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Network was stable, now isn't anymore
MatthewHSE
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Joined: 20 Jul 2004
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Location: Central Illinois, typically glued to a computer screen
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I administer a small network of four PC's, all running W2K SP4, kept relatively up-to-date through the automatic updates (never installed without review first).

I just built a new computer and swapped it with one of the old ones. I kept the network identification the same between the two machines, in other words, the rest of the networked computers shouldn't even know a change has taken place.

Since taking out the old computer and putting in the new, though, our network stability has gone way down. We use Outlook XP for our e-mail, with all the PST files residing on one machine (not the one that got replaced). After I replaced that one computer, we've been having problems with our network connection apparently dropping very briefly, and then we can't read our e-mail until we restart Outlook. The same thing happens with documents and databases stored on other computers; we'll be working along just fine, then suddenly can't save and lose our changes.

I've checked all the connections and they're tight. Nothing else has changed. Where should I begin to try to find this problem?
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erikZ
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Joined: 30 May 2004
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There's a bunch of things that can cause network instability. The first thing to do is go to the administrative panel, select event viewer, look in applications and system, look for red flags, click each to see what it is. Network related ones are the main ones you are looking for, also any hardware type ones.

You can find more information on each error by going to eventid.net, entering the event id number and the event source, see if you can find more information.

That's the first step.
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MatthewHSE
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Joined: 20 Jul 2004
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Location: Central Illinois, typically glued to a computer screen
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Hey, thanks. Didn't know about the Event Viewer before (goes to show I don't "administer" this network as much as I just "set it up.")

Preliminarily, it looks like I need to assign each computer it's own local IP address. I've done that before, if I could only remember how . . . I'll give it a try and post back here with the results.
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erikZ
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If you are using a router with DHCP you don't need to assign static IPs to the machines, but the truth is if you do the network will run a lot better in general, especially as a windows network.
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techAdmin
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Joined: 26 Sep 2003
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To assign an IP address, you will need the following information:

Your router IP address on your network
Your IP addresses, they always start with 192.168, then usually .0, then you can number them from 1-255, so a sample IP would look like this, assuming your router is 192.168.0.x

machine one: 192.168.0.1
machine two: 192.168.0.2

and so on, it doesn't matter which number you use in the last thing as long as it's unique on the network and <= 255.

You will also need to know your dns servers I think, you can find those now by opening the command line in windows:

start -> run -> cmd

that opens up a command line screen.

type in:
ipconfig /all

You'll see your ip information there.

I usually use the router ip address as the first dns server, that might be wrong, but it works fine, it's the gateway to the web, then make sure you have a real dns server listed, ipconfig should give you that information.

The open up control panel -> network and dialup connections.

In network and dialup connections right click on your LAN connection, select properties. Scroll down the list of network protocols until you get to TCP/IP. highlight that, then click the properties button. This will open up the ip configuration screen.

This is where you assign all the stuff.

First is to select Use the Following IP address.
Type in the address.
Your subnet mask will be 255.255.255.0

Don't worry about what a subnet mask is for the time being, just type that in.

You can try to see if it works if you select 'obtain dns servers automatically', but I like manually entering it, I never have any trouble doing that. I don't think you need to change any of the advanced settings.

TCP/IP stuff is pretty interesting, it's what makes all networks, including the web, work, so if you work with the web, understanding how networks run is pretty useful in the long run. And networking a home system is a good way to learn. For example, you can set up apache on one machine, then access it from another, this requires manually adding some information to the HOSTS file in windows:

WINNT/system32/drivers/etc/hosts

Hosts has no extension, but it's just a text file, it's how all computers used to find each other, but it's still very useful for local networks, even within a single computer, for example, I have on my development box all my websites, and the host file has a list of abbreviations for them, which point to 127.0.01, which is your local machine loopback ip address, that means that it sends anything sent to that back to itself, where apache grabs it, so all I have to do to run a site on my box, or any other box I've set up with a hosts file [the other boxes of course have the ip address for those abbreviations set to the ip address of my dev box.] is go to a browser, type in ba, and my ba site pops up, just like on the web, since I'm running a small web in my house.
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MatthewHSE
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Joined: 20 Jul 2004
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Location: Central Illinois, typically glued to a computer screen
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Thanks, I went through that just fine, but found that, with our setup, I wasn't able to assign IP addresses AND share our Internet connection at the same time. I think the reason for this is, we don't have a DSL router. We just have a network hub, which we use to connect the four computers, and one computer has an extra network card which we plug the DSL into. The other computers then get their Internet connection over the LAN.

