Network and Broadband Testing

Common faults and quick resolutions

No internet connection? Check your IP address as instructions below, if the IP address starts 169 try switching off your router and computer and then switch your router after 30 seconds and computer after 1 minute. If you have a cable modem or other similar setup where an access point or switch is connected, the modem must be switch on first followed by the connected device then the computer.

Slow internet connection? Check ping times to the web site you are experiencing issues with, run a trace to it too.

Slow downloads speeds? As above check the site you are downloading from. If it has a good response time then the site may be busy, restrict download speeds or not have the capability.

Command line tools for Windows

This page has been updated to make things a little clearer, please let me know if there are any problems. Essential knowledge! Some tests are run from a Command Prompt. It is accessed by clicking the START button click RUN and type CMD for windows 2000 onwards and COMMAND for 98 and previous. Click OK or press Enter on your keyboard to access the shell. It is a black and white screen, the flashing cursor after the prompt is where commands are entered – the mouse can be used to highlight and copy – simply click and drag the mouse over the text to be copied and press enter. Right click will paste text after the flashing cursor. If I mention that a test must be run from a DOS Window then follow the above steps to access it.

Key

Each section starts off with the command filename and is formatted in BOLD ITALICS. Text copied from the DOS window is in Courier New Font Text, the text in italic is the command you type in the DOS Window.

Commands covered here are –

• IPCONFIG

• PING

• TRACERT

• NETSTAT

IPCONFIG

What it does – Ipconfig displays your computers IP (internet protocol information)

Why use it – The information retrieved from the command enables you to start diagnosing faults with your connection

How to use it – This command is run from the DOS Window. Type ipconfig for basic information as shown below. You may use ipconfig /release or ipconfig /renew these switches allow the connection settings to be ‘released’ or ‘renewed’.

C:\Documents and Settings\home>ipconfig

Windows IP Configuration

Ethernet adapter Main Pipe:

Connection-specific DNS Suffix. . : lan
IP Address. . . . . . . . . . . . : 192.168.1.64
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.254

The Results – The information you are most likely to need is the IP address and the default gateway. The IP address is like a ‘phone number’ for your computer, there are private IP address ranges for networks these cannot be used on the internet, the addresses used on the internet are known as public IP addresses. You may also come across an IP starting 169 this is an automatic private internet protocol address or APIPA, if an IP address cannot be obtained from a DHCP (Dynamic Host Control Protocol) then the operating system will assign this type of address. In windows when you see warning “This Connection has Limited or No Connectivity” means an APIPA has been assigned. Tip, try switching off your network devices for 30 seconds or so, switch them on and restart your computer, this usually clears minor ‘hiccups’.

PING

What it does – Tests connectivity and or response times from a web site or IP address

Why use it – Allows you to determine if the domain or IP is active and if it is responsive

When to use it – If you cannot connect to a web site, it is loading very slow or for network connectivity issues

How to use it – The PING command is run from a DOS Window! There are other options you can use but the basic ping command is suitable for general testing. The basic command is to type ping followed by a host name or IP address. Example ping bbc.co.uk or ping 212.58.224.85 This will result in the following

C:\Documents and Settings\home>ping bbc.co.uk

Pinging bbc.co.uk [212.58.224.131] with 32 bytes of data:

Reply from 212.58.224.131: bytes=32 time=15ms TTL=123
Reply from 212.58.224.131: bytes=32 time=14ms TTL=123
Reply from 212.58.224.131: bytes=32 time=14ms TTL=123
Reply from 212.58.224.131: bytes=32 time=15ms TTL=123Ping statistics for 212.58.224.131:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 14ms, Maximum = 15ms, Average = 14ms

Interpret the results – The hostname bbc.co.uk has been resolved to its IP address by a DNS Server (a Domain Name Server – think of a phone book, name and number). Then a packet of 32 bytes was sent to the host bbc.co.uk resolved to 212.58.224.85 four times and a response was received four times. This indicates the host has responded and sent a reply back without any loss, this says the host is ‘up’ and working.  Next the timings, always in ms – milliseconds, the further that you are from the host and/or depending on network traffic you will see a variation in the timings. (Note: It is not easy to advise on timings, as different hardware, software and configurations will have an impact, I will guess some timings but it is best to use more than one test to identify faults) Local networks may have timings of <1ms to 50ms, UK to UK 10ms to 150ms - UK to Europe, 50ms to 300ms – UK to USA 200ms +/- timings are estimate only. You may also find an asterisk in the results; this can mean a few things. If you are seeing high timings and a few asterisks then the server may be busy there may be a lot of traffic on the network. It could be the server is offline or an outage or simply the server rejects pings and does not reply.

