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Cable Guy - How to Get on with your Resident Network Engineer
Web Monkey About the Author

With security clearance and well over a decade of experience with SQL Server, Web Monkey is the resident DBA at Norb Technologies and a real database guru.

A regular contributor to SQL Server Club, his background includes software development, hardware, a smattering of essential networking knowledge and an unhealthy interest in web security. He has an obsession with automating repetitive tasks, but has a tendency to forget where he left his last open bag of fruit and nut...

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Networks. The bane of many peoples' lives. Whether it's getting the internet to work at home or setting up cross-domain trusts across sites, network knowledge is a really useful thing to have. Unless we’re qualified network engineers, most of us don’t have a lot of knowledge in this area, we’re usually a specialist in another area, such as software development or SQL Server.

Yet in many companies the database and network people don't exactly, how can I put this… gel. This is a bit strange, considering how dependent we are on each other. Let's face it, a standalone SQL Server database isn't really useful until it becomes multi-user and the only way to do that is with a network. And when the network goes down, the database isn't much use.

So imagine that your network is down, your SQL Servers are inaccessible and users are calling you up to ask what’s wrong. As a DBA or developer this is when you’ll need to converse with your resident Cable Guy to get the problem fixed and make sure your SQL Servers are up again as soon as possible.

The chances are your users will have scant (if any) network or database knowledge. Ok so you’re the database specialist, but having a few network skills is beneficial in getting your databases back online as quickly as possible to have users up and running again without delay.

You’re going to need to talk to the Cable Guy and if you can provide as much useful information as possible, it saves a lot of time troubleshooting the problem and you may even fix it yourself.

Here's a brief guide to getting the most out of those unsung heroes of IT support, your network guys. The following five points take you through some simple troubleshooting steps that any DBA or developer can do, however basic your network skills.

  1. Ping It

    If you can't ping a server that used to work, there's a good chance either you or it are disconnected from the network. From a DOS command box on your PC (Start > Run > cmd), type the following, replacing SQLProd1 with the name of your SQL Server:

    ping SQLProd1 or ping -t SQLProd1

    Step 1: Ping the SQL Server

    If you don't know, -t makes ping work continuously until you interrupt it with a CTRL+C. This is quite a useful option as it will show the response from the server as soon as it comes back online, without you having to continually type the ping command.

    If everyone else around you has lost their connection too, then it’s a network problem, not just you. If the server doesn’t come back online after a few pings, call the network guy and tell him it’s inaccessible and you can’t ping it.

  2. Is it a DNS Problem?

    If a server stops working that used to work, try pinging its IP address instead from a DOS command, eg:

    ping 192.168.0.44 or ping -t 192.168.0.44

    Step 2: Ping the IP Address of the SQL Server

    Why? Because sometimes, an entry is removed from your DNS or is changed which stops the correct IP address being picked up. If you don't know what a DNS does, it is simply a lookup table on the network which your machine goes to, in order to find the IP address of a server when you specify the server's name.

    If you find you can successfully ping the IP address, but not the server name, then it's most likely a DNS issue, or the server name doesn't match the IP address in your hosts file (see point 3). You’ll want to tell your network guy that you’ve pinged the IP address, but there seemed to be a problem with its entry in the DNS file.

  3. Know your Hosts File

    Your hosts file is like a local DNS - it's simply a lookup table held in a text file, which is resident on your local machine. As a quick fix it can be used to add a server name/IP address lookup, so that you don't have to remember loads of IP addresses. Using Windows XP, you can find it in:

    C:\WINDOWS\system32\drivers\etc

    Double click on the hosts file and choose to open it up in Notepad. Then add an entry:

    127.0.0.1 localhost
    192.168.0.44 SQLProd1

    Step 3: Update your hosts file

    If you still have problems, tell your network guy what you have done and that you still can’t connect.

  4. Can you Ping Anything External?

    If it's not an internal server but an internet site that you can't reach, ping can once again come to the rescue again. Open up another Dos command window and ping a common site which you know is almost guaranteed to be up and running, such as Microsoft, the BBC or Amazon.

    You won't always get a response from them, as some firewalls block outgoing pings, but if you can ping one site but not another, there's a good chance it's down, rather than being a problem with your network or internet connection. If you don't know how, a simple:

    ping www.bbc.co.uk

    ... should do the trick.

    Step 4: Ping an External Web Site

  5. Make Sure you've not become Unplugged!

    If your colleagues have a connection but you don't, then the prime suspect is probably your own machine. Check that the cable's plugged in to the back of your machine (yeah, obvious, but it happens more often than you’d think!), before you go calling the network guy. You can save him some bother by making sure it’s nothing as embarrassingly simple as your network cable coming unstuck.

    Check that the two little LEDs, either side of where the cable plugs in, are on - one should be steady, the other flickering as data comes down the cable. Never looked at it? Then take a look now. If the problem's intermittent, then there's a chance it's a dodgy connection, which might mean a faulty network socket.

    But more often than not it’s the cable. Cables get abused, crammed behind radiators, flattened under heavy desks and rolled over by office chairs. Take care of your cable and if it looks worse for wear, replace it. And you know who to ask nicely for a new one, don’t you? Your new friend, the Cable Guy.

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