Setting the IP address for a computer manually also requires setting the DNS manually. We don't have a router to have a DNS address, so I tried leaving the settings blank, and also tried adding the DNS settings for our ISP. In both cases, the computer that had the extra network card and the DSL line plugged in could access the Internet, but the other computers couldn't. So for now I've left the IP addresses to be assigned automatically, and we'll have to deal with network instability until I can figure out another solution.

Given our setup, do you know of a way I can assign IP addresses manually, but still use the LAN DSL connection without getting a router?

Thanks for all your help,

Matthew
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techAdmin
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Joined: 26 Sep 2003
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Oh, I see, you're trying to use windows automatic internet connection sharing, that's total garbage, you're wasting your time. A router costs about $30, if I'd been doing a job like this billing a standard, or even reduced rate fee, I would have already charged about $100 to get something that will never really work working, this is a case to total false economy, not to be harsh, I stopped helping friends try to save a few dollars a few years ago, when I realized that every $10 or so I saved them usually ended up costin me at least 2-3 hours of time, often much more. Your case is the same.

When you use windows internet connection sharing, it automatically assigns an IP address, if I remember right, to each machine, can't remember exactly how it works, but it's a total waste of time.

A router takes every request sent out from an IP address to the network, then sends back that request to the machine when it receives it, it routes the requests. You can get a network to work without a router using 2 networking cards, but it's a pain, you have to set up a DHCP server on one of the machines, plus a bunch of other stuff that never really works quite right unless you are pro networking guy.

It's not worth the $30 you are saving to try to get this running to be honest, just go out and pick up a $30 netgear router and your problems will all be solved.

Networks work best when they are networks, real LAN networks, that windows garbage is just that, garbage.

I'm sure there is some way to do it, but why? Currently your network is totally exposed to the web, it's totally insecure, for no benefit.

Our local Computer store has better prices than this netgear router, but this one is just $41.

If you have a craigslist.org in your area you can often find these things used or refurbished for about $20-25.

I wouldn't dream of trying to set up a network using internet connection sharing if that' what you're doing, I tried it about 4 years ago with dialup, before I knew better, it worked sort of sometimes in certain situations, but once you get a router you'll laugh at yourself for how much time you just wasted to get a bad system barely running.

:: Quote ::
So for now I've left the IP addresses to be assigned automatically, and we'll have to deal with network instability until I can figure out another solution.


Your IP addresses aren't being assigned automatically because you don't have a router, one of the things a router does is to automatically assign IP addresses to the network, then route all requests from and to those ip addresses to the correct machine. The router contains what's called a DHCP server, which is what assigns the IP addresses automatically, routers do a lot of things.

Also, if you are actually using a hub, not a switch, it's not going to work very well, hubs blast out everything to everything, switching hubs are smart and only send data to and from the requesting resource, your computers in this case. If the hub doesn't say it's a switch, then it's a hub, although those are getting much less common nowadays since there is no advantage to using a simple hub, and switching hubs do everything hubs do plus direct traffic.
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how to go about doing this...
andy
Status: Interested
Joined: 15 Oct 2004
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I apologize if my response is overly verbose, overly basic, or covers information that you already know. Just my $0.02. To people like me who work with computers a lot, this stuff seems a lot more intuitive than it does to someone who has never administered a network before, so it's hard to know what is going too far. But I've been there, and I feel your pain. That is the reason why I typed out this little guide to help you along the way.


Overview of what your game plan should be:

(Explanations Later... it's easier than it sounds from the description!)

1) Buy a router, connect it to the net.

2) Set it up so that the DHCP server is giving your workstation computers their IP addresses when they ask.(usually this is the case by default)

3) Set up the range of IP addresses that your DHCP server can use to assign IP addresses.

4) Configure your workstation computers to use DHCP to obtain their IP addresses.

5) Configure your server(s) to have a static (permanent, non-changing) IP address that is outside of the range of addresses that your router uses for DHCP.

6) Configure your router to forward all necessary ports from the outside world, to your internal server(s).

(on a quick side note for clarification, 192.168.* is what is called a private IP range. They mean nothing on the internet itself. Everyone that buys a netgear router by default will have one real IP address for the part of the router that is connected to the internet, and a 192.168.0.* network internally for all computers that are hooked up to it.)

