Q on port forwarding and triggering.

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Postby Comp_parter » Mon Sep 13, 2004 7:08 pm

Hardware Junkie wrote:
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.


The external could constantly change without affecting what ports are open on your internal network, if a port is open, it's open.
I should be able to specify an address or addresses for what port is open.
For example ftp open for 192.168.1.25 thru 192.168.1.50.. There is no need for a new port number for each pc performing ftp
I know the example is over simplified :roll: but that fucntionality should be there.
It can be done, but the cheaper routers do not have this function
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Postby Hardware Junkie » Mon Sep 13, 2004 7:25 pm

Comp_parter wrote:Hardware Junkie wrote:
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.


The external could constantly change without affecting what ports are open on your internal network, if a port is open, it's open.
I should be able to specify an address or addresses for what port is open.
For example ftp open for 192.168.1.25 thru 192.168.1.50.. There is no need for a new port number for each pc performing ftp
I know the example is over simplified :roll: but that fucntionality should be there.
It can be done, but the cheaper routers do not have this function


Commercial routers have that function ypu are talking about. They are within the $50-150US range. My WRT54G has that.

I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3

THe more expensive Cisco routers have this function and are able to route in this manner, nut your Internet Service Provider would have to have your list of IP addresses assigned to you and only you for your use.
There are no internet service providers available to home users that provide this service (atleast for similar prices to cable or DSL).
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Postby Comp_parter » Mon Sep 13, 2004 8:29 pm

Ok I see what you're saying.

Hardware Junkie said:
I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3


So what I was saying won't work because the private IP addresses are invisible to the outside world.
FTP on the internal network would work fine because each pc has it's own IP Address,
but to the outside world that hidden network is attached to a constantly changing external IP Address.
So there is no way to distinguish
computer 1
computer 2
computer 3
without assigning different port numbers and giving it an internal route.
I think I got it...
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Postby Hardware Junkie » Tue Sep 14, 2004 5:25 am

Comp_parter wrote:Ok I see what you're saying.

Hardware Junkie said:
I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3


So what I was saying won't work because the private IP addresses are invisible to the outside world.
FTP on the internal network would work fine because each pc has it's own IP Address,
but to the outside world that hidden network is attached to a constantly changing external IP Address.
So there is no way to distinguish
computer 1
computer 2
computer 3
without assigning different port numbers and giving it an internal route.
I think I got it...


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Postby dr_st » Tue Sep 14, 2004 9:01 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.


Something else I thought up in relation to this. You brought up the example of a DSL model connected to a switch, thus allowing each machine to have its own global IP address. Seems to me that the same effect can be reached if you just turn off NAT on your router, because that will make it basically a switch. Of course, all under the condition that your broadband service provider allows you to have multiple IP addresses.

Hardware Junkie wrote:Commercial routers have that function ypu are talking about. They are within the $50-150US range. My WRT54G has that.

I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3

THe more expensive Cisco routers have this function and are able to route in this manner, nut your Internet Service Provider would have to have your list of IP addresses assigned to you and only you for your use.
There are no internet service providers available to home users that provide this service (atleast for similar prices to cable or DSL).


This, however, got me somewhat confused. What is "this" function that you mention commercial routers have and what is the function that expensive Cisco routers have? How does it differ from the original request?
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Postby S33K3R » Tue Sep 14, 2004 10:28 am

@Hardware Junkie
I thought cable ip addresses were static :? at least I know mine has been the same for quite some time. thats why the lease on the ip address gets renewed at the end of the year or when ever the contract is up.
having said that. would the first post then be posible if the ip from his isp was static? couldn't he just forward the port coming from the router to each ip addy? or perhaps I am still not getting it all?
Last edited by S33K3R on Tue Sep 14, 2004 10:39 am, edited 1 time in total.
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Postby S33K3R » Tue Sep 14, 2004 10:31 am

dr_st wrote:
Hardware Junkie wrote:Commercial routers have that function ypu are talking about. They are within the $50-150US range. My WRT54G has that.

I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3

THe more expensive Cisco routers have this function and are able to route in this manner, nut your Internet Service Provider would have to have your list of IP addresses assigned to you and only you for your use.
There are no internet service providers available to home users that provide this service (atleast for similar prices to cable or DSL).


