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2 modems

Posted on 1998-08-14
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Last Modified: 2013-12-27
I have on my NT server 2 modems that connects to  different ISP's.I want to direct my users to pass from the 1st or the 2nd modem when they are open simultanesly.What i have is that i open the 1st modem they pass throught it when i open the 2nd they stop pass throught the 1st and they pass throught the 2nd.
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Question by:nous
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12 Comments
 
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Expert Comment

by:joe_massimino
ID: 1147595
First you will need a proxy server installed for your users to all use the same shared modem connection. I don't think you can put your users on two ISP's at the same time. Actually, if they both connect to the Internet, why would you need to?  There are many reasons to have two modems going to the same ISP, say for tunneling protocol, but the modems would not be under the control of your users in that they can control which path to take.
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Accepted Solution

by:
Otta earned 800 total points
ID: 1147596
It's a question of "routing" the IP-traffic.
Starting to use the first modem sets up a "default" route,
and starting to use the second modem deletes that route,
and creates a new "default" route.

So, you need to "manually" use the 'route' command
to define which "target" range of IP-addresses
are to continue to be accessed via the first modem,

Example:
  route -fh add net 129.34.10.0 129.34.10.60 1



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Expert Comment

by:joe_massimino
ID: 1147597
There is no practical way to handle this situation.
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Expert Comment

by:Otta
ID: 1147598
> There is no practical way to handle this situation.

I disagree, strongly!  See my previous comments.
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Expert Comment

by:joe_massimino
ID: 1147599
How do you route addresses when they can all be reached by either route?  How does he determine which route to assign to each modem. If this were two private networks he was connecting to I could see it, but when they both connect to the Internet, I don't see this being very easy to implement.
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Expert Comment

by:Otta
ID: 1147600
> How do you route addresses when they can all be reached by either route?
> How does he determine which route to assign to each modem.

How? The 'ROUTE' command defines the routing.

The actual "routes" which are defined can be based
on the "properties" of each ISP, namely the IAP
(Internet Access Provider) to which they connect.

For example, one ISP in my town connects to the '@HOME'
network, which is operated by the cable-TV companies
in the USA and Canada, while another ISP connects,
over a very few "hops", to CA*NET and MCI and SPRINT.

So, it makes sense to route IP-addresses 24.xxx.xxx.xxx
(@HOME network) via the first ISP,
and route traffic to '128.100.xxx.xxx' (University of Toronto)
via the second ISP.

There is no "hard-and-fast" rule;
you have to adopt the NIKE approach: Just Do It.
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Expert Comment

by:joe_massimino
ID: 1147601
I think your approach is good if the user has a profound knowledge of how Ip traffic is routed outside of his immediate network. The information you are using to justify your methods is not easily accessable to everyone in that not all users of the Internet have the same level of knowledge and understanding as you.  The best analogy I can think of would be for me to say how simple it is to remove an IC from the chassis of a TV set, and replace it with a new one. easy for me, yes, easy for many others, maybe, easy for everybody, no.
Your methods are useful only if you have a profound understanding of how IP is routed out of your ISP's.
I am not meaning to say you are wrong in any way.  I am reading the question, and I don't see that nous has what you suggest in mind, I think he is more thinking of his network and ISP's, he actually doesn't care which ISP is getting the traffic as long as it is the one he currently wants to get it. In other words, he will send the same traffic over both modems, just at different times.  Maybe I'm wrong and reading into his question too much. I have no doubt that you know what your talking about. :)
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Expert Comment

by:Otta
ID: 1147602
Rereading the question, it's possible that:
 - NOUS wants "redundancy", i.e., all traffic routes
   through whichever modem is currently "active"; or,
 - NOUS wants "traffic-splitting", routing of IP-packets
   to the "better" modem;
 - NOUS is experiencing the change in "default-route"
   when the 2nd modem becomes active,
   and this is deemed to be a "problem".

> I think your approach is good if the user has a profound knowledge
> of how Ip traffic is routed outside of his immediate network.

I don't think that a "profound" knowledge is needed.
If the person is competent-enough to get two modems
connected, at the same time, to different ISPs,
that's probably "sufficient" knowledge about TCP/IP.

> The information you are using to justify your methods
> is not easily accessable to everyone
> in that not all users of the Internet have the same level
> of knowledge and understanding as you.

However, having a forum like "Experts-Exchange" increases
the accessibility of such knowledge, correct?


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Author Comment

by:nous
ID: 1147603
otta,thanks for your answer and i believe thi is right.But forgive me how can i manually give this commands to each user in nt 4.0 server ,proxy...
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LVL 12

Expert Comment

by:Otta
ID: 1147604
> how can I mannually give this commands to each user

Do not tell each user. Instead, let the "server" do the "routing",
as part of the process where each modem is told to "connect"
to each ISP.
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Expert Comment

by:joopv
ID: 1147605
If you want more bandwith and redundance you could try to make a multilink connection to one of your providers.

A multilink connection is 1 logical connection with 1 IP address, but the traffic is split between 2 physical connections.

I'm not sure how to do this in NT, but in w95 it's a property of the  dial-up adapter you created (set additional device)

There are some drawbacks however :
- Not every provider supports multilinking (MLPPP).
- I don't believe it works very well with analog modems, it is meant to be used with ISDN lines. You should at least have identical modems.

But it's worth a try.

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LVL 12

Expert Comment

by:public
ID: 1147606
Diamond has a new modem which does exactly what you seek in win98. It should be possible with your modems and NT also.
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