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1) Buy a router, connect it to the net:

What a router does, and why you need it:

A device that routes your computer's network traffic, is cleverly called a router. These days, home and small office routers have much more functionality than simply routing traffic from here to there, they are complete network management devices. They provide important services such as Port Forwarding, and DHCP. Lets take a look at the last one first.

DHCP (Dynamic Host Configuration Protocol) automatically assigns an IP address to your computer upon booting, or (re)starting the network services on your computer. These days, it is definitely the most common way for workstation computers to get their IP address. When your computer boots up and it turns on it's connection to the network, it will look for a DHCP server on your network by sending out a request to all computers on your network (called a broadcast request) and seeing who responds to it. The DHCP server will respond with an IP address, other information such as default gateway, a few other things that we can safely ignore at the moment, and the amount of time that the given information will be good for before it has to renew. The server will keep track of what computers are assigned what IP addresses on your network, so nobody gets the same one. The DHCP server is either a computer on your network, or as is more commonly the case on small networks, it is a hardware network routing appliance such as a linksys or netgear home/small office router. Most computers (all windows computers I believe) by default are set up to get their IP addresses from DHCP... so for the computer to not be using DHCP, you would have had to specify a unique IP address for the machine either during installation, or after installation, but before you could connect to the network. Without an IP address, a computer can not use the network at all.

Why it matters...
Picture your network as being a big room (lets call that room 192.168.1.*) with a numbered door for each computer.

When a computer is using DHCP: When your computer is just booting up, it will wake up in that room, scream out and ask what door it should go into, someone comes out from behind a door and tells them. The computer will go into the door that it is told to go into. So if they were told to go to room 7, then they would be in 192.168.1.7

When a computer is not using DHCP (known as a static IP address): Each computer is always behind the same door. So Bob's computer wakes up with a note in it's hand saying to go to door number 9, making his address 192.168.1.9. Each time you add a computer to the network, you need to remember who is in what door, and make sure that you permanently assign it an unused door.

So when the router has something to send to that computer, it will send it to the appropriately numbered door. If you've got computers that are connected to the network that are permanently assigned doors, there is no way for the DHCP server to know that, and could very easily ignorantly tell the computer of Jill from Accounts Payable to cram into door number 7 with the computer of Mike from Corporate Finance... and boy oh boy will that router be mad when it tries to slip memos to Jill under that door, and every time it gets a note slid back under the door from Jill saying "thanks, signed door number 7" and one from Mike saying "This isn't my memo, get your sh*t straight, signed door number 7".

So for your size network, your average home/small office router should be fine. Almost all routers these days that are made by major manufacturers are compatible with all sorts of ISPs. Your router's documentation should tell you how to set it up to connect to the net.

**********************************************

2) Set it up so that the DHCP server is giving your workstation computers their IP addresses when they ask.(usually this is the case by default):

You are almost guaranteed not to have to do anything to get your router to do this.

**********************************************

3) Set up the range of IP addresses that your DHCP server can use to assign IP addresses:

How to do this is specific to your router. Most likely it's going to be something that you can easily configure through a web browser interface.


**********************************************

4) Configure your workstation computers to use DHCP to obtain their IP addresses:


How to check which machines are using DHCP:

First of all, you want to go into the configuration of your router and find out what range your computers are assigned addresses from. For example, if your network is 192.168.1.[1-254] then your DHCP server should be assigning people addresses between, lets say 192.168.1.[1-100]. If that is the case, then any machine that you want to statically assign a unique IP address to, you should assign it one over 192.168.1.100 so you know that DHCP isn't going to give one of your machines the same address that one of your static machines has. If your router us set to use all of 192.168.1.* for DHCP, you should either find a way to limit it's addressing range, or (in the absolute worst case "you should return this router" scenario) just set your server(S) IP address to something that is as high as possible.

Write down the range of addresses that your DHCP server uses.

On each computer on your network (ugh, yes... all of them) Go into the properties dialog for your LAN connection. (The one that has a list of things like "Client for Microsoft Networks", "File and Printer Sharing for Microsoft Networks" and "Internet Protocol (TCP/IP)") Select "Internet Protocol (TCP/IP)" and hit the properties button just below the box. If the "Obtain an IP address automatically" radio button is selected, then you get your IP address using DHCP. If it is not checked, then you would always have the IP address that is specified there. Write down how each machine is set up. If you find any machines that have addresses that are permanently set to a number that is within the range of addresses that your DHCP server uses, then you should immediately change those to something that is not within that range, and reconfigure your computers to point to the right sever.

