Q on port forwarding and triggering.

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Q on port forwarding and triggering.

Postby triggerhappy41 » Fri Sep 10, 2004 11:05 pm

So its my understanding that when you forward a port/ports, a new connection can be initiated though those ports from an outside computer. This allows for servers and other nice little things.

But, my question is, does this only work for one specified computer behind the firewall? If I want port 6112 open for battlenet, and I forward it to the computer at 192.168.bla.bla (My computer's internal ip), will my bro, which is at a different internal ip, benefit from this forwarding, or would it not affect him at all? I would like for a forward to work for all the computers on the network...

And as for triggering, ive just discovered it in my router setup page. So I was wondering if the basic idea was that a connection established by the compuer behind the firewall would also open up a chunk of ports around the inital port? Sorry if I worded it bad, but is that the idea?
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Postby Hardware Junkie » Sat Sep 11, 2004 3:05 pm

If you forward port 21 from your router to 192.168.2.1, only that PC will ever get contacted on that address; unless there was initial comtact made from another IP address.
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Postby dr_st » Sat Sep 11, 2004 7:10 pm

I'm jumping in this question, because it has also been bothering me for a while.

If you have N machines behind a router (in my case, 3) and you want ALL of them to accept incoming connections on port P, which isn't one of the standard ports, how can it be done? I tried port forwarding, but it limited me to one PC per port.
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Postby triggerhappy41 » Sat Sep 11, 2004 8:37 pm

thats basically my question too. I want ALL of the computers on the network to be able to recieve incoming connections from certain ports.
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Postby Hardware Junkie » Sun Sep 12, 2004 10:46 am

Not possible. In order for multiple computers to recieve incoming connections on the same port, they would need individual IP address that exist on the outside network (in this case the internet).

Example.
DSL setup. You run a connection manager on all machines with the DSL modem hooked up to a SWITCH (not a router). Each machine would have its own IP address in which internet users could connect to.
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Postby dr_st » Sun Sep 12, 2004 11:58 am

Hardware Junkie wrote:Not possible. In order for multiple computers to recieve incoming connections on the same port, they would need individual IP address that exist on the outside network (in this case the internet).

Example.
DSL setup. You run a connection manager on all machines with the DSL modem hooked up to a SWITCH (not a router). Each machine would have its own IP address in which internet users could connect to.


How come just plain browsing works then? Correct me if I'm wrong, but HTTP is just another protocol, using just another port. How come this port gets to all machines without anyone even having to configure anything?
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Postby Hardware Junkie » Sun Sep 12, 2004 1:20 pm

You make the initial request, thus the router keeps track of it. It knows what you requested and thus, when it gets a response, sends that data back to the appropriate person.

But the reverse would never happen. If a computer makes a request to your router, the router would have multiple computers to choose from.

However, you can broadcast the same type of server on different ports.

Computer 1 could have FTP broadcasting on 21
Computer 2 could have FTP broadcasting on 33
Computer 3 could have FTP broadcasting on 77

Your router could be setup to route from its IP address to the individual computers, depending on what port the router was contacted on.

RouterIP Port 21 ---> Computer 1
RouterIP Port 33 ---> Computer 2

etc...etc...
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Postby dr_st » Sun Sep 12, 2004 7:50 pm

Hardware Junkie wrote:However, you can broadcast the same type of server on different ports.

Computer 1 could have FTP broadcasting on 21
Computer 2 could have FTP broadcasting on 33
Computer 3 could have FTP broadcasting on 77

Your router could be setup to route from its IP address to the individual computers, depending on what port the router was contacted on.

RouterIP Port 21 ---> Computer 1
RouterIP Port 33 ---> Computer 2

etc...etc...


That's what I did. I was just wondering if there was a way around it. Well, thanks.
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Postby Comp_parter » Mon Sep 13, 2004 5:30 pm

triggerhappy41 said:

But, my question is, does this only work for one specified computer behind the firewall? If I want port 6112 open for battlenet, and I forward it to the computer at 192.168.bla.bla (My computer's internal ip), will my bro, which is at a different internal ip, benefit from this forwarding, or would it not affect him at all? I would like for a forward to work for all the computers on the network...


This is a problem of calling access points that have nat capabilities routers.. You should be able to open any given port for a range of ip addresses, a cisco router would have this capability, wanna spend $1800.00, if so you can have one of those handy lil' devices, oops don't forget you'll have to program it from command line as well.. Good Stuff!!

I'm in the same boat as you, my netgear router :roll: can't do it either, but hey it only cost $49.99 :D
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Postby Hardware Junkie » Mon Sep 13, 2004 6:38 pm

Comp_parter wrote:triggerhappy41 said:

But, my question is, does this only work for one specified computer behind the firewall? If I want port 6112 open for battlenet, and I forward it to the computer at 192.168.bla.bla (My computer's internal ip), will my bro, which is at a different internal ip, benefit from this forwarding, or would it not affect him at all? I would like for a forward to work for all the computers on the network...


This is a problem of calling access points that have nat capabilities routers.. You should be able to open any given port for a range of ip addresses, a cisco router would have this capability, wanna spend $1800.00, if so you can have one of those handy lil' devices, oops don't forget you'll have to program it from command line as well.. Good Stuff!!

I'm in the same boat as you, my netgear router :roll: can't do it either, but hey it only cost $49.99 :D


Except that you need to have those IP addresses in order to do NAT. A service provider gives out dynamic IPs, there is no telling what IPs are available, or if they would always be available to your network.
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