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Able to ping websites; but not able to browse websites.

Posted on 2011-05-03
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Last Modified: 2012-05-11
We have 2 mbps internet leased line at our office.

Sometimes in day, users in our office are not able to browse websites(get page cannot displayed) in browsers, but we are able to ping websites. But this problem resolves automatically on its own.
Even outlook mailbox works fine and yahoo messengers remains connected but web browsing doesn't work.

I don't understand where problem is.

Network setup:
All Systems in work group environment.
Cyberoam C25i Firewall
and Dlink 48 switch.
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Question by:VINOD MORE
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28 Comments
 
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Expert Comment

by:The_Kirschi
ID: 35511979
Don't know if yahoo messenger uses http(s) but could it be that there is a limitation on the number of http(s)-connections on the firewall that will block new connections if the limit is reached until some connections are released?
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Author Comment

by:VINOD MORE
ID: 35512024
@ The_Kirschi

I am not bothered about yahoo messenger; it connects or disconnects i said what observed when this thing happens.
Its highly unlikely; that's its reached beyond maximum connections because there are hardly 7~8 users in our office.
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Accepted Solution

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The_Kirschi earned 1125 total points
ID: 35512075
How long does the problem persist each time? Maybe there is some caching mechanism somewhere "between" you and the websites that cleans itself up and connect does not work during cleanup? Do you get any error message in your browsers?
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Author Comment

by:VINOD MORE
ID: 35512233
The_Kirschi
It remains till 4mins to 10mins may be; actually never noticed it.

Do you get any error message in your browsers?
-- No normal page cannot be displayed message comes.
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Assisted Solution

by:The_Kirschi
The_Kirschi earned 1125 total points
ID: 35512446
Well, that is really strange. Obviously the internet connection is fine and if you can ping the websites then also DNS seems to be working, assuming you don't ping by IP. So in my eyes it must be an issue with http/https. Are sure there is no proxy and/or caching mechanism involved? Are you connected with the Cyberoam directly to your ISP or is there some other router involved? Can you access any logs on the firewall?
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Author Comment

by:VINOD MORE
ID: 35556885
@ The_Kirschi

issue with http/https
--- I didn't get this. Can u explain me.

Are sure there is no proxy and/or caching mechanism involved?
--- Its simple network set up no Domain, no Proxy server, no mailserver.

Are you connected with the Cyberoam directly to your ISP or is there some other router involved? Can you access any logs on the firewall?
--- Cyberoam itself is functioning as router no router in between. Logs, don't know how to check. I'll try.


Network diagram attached


Untitled-1.jpg
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LVL 16

Assisted Solution

by:The_Kirschi
The_Kirschi earned 1125 total points
ID: 35687717
Well, http and https are the protocols that are used by a webbrowser to access webpages.

Ping for example uses icmp.

So there must be something that cuts off your http/https traffic for the time of interruption. But from your network diagram I cannot find where that should be except that one could have a look at the firewall logs. I have never heard of Cyberoam firewall so I don't know how to access log files or configuration there.

Maybe this pdf helps you though it's quite old (2007):

http://docs.cyberoam.com/redirfile.asp?id=155&SID=

Or have a look at docs.cyberoam.com
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Author Comment

by:VINOD MORE
ID: 35688299
Do you think it would be problem with Cyberoam? I don't think so, cause with same settings and same device everything was working fine.

Also shall I try connecting a laptop directly to ISP modem and check out?
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Author Comment

by:VINOD MORE
ID: 35688338
Hope some more experts jump in this topic and help me.
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Expert Comment

by:The_Kirschi
ID: 35688371
Maybe you should click the "Request attention" link in your question section at the top to ask for other experts. Sorry to not be of more help.
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Expert Comment

by:remixedcat
ID: 35688611
Please try directly connecting to the ISP connection with your laptop to isolate.

Please check your firewall settings.
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Author Comment

by:VINOD MORE
ID: 35688660
@ remixedcat

laptop to isolate
--- Isolate Cyberoam UTM?

Please check your firewall settings.
--- Firewall settings i doubt there would be any problem. Still i will check.
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LVL 11

Expert Comment

by:remixedcat
ID: 35688672
yes to isolate whether the firewall is the problem and not the ISP.if it is then the settings need changed.
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Assisted Solution

by:Jordanlcn
Jordanlcn earned 375 total points
ID: 35688699
Issues like this is normally on the firewall/router.  What are the features of cyberoam.  By your diagram the only thing that can cause this issue is the firewall.  it might be doing cache with out you knowing and running out of memory.  Also the page cannot be displayed error are you sure its not Page Time out.  This also happens when someone is maxing out the bandwidth (ie. Downloading, Torrents, ect...)

Ill do some reserach on the firewall you have since I am not familiar with it.  but if you can post some items about its features and capabilities that helps a lot.  Is this a Hardware Appliance Firewall/Router?
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Expert Comment

by:The_Kirschi
ID: 35688710
My talking...
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Author Comment

by:VINOD MORE
ID: 35688737
@ Jordanlcn

Is this a Hardware Appliance Firewall/Router?
--- Its hardware device, actually its UTM(Unified Threat Management) device.
More info here www.cyberoam.com
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Author Comment

by:VINOD MORE
ID: 35688785
@ The_Kirschi

My talking...
--- ??
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Expert Comment

by:The_Kirschi
ID: 35688892
I meant that was just what I was saying in my comments above. Maybe I just did not make myself clear enough.
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LVL 37

Expert Comment

by:bbao
ID: 35689584
does TELNET to the web server by name or IP on port 80 work?? for example:

TELNET www.google.com 80

or

TELNET 66.102.11.104 80
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LVL 3

Expert Comment

by:Jordanlcn
ID: 35689913
Is this how your firewall Admin page looks like?
Cyberform.jpg
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LVL 1

Author Comment

by:VINOD MORE
ID: 35690898
@ bbao
I will check when problem occurs.

@ Jordanlcn
Ya, more or less same.  But image taken is of high end version of Cyberoam with more features.
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LVL 30

Expert Comment

by:ded9
ID: 35696916
It clearly points to a dns issue. Check the dns settings in your isp modem..that should fix your problem.
I hope this problem occurs in all the computers that are connected to the modem.

Can try  open dns for a day to find out whether its a dns issue.

www.opendns.com

208.67.222.222
208.67.220.220



Ded9
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LVL 3

Expert Comment

by:Jordanlcn
ID: 35698447
Looking at the features of your Router/Firewall.  When this happens again look trough the reports and see if there is anything that is eating up your network.  Its easy to fill up a 2Mbs link.  All it takes is 1 torrent and blocking it.

Check your reports and see what is happening during this time.
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Author Comment

by:VINOD MORE
ID: 35699553
@ ded9

Not an DNS problem i guess, cause tried websites with ip address.
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Expert Comment

by:The_Kirschi
ID: 35699670
if you try ip, then dns is not involved. try ping websites by name. if that does not work during the problematic periods then it is dns
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LVL 30

Expert Comment

by:ded9
ID: 35700390
I would recommend trying the step as it wont break anything....remember your old dns setting before making changes.


Also i would recommend booting the computer in safe mode with networking before changing the dns. If you do not have the problem is safe mode with networking then the problem is caused by a software or driver that runs at startup.


Ded9
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LVL 1

Author Comment

by:VINOD MORE
ID: 35718044
Will have to wait till problem occurs again.
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Author Closing Comment

by:VINOD MORE
ID: 35752251
Since its not complete solution.
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