. I want to use Linux as a tool, something that I have used windoz for, since it came out.

Lee, I haven't emailed you privately because I don't want to impose on your time. I'll look around some more and try different things, and who knows, with all the learning I'm doing, I might just solve this problem.

Thanks

J. Jordan, your welcome.

There are several versions of peer to peer programs for Linux and I simply assumed that because you posted in the Limewire form you were probably using the cross platform version of a Limewire.

Regarding your use of Linux, I started using Linux approximately two weeks ago and found to be very stable and modular system. Contrary to popular belief I've also been able to get a lot of the stability out of windows based platforms. So far I've been able to use my Linux systems for 80 to 85% of the things that typically do in Windows. Linux is a very good operating system but is not for everyone.

Thank you for being so kind and considerate regarding sending me e-mails--it's a rare quality. However, I openly invite people to e-mail me directly because sometimes people wish to share information about thie configurations that they may not want posted on the forum.

Anyway, I wish you luck in your quest to find a solution to your problem.

__________________
Lee Evans, President
LeeWare Development
http://www.leeware.com

test ip test

I am trying to share my files but limewire is saying that I am behind a router or firewall. It notifies me of this where the direct connect on the search tab is. I am currently running limewire on two computers one with windows xp and one with windows ME. They are on a dlink 614+ router. I am not able to browse host between the two computers but I am able to search for specific songs and download between machines. I am getting plenty of hits but no uploads. Can any help. I have read may post and changed to a static IP and configure port forwarding I think. Any other suggestions or reasons why I am still not able to direct connect?

I have the public ip ***.***.***.***. But still there is not a single upload. some files got 100000 hits but 0/0 download.

What could be the reason for it?

Sleepless edit: If you need someone to check your shares, please do so through private message or the likes. Publicly displaying your IP isn't a good idea.


________________________________________
Edited to comply with the House Rules.
Do not divulge anyone's personal information in the forum, not even your own.