How YOU can use this test to diagnose – Using the basic ping command, you can test devices in your home network or office to see if they are on or offline, if there is any delay. Some examples for you are listed below and can be copied as required. Testing your broadband connection Note: If results are no loss (0% loss) continue to next step or stop and following link to restore connection

• Establish your IP address and default gateway using ipconfig (should not start 169 if it is do not continue and see repairing broadband connection)

• Ping local loop back to test TCP/IP – ping 127.0.0.1

• Ping gateway – ping [enter IP address from IPCONFIG for default gateway

• Ping IP address – ping 212.58.224.85

• Ping hostname (also tests DNS resolution)

If there were no faults or loss your connection looks ok, depending where its failed identifies where the problem may be. If your IP address starts with 169 this is a private address assigned by windows as it can’t get an address from the DHCP (dynamic host control protocol) indicating the router or ISP (depending on setup) is down but the DHCP client is working on your machine. If your IP address is 0.0.0.0 this can be fixed by reinstalling TCP/IP and restarting a few services – most times. If you get loss or high timings pinging local address it indicates a PC fault that needs investigation. The default gateway is normally your router, or first ‘hop’ to the internet, slow response here indicate an issue between your computer, router or ISP. Slow responses from a host online – the internet may indicate a fault somewhere between all of these and the command Tracert (trace route) comes in useful to test the path to hosts/devices. A failure to resolve hostname indicates a fault with the DNS server and will be shown as a message like ‘unable to resolve hostname’.

TRACERT

What it does –This command traces the route from one point to another

Why use it – To check the path has no delays, loss or other problems

When to use it – When you are experience delays loading pages, download issues or latency – high timings from ping results

How to use it – From a DOS Window type tracert and the target host name or IP address, examples tracert bbc.co.uk or tracert 212.58.224.85 the output of the tracert to the BBC web site is listed below(note that I have placed an X to conceal my IP address and network information, you will find correct numbers separated by dots)

C:\Documents and Settings\home>tracert bbc.co.uk

Tracing route to bbc.co.uk [212.58.224.131]
over a maximum of 30 hops:1    82 ms    99 ms    99 ms  XX.XX [XX.XX.XX.XX]
2     *        *        *     Request timed out.
3    15 ms    16 ms    16 ms  bbc-gw0-linx.prt0.thdoe.bbc.co.uk [195.66.224.103]
4    16 ms    15 ms    16 ms  212.58.238.153
5    21 ms    15 ms    15 ms  rdirwww-vip.thdo.bbc.co.uk [212.58.224.131]Trace complete.

Interpreting the results – The output from tracert shows the path taken to get to the BBC web site. The first few ‘hops’ are normally your router or ISP, then it goes outside the ISP and to the target network and if reachable the host. If you find one or two asterisks on a line with very high timings it could be the network device is busy or there may be a fault. The best thing to look for is a very little if no asterisks and low timings, as with the ping, the further away the host is geographically then the timings will increase accordingly. It can also be dependant on network infrastructure and design, examples – bottlenecks or capacity issues.

Glossary of terms and brief explanation –

• Bottleneck – in networks a design or system could reduce the flow of data in either direction depending on where it is.

• DHCP – Dynamic Host Control Protocol, basically a DHCP server assigns and controls leases of IP address to devices that use IP on a network and the DHCP client is the device requesting the IP address.

• DNS – Domain Name Service – Basically a phone book for the web, it looks up a hostname take bbc.co.uk for example then translates it to its IP address for example 212.58.224.85. You can type IP addresses into to your web browser. To find the IP address use NSLOOKUP from a DOS Window

• IPCONFIG – A command used in DOS to view IP configuration information

• PING - A command used in DOS to test hostname's or IP addresses

• TCP/IP – Transmission Control Protocol /Internet Protocol – how devices on the internet and networks communicate with each other.

NETSTAT

What it does – This command is used to view Network Statistics

Why use it – To view current connections, IP addresses, ports and other information

When to use it – In conjunction with other tests like Ping and Tracert to establish origin of fault.

How to use it and the results – From a DOS Window type netstat -a this will show you all connections, look for the ones that say established. There shouldn't be more than 15, if there are more it could be spy ware, a virus or peer to peer software making too many connections. If you use peer to peer software and have set it up to open or use quite a few connections it can degrade online performance or I have seen it grind to a halt! I suggest that Peer to Peer software is removed entirely from your computer. There are other commands that you may use, netstat -ao this shows all connections and their PID which is a process identifier this will help you to identify the program using a connection. To find the software you need to note the PID and then use Task Manager in windows. Open Task Manager (ctrl alt delete or right click task bar and click Task Manager) then on the Tab processes you may find a column PID if not click view and options tick the box for PID (Process Identifier). Click the column title/heading PID once or twice to sort ascending or descending order. Now, match up the PID from netstat with the one in Task Manager. If you don't recognise the process name, look it up on the web. If you have a firewall, the process you are looking up has access to the internet/network, if you find that after looking it up that it is a suspicious program you will need to configure your firewall to block access.