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Note: All the posts are based on practical approach avoiding lengthy theory. All have been tested on some development servers. Please don’t test any post on production servers until you are sure.

Wednesday, March 21, 2012

Simple Network Tests



Some times there is slowness in network and end users face it but complaining about the database or application. We can use some initial testing for such network slowness.

Test the loop-back address. Type ping 127.0.0.1. It is the same for every computer, so you do not need to change this. This will test your computer's network chip. Keep an eye on the response time, as it represents the connection's latency between you and the server. Double digit values, such as 50ms, is very good.

C:\Documents and Settings\inam>ping srv1 -n 10
C:\Documents and Settings\inam>ping srv1 -t  [CTRL +Break , CTRL+C]

Test your local Gateway. Find your Default Gateway's IP address:
Type ipconfig in the command prompt  (cmd) window. Find the listing for "Default Gateway". This is the IP you can use in a ping to test the connection between your computer and your router or ISP.

Check Domain Name Resolution. Instead of an IP address, type in a site's domain name, such as www.google.com. Pinging a domain name tests your computer and network's ability to resolve network names (translating them to IP addresses).

Measure network and Internet performance (Windows NT, 2000, XP, and Vista only). Use the tracert command to measure the response of each hop in a network path. Your connection to any one server will require multiple "hops" between other servers and networking components. The fewer number of hops, the better. Most connections to a server on the Internet will include at least a dozen hops. To test:

C:\Documents and Settings\inam>tracert srv1

Tracing route to srv1 [10.10.2.179]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  172.55.20.254
  2     1 ms     1 ms     1 ms  192.168.181.237
  3     3 ms     2 ms     2 ms  192.168.181.242
  4     2 ms     2 ms     2 ms  192.168.200.9
  5     2 ms     2 ms     2 ms  10.10.2.179

Trace complete.You only need to replace network cards and cables if there are serious delays on the first hop.
Other things on your home or work network could be causing packet storms. A looped back cable on your router or switch will cause slow connections or even stop the network. If you are wireless, signal strength is the biggest factor. Other things like badly configured DHCP or manual settings on your network connection can cause slowdowns too. The wrong or a slow responding DNS server will cause serious lag with the first hop.


Pathping – Test Network Latency
Windows based command line tool that provides information about network latency and packet loss between a source and destination address.
Pathping is a great tool for determining which intermediate device may be having network problems.


PathPing Network Connectivity Testing
Pathping uses the ICMP protocol to test for network issues. This is done by sending echo requests and analyzing the results. Pathping will send multiple echo request messages to each router in along the path to its destination. Depending on your network you may have several routers or just a couple. Pathping will test each router and analyze the results for latency and packet loss.

C:\Documents and Settings\inam>pathping srv1

Tracing route to srv1 [10.10.2.179]
over a maximum of 30 hops:
  0  oamr-pc3 [172.55.20.101]
  1  172.55.20.254
  2  192.168.181.237
  3  192.168.181.242
  4  192.168.200.9
  5  10.10.2.179

Computing statistics for 125 seconds...
            Source to Here   This Node/Link
Hop  RTT    Lost/Sent = Pct  Lost/Sent = Pct  Address
  0                                           oamr-pc3 [172.55.20.101]
                                0/ 100 =  0%   |
  1    0ms     0/ 100 =  0%     0/ 100 =  0%  172.55.20.254
                                0/ 100 =  0%   |
  2    9ms     0/ 100 =  0%     0/ 100 =  0%  192.168.181.237
                                0/ 100 =  0%   |
  3    7ms     0/ 100 =  0%     0/ 100 =  0%  192.168.181.242
                                0/ 100 =  0%   |
  4    5ms     0/ 100 =  0%     0/ 100 =  0%  192.168.200.9
                                0/ 100 =  0%   |
  5    5ms     0/ 100 =  0%     0/ 100 =  0%  10.10.2.179

Trace complete.

A 0/100 = 0% means that out of 100 packets, none were lost. A low single digit loss 1% or 2% is common, but anything higher is an indication of a network issue.

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