Next, go to one of your DHCP workstations and go to start>run and type "cmd". When the DOS prompt comes up, type "ipconfig /all". Write down your "subnet mask", your "Default Gateway", and your "DNS servers".

**********************************************

5) Configure your server(s) to have a static (permanent, non-changing) IP address that is outside of the range of addresses that your router uses for DHCP:

Now, on your server, go into the properties dialog for your LAN connection. Select "Internet Protocol (TCP/IP)" and hit the properties button just below the box. You want to make sure that you set an IP address that is not going to be double-assigned by DHCP. For the default gateway, subnet mask, and DNS servers, enter the values from your workstation. Make sure that all of your servers have their IP addresses permanently set. For the sake of stability, you do not want to have your servers be using DHCP.



Alright! Now your network is properly set up internally! Now, you need to make your server accessible from the outside world. This is done through Port Forwarding... and this is the easy part.

**********************************************

6) Configure your router to forward all necessary ports from the outside world, to your internal server(s):

Basically, each computer talks to each other computer through ports. If you think of your computer as a building, think of a port as a door into and out of that building. Just like door 1 on a building might be for the mail room, and door 2 might be for laundry, Port 80 for example, serves web pages and Port 25 accepts incoming email. What happens though if you have a high security access controlled industrial park for all of your buildings, and you don't want the Lucky Star Laundry company or the USPS even knowing which building does laundry or mail? Well, everyone that is in the compound will be able to get to the mail room and laundry without a problem, but nothing from outside is getting in. You could set up a couple of entrances on the outside of the compound that say "Mail delivery/pickup Here" and "Laundry delivery/pickup here" and have your own internal system for getting the new deliveries to the proper building, and the stuff to be picked up to the proper entrance.
This is basically what you are doing with your internal network. When mail is going to be sent to your network, it's not going to have a way to get from the router, to your exchange server. For this, all you need to do it tell the router to forward any connection to port 25 that is receives to the internal 192.168.1.[whatever] address of your mail server. This process is called Port Forwarding and should be done for each service that you have running. For example, lets say you had a web server on your internal network:

Web server is running on 192.168.0.100. Web servers use port 80.

Lets say your router has an external address (the one given to you by your ISP) of 123.123.123.123

if someone puts 123.123.123.123 into their web browser... their web browser will send a request to port 80 for that IP address. Your router will receive the request, and see that all requests for port 80 are supposed to go to 192.168.1.100, so it will merrily forward the connection request along to the internal IP address.

Just have your router forward all the necessary ports to your internal server(S) and you should be fine. A server that handles incoming mail needs to have port 25 forwarded to it. A machine that handles POP3 needs to have port 110 forwarded to it. This will be very very easily accomplished by taking a quick trip to the router's manual, and looking for port forwarding. It is literally as easy as entering in the internal IP address and the port number!

**********************************************

Bang! Should take a MAX of an hour to two (i, who has done this a million times could do this with a 5-10 computer network in no more than 25 minutes). I'm sure that I left some things out, so if you have any questions, post 'em!
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techAdmin
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Joined: 26 Sep 2003
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Andy, very happy to see you here, welcome, thanks for taking the time [MatthewHSE, this guy is very good at what he does, he knows what he's talking about]

Hope to see you here now and again when you have the time, again, thanks for stopping in Andy.

Just to clarify something that andy said, you only need to do port forwarding if you are running a specific service on a specific machine, for example if you are running pcanywhere or VPN hosts on a machine, it needs a static IP network address, and will need the necessary ports forwarded in the router to that IP address. Normal email and browsing do not require port forwarding, only mail and web servers, and so on.

TechAdmin
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Good References
andy
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Joined: 15 Oct 2004
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Oh, I forgot to mention that as far as I am concerned, the best reference material that you are going to get is put out by O'Reilly and Associates... but for a cheaper alternative that targets people who haven't been doing the stuff professionally for more than a small amount of time, the "for dummies" books are great. Although they can be excessively verbose at times, and sometimes pussyfoot around the more complicated issues, sometimes that's really what we need. (and come to think of it, is exactly what I did in my previous post.)

Oddly enough though, I've seen a lot of O'Reilly Reference Library stuff pop up online in nice pretty professional looking formats. Not sure what prompted that, but here is a link to one. I think that in your situation, you'd be most interested in reading "TCP/IP"
www.unix.org.ua/orelly/


BTW: Thank you for the kind words, and I'm glad to be here techAdmin. I hope to have lots of time to post in future threads.
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