SSH Port Forwarding Example


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If you would like to know more about what port forwarding is you can check out my page " Port Forwarding in a Nutshell " Rule 1 on Testing Port Forwarding: This will be the IP I put into the rule. The server connects to a configurated destination port, possibly on a different machine than the SSH server. I added this tool to make setting a static IP as easy as possible for people instead of manually doing it on there systems Which if a person has never done it before can be a little intimidating. So whether you don't understand how to forward ports, or your simply looking for an easier way to forward ports then this program is for you.

What Is SSH Port Forwarding, aka SSH Tunneling?

Port forwarding

Een standaardthuisnetwerk heeft toegang tot internet via een DSL of kabelmodem. De modem kan worden aangesloten op een router, of in de meeste gevallen zit de modem al in de router.

De router wordt vervolgens aangesloten op het lokale netwerk door middel van een ethernetkabel of Wi-Fi. Alleen de router heeft directe toegang tot het internet.

Het IP-adres is dus gekoppeld aan de router en niet aan de achterliggende computers. De computers in het lokale netwerk zijn onzichtbaar voor het internet als ze beschikken over een lokaal IP-adres. Dit gaat meestal via DHCP. Port forwarding is nodig in de router om computers met een intern IP-adres te verbinden met het externe IP-adres van de router. Port forwarding wordt gewoonlijk gedaan op Unixcomputers waar poortnummers genummerd onder alleen geopend kunnen worden door software die draait als rootgebruiker.

Programma's starten als root kan een beveiligingsprobleem opleveren. Een veelvoorkomende oplossing is om een server te laten luisteren listen naar een hoger poortnummer en die via de router om te leiden naar een lager poortnummer. Als men een webserver opzet, gebeurt dat standaard op poort Wanneer de webserver wordt gestart als root kan dit een probleem opleveren voor de veiligheid. Daarom laat men de webserver luisteren op poort Vervolgens wordt de router zo ingesteld dat al het verkeer dat een request doet op poort 80 omgeleid wordt naar poort Reverseport forwarding , of omgekeerde port tunneling, wordt gedaan door twee componenten die aan elkaar gekoppeld worden met als doel een port forwarding.

Dit wordt meestal gerealiseerd door software. I have also found that some home users don't realize they have a firewall installed in the first place. A lot of the antivirus packages out there come with built in firewalls as part of the antivirus. So users think they have antivirus but don't realize it is also a firewall.

So when a warning pops up about a program trying to connect to the net they seem to like to hit block by default, thus breaking things more than helping. I have also helped users who uninstalled their firewall software but it didn't remove properly. So the firewall drivers where left behind and blocked all incoming connections. So the user had to dig in and get them removed before port forwarding would even work.

For a user who doesn't understand how or what a firewall is used for, they should not have one installed if they are behind a router anyways. Remember a router is a hardware based firewall, it blocks incoming connections except those allowed through by the port forwarding rules. In cases like this the only real reason to have a software based firewall installed is to block programs from connecting to the net.

Now this is great for us techs who understand and know what will happen if we block a program. But to many times I have had to go to a customers home and fix their system because the firewall had blocked Windows, their email or something important from even getting on the net. So you can see my frustration with software firewalls for people who don't know how to use them.

With all that being said double check that the firewall you have installed isn't blocking the program or port you need open. The built in Windows firewall can be a pain as well, but normally does not cause the problems that many user installed software firewalls cause.

But never the less, make sure the windows firewall allows either the port or program through as well. If the windows firewall is corrupted or broken this will keep port forwarding from working as well. I helped a user who was not behind any routers, was connected directly to the modem.

No firewall software of any kind installed, heck he didn't even have a antivirus He had one by the time I was done helping him hehe. While looking into his system trying to find out what was blocking the connections I noticed the Windows firewall service was off. When I went to turn it back on it failed. Digging more into it the WMI was corrupted which kept the Windows firewall from working properly. Once I fixed the WMI problem for him the firewall then started working right.

After that his ports all worked fine. The Windows firewall is tied into the system more than some people realize, and even if disabled it can still cause problems. So making sure the Windows firewall is working right makes a very big difference.

This is a page I found showing how to repair WMI http: Here is an example. So now on the port forwarding page of these types of routers you can set which WAN connection the rule is for. So you have to figure out which you need and that's simple: The problem with this is some times they will have your computer name listed multiple times, and each computer name points to a different IP.

So if you choose the wrong one the port forwarding rules won't work. In the Thomson you have to go to the device list and remove the extra entries. The 2wire doesn't give that option, rebooting the routers may help clear the extra entries.

So keep this in mind, I have seen this keep port forwarding from working since the computer name has a different IP than what your computer actually has. Lets say I have a Thomson router, I go to add a port forwarding rule and my computer name shows up 3 times in the device list. Which one do I choose?

Well at that point you need to go to the device list and see what IP each one has. Check what your local IP is and remove the extra ones that don't match. If you can't remove them just make sure to choose the one that points to your correct local IP. Then your port forwarding will be fine at that point. If you choose the wrong one it will be pointing to a different local ip and so of course your port forwarding won't work.

There are some routers such as Linksys, D-Link and many others that do not do any checks if a port is already in another port forwarding rule. So when there are multiples of the same port number the port forwarding rule will not work. As you can see port is in 2 rules. The 1st one points to a different IP than that of the 2nd rule.

So the router will honor the 1st rule and the 2nd port forwarding rule to port fails. By removing the 1st rule the 2nd one will now work. DMZ is a open all ports rule. And on most routers it over rides the port forwarding rules. So if you have DMZ enabled and it isn't pointing to the machine you need the ports open on, then this will create problems. So if your setting up port forwarding rules, make sure DMZ is disabled.

I have found there are also some simple things you can do as well to get things working. Here is one example: Some routers need to be rebooted after settings have been applied. Either by design or by a bug this some times helps. My Netgear here at home normally doesn't have any trouble, but every now and then when I set up a new port forwarding rule it wont work till I reboot the router.

So all you need to do is pull the power cord, wait a few sec. Then plug it back in. Make sure to give it time to come back up before you test again. Turn ON windows firewall! Believe it or not, I have helped a few people where the port forwarding wouldn't work with the firewall off in windows. No other firewall was installed. So when I was scratching my heading trying to fig out what was going on I decided to turn the firewall back on, add the ports to the firewall to let them through and it worked!

So this is also another thing you can try. I still cant explain it myself. As per 2 if you use only the windows firewall try adding the ports your forwarding to it, not just the program that is going to use them. The simple port forwarding program makes this easy with one click on the tools menu.

I have helped a few people where once the ports where added everything worked fine. If you haven't been able to tell, the windows firewall can be a bit strange on some systems! Yes I know this is a easy answer but let me explain. There is some malware out there that installs a network driver that hijacks your connection, and every webpage you go to gets redirected to an advertisement. This shows that malware, viruses and other things can easily hijack the network and really screw things up.

This is for you Verizon users out there. No port forwarding of any kind would work and every time we added a new rule the router complained the port was already in another rule Even though the user had no other rules set up.

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Simple, Free, Port Forwarding Software - By Port Forwarding Wizard. What is Port Forwarding? Port forwarding, can be called port mapping. A word of definition of port forwarding is a way that bridge the communication between one side and another side. The online Port Forwarding Tester is a tool to let you check if the port is opened on your router. Sometimes, even you have already added port forwarding entry into router, but the online tester still show the port is closed when you test.