network lag and drops

Posted on 2011-09-26
Last Modified: 2012-05-12
I have found that the occasional webpage will disconnect (seen in attached picture).  Can this be caused by DNS lookup issues?

If so, where do I look on the domain controller for these issues?  (I mean, specifically as I have looked within the reverse and forward lookup zones, and I'm a bit over my head on this one)

Also, I have noticed that when the browsers do what is seen in the image, pressing F5 (refresh) typically makes the page work (nearly 100% of the time). dropped packet, or DNS problem?
Question by:mgedlaman
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Expert Comment

ID: 36616020
If the working/nonworking/working behaviour you describe is all in the same session, it's not likely to be a DNS resolution problem.

- What does the "More information" link report?
- When you say "disconnects", do you mean that some page with auto-refresh suddenly fails as in the image you attached?  Or do you mean that when you click on a link you get the error?
- If you try immediately after it fails, does it work right away or only after some time elapses?
- Are you behind a web proxy server?  Do you have access to its logs?
- Is it always the same WWW server?
Here are my typical steps for network troubleshooting WWW connections.  In general:
- Eliminate the web browser, especially if it's MS Internet Explorer.  I'm not being bigoted here, it's just that MSIE hides/simplifies things so much that troubleshooting is more difficult.
- Test IP connectivity
- Test TCP connectivity
- Test name resolution
The following specific commands asssume IP and DNS name "".  Note that in all cases, a firewall at your site or the server's site can affect results.

ipconfig /flushdns

If this doesn't return the IP address you expect, the problem (at least part of it) is name resolution.

If this doesn't work, you either have basic IP-level connectivity problems, or a firewall is blocking ICMP echo requests, or the site itself doesn't respond to ICMP echo requests.

telnet 80
Note that the MS telnet client also simplifies things too much.  If the command works, your Command Prompt window will clear and you'll have a blinking cursor at the top left.  Type <CTRL>-] then "quit"<ENTER> to exit the telnet client.  If instead you see something like "Could not open connection to the host, on port 80: Connect failed" very quickly, the site's HTTP server isn't running (or a firewall is refusing the connections).  If there's a longer delay followed by the same message, the site is dropping requests (or a firewall is blocking you).

telnet 80
If this works, neither DNS nor TCP-level connection is the problem.  It may be the web server's configuration.

Within a non-MSIE browser (if possible), enter URL "".  The response is server-dependent, but hopefully indicates whether the problem is that the site doesn't exist, or some larger problem.

Author Comment

ID: 36912441
Thank you klode!

Its from all computers connected to the domain.  It is not one particular webpage, but no particular tendancy as far as that goes (any webpage).  

I have noticed a tendency for one of our 24 port switches to do ping commands like:


then it will repeat that rollercoaster.  My lead administrator has asked me to connect directly to the switch, and perform testing (i.e. remove one cable at a time while the ping command is running) to rule out one particular connection problem, then after that, while everything is removed, I will then RMA the switch, does that sound like the correct procedure?

I'd like to find the actual problem, but if this is what's causing it, then I'll just go with the flow as it were.

Accepted Solution

mgedlaman earned 0 total points
ID: 36996824
Turns out it was the DNS server was pointing to an old DNS address that was not updated when the ISP updated the service :P

Author Closing Comment

ID: 37016646
Problem resolved itself

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