This, however, got me somewhat confused. What is "this" function that you mention commercial routers have and what is the function that expensive Cisco routers have? How does it differ from the original request?

I believe your answer is in the bold text. that is the function. will have to read some more and check it out myself as I never tried forwarding the same port for 2 different IP addys, atleast not at the same time.
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Postby Hardware Junkie » Wed Sep 15, 2004 5:03 pm

dr_st wrote:
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.



Something else I thought up in relation to this. You brought up the example of a DSL model connected to a switch, thus allowing each machine to have its own global IP address. Seems to me that the same effect can be reached if you just turn off NAT on your router, because that will make it basically a switch. Of course, all under the condition that your broadband service provider allows you to have multiple IP addresses.


Yes assuming the broadband service allows multiple connections and you turned off NAT and DHCP, it would turn your router into a switch (basically).

dr_st wrote:
Hardware Junkie wrote:Commercial routers have that function ypu are talking about. They are within the $50-150US range. My WRT54G has that.

I am talking about NAT through multiple external addresses, not internal IP addresses.
To do the function that the original poster is thinking about, it would have to do the following.

Route Computer 1 ---> IP ADDRESS 1
Route Computer 2 ---> IP ADDRESS 2
Route Computer 3 ---> IP ADDRESS 3

THe more expensive Cisco routers have this function and are able to route in this manner, nut your Internet Service Provider would have to have your list of IP addresses assigned to you and only you for your use.
There are no internet service providers available to home users that provide this service (atleast for similar prices to cable or DSL).


This, however, got me somewhat confused. What is "this" function that you mention commercial routers have and what is the function that expensive Cisco routers have? How does it differ from the original request?


Commerical Routers from Linksys or Dlink do not have the software built in to route between multiple external IP addresses. Cisco routers and the like do have it built in. Falls under the NAT category.

S33K3R wrote:@Hardware Junkie
I thought cable ip addresses were static :? at least I know mine has been the same for quite some time. thats why the lease on the ip address gets renewed at the end of the year or when ever the contract is up.
having said that. would the first post then be posible if the ip from his isp was static? couldn't he just forward the port coming from the router to each ip addy? or perhaps I am still not getting it all?


Technically they are dyanmically assigned. Your computer does not make the determination, your ISP does. They could change it if they wished. When you sign onto the network, the system examines the mac address of your modem and assigns you the IP addresses assigned to you in the database.
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Postby dr_st » Thu Sep 16, 2004 1:34 am

OK, I think I understand now. I'll try to summarize it, please correct me if I'm wrong.

1) There is no way to do port forwarding for multiple machines with internal IP addresses behind a router.

2) To allow port forwarding between multiple machines, you need each to have an external IP address, which means the broadband service must provide it to you.

3) If you DO have multiple IP addresses and you want the same port open on all, you have the following options:

a) A switch
b) A router with NAT/DHCP shut off - functioning as a switch
c) A router with the ability to route between external IP addresses (like Cisco)
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Postby Hardware Junkie » Thu Sep 16, 2004 8:57 am

dr_st wrote:OK, I think I understand now. I'll try to summarize it, please correct me if I'm wrong.

1) There is no way to do port forwarding for multiple machines with internal IP addresses behind a router.

2) To allow port forwarding between multiple machines, you need each to have an external IP address, which means the broadband service must provide it to you.

3) If you DO have multiple IP addresses and you want the same port open on all, you have the following options:

a) A switch
b) A router with NAT/DHCP shut off - functioning as a switch
c) A router with the ability to route between external IP addresses (like Cisco)


Mostly correct in all cases.
With #3 - "If you DO have multiple external IP addresses and you want the same port open on all, you have the following options"

At one point when I was using a Switch setup instead of a router with DSL, I was able to make an internet connection on each machine. I would go through the motions of signing on to the internet on each machine. This would give each machine an individual external IP address that people could connect to. In that instance, I could have run FTP servers on all machines and people would have been able to connect.
But the internet connection was deminished accross the multiple connections. I had super slow internet access at some points because there was no way for the switch to share the internet connection between computers. One system could hog all the bandwidth.
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