India Broadband Forum

aray

For the last several days (2+ weeks now), I am facing a strange problem in Dataone connection. While some sites are opening, some other sites are not opening or taking an abnormally long time to open up. But when I do a speed test via Calcuttatelephones / SpeedTest, I find good upload/download speed.

Even, I had problem to access this forum a few minutes back. When I rebooted the Router and the PC then I was able to access this forum (at least I can now be able to seek help here ), but at the same time sites like Hotmail, Google are now not accessible now.

My Configuration :
OS : Ubuntu Intrepid (up-to-date updated)
ADSL 2+ Router from D-Link GLB-502T
Other : I have connected the BSNL line direct to the Router. I am also using a D-Link Switch so that I can use the same connection in my other system (which I rarely use).

In the Network settings on Ubuntu the connection is set as auto eth0 (just a small note here - I tried to change this auto setting to manual but it did not worked. So in case I am suggested to make any changes in the network setting, may be you have to suggest me how to do it directly though the system files).

I contacted BSNL people, who suggested me to try a different DNS settings, which worked for a day but then again the problem is happening. I also tried few things like changing MTU settings to 1200, opendns etc., but still the problem is there.

Please help me as this problem is really not showing signs of improvement.

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I am using Unlimited 750+ plan.

totallyfandu

just remove the dns and put it in auto mode and then try

just u all tell me one thing why we are using DNS and if we are not putting any dns then whether their any problem or not

thanks for that but i never find any difficulty in any site and i never put DNS and i am using bb from last two years so why we enter DNS

according to me it change address into ip only this as a result of which sites open fast only this.

thanks for ur reply

i lso not geeting ping i just check on my pc th i am geeting same
ping calcuttatelephones.com -t [210.212.0.250] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
but i am able to open the site so what the problem cool_techie_tvm

tell me i am unable to understand that i am not geeting ping but able to open site and i am not using any dns

thanks for ur reply

cool_techie_tvm

MTU at 1200!! Great Scots...try 1492. Messing with MTU and assigning lower values will greatly hamper your internet experience.

Edit : Use http://www.tek-tips.com/faqs.cfm?fid=1995 to find your connections MTU value.

cool_techie_tvm

Call me lazy but i am posting wikipedia entry for your first query. Domain Name System - Wikipedia, the free encyclopedia

The author says he is able to browse the internet, but only some sites are inaccessible. It means the DNS is functioning properly. Also he seems to have altered the default MTU of 1500.

Answering the second part of your query, if DNS is not mentioned, then the OS takes the IPs listed in the router (which will be DNS received from BSNL automatically)

cool_techie_tvm

Like mentioned in the post the DNS is automatically retrieved from BSNL. BSNL DNS servers are fine as long as they work, but sometimes the server is subjected to overloads and hence becomes unresponsive and this will inturn affect the end user (his browsing experience will be dampened). Thats why people opt for professional DNS services from OpenDNS and DNSAdvantage.

aray

Many thanks to everyone for helping. Now I will try to explain few things here as per my understanding.

Regarding MTU when I make 1492 (default), I am not getting the connection at all. So I had to make 1452, which is helping to browse the Internet. About the Value of 1200, it was suggested only by by D-Link support and it remained at 1200 for long time, when everything worked perfectly for me.

About the DNS, I have not made any changes and it is now auto. So at present the status is :

MTU : 1452
DNS : Auto

Some details from ifconfig :
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1968 errors:0 dropped:0 overruns:0 frame:0
TX packets:2208 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1433816 (1.4 MB) TX bytes:288202 (288.2 KB)
Interrupt:20

Status : I am now being able to browse normally. Google, Hotmail etc. are working correctly.

But I am quite sure (as this has been happening almost daily), tomorrow again when I start the problem will again start happening. Because with the above settings, I have been facing problem too.

cool_techie_tvm

Did u checkout How to find max packet size for DSL, Cable, etc. - TCP/IP FAQ - Tek-Tips ? And try experimenting and ultimately finding the MTU for your connection? Agreed that D-Link support mentioned 1200, but still i think you should so the MTU experiment.

aray

Many thanks cool_techie_tvm for the link and also for helping me. This is a great support for me. I was feeling helpless with every passing day and no solutions in sight.

Yes, I did tried with changing the MTU by reducing it with a margin of 10 (as advised by many). That gave me a value of 1452. As I said earlier this 1452 looks good. But being a person without any understanding of Networking, I have few questions here :

a) Once I get a correct MTU will it work always (at least for a long time 2-3 months) or do I have to change it everytime I log in to my system? Because that is what happening most of the time.
b) When I do a : ping 4.2.2.1 (as suggested in the link), I get request timed out. But if I do : ping 192.168.1.1 it works correctly (0% packet loss).
c) Please find below some of the ping results that I am getting (in Vista) :
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>PING -f -l 1492 calcuttatelephones.com
Ping request could not find host -f. Please check the name and try again.

>PING calcuttatelephones.com

Pinging calcuttatelephones.com [210.212.0.250] with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.

Ping statistics for 210.212.0.250:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Please note, I am getting Calcuttatelephones.com when trying from browser.

>PING -f -l 1492 google.com
Ping request could not find host -f. Please check the name and try again.

>PING google.com

Pinging google.com [209.85.171.100] with 32 bytes of data:
Reply from 209.85.171.100: bytes=32 time=318ms TTL=234
Reply from 209.85.171.100: bytes=32 time=319ms TTL=234
Reply from 209.85.171.100: bytes=32 time=319ms TTL=234
Reply from 209.85.171.100: bytes=32 time=318ms TTL=234

Ping statistics for 209.85.171.100:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 318ms, Maximum = 319ms, Average = 318ms

>PING -f -l 1492 bsnl.net.in
Ping request could not find host -f. Please check the name and try again.

>PING bsnl.net.in

Pinging bsnl.net.in [61.0.0.121] with 32 bytes of data:
Reply from 61.0.0.121: bytes=32 time=97ms TTL=61
Reply from 61.0.0.121: bytes=32 time=97ms TTL=61
Reply from 61.0.0.121: bytes=32 time=97ms TTL=61
Reply from 61.0.0.121: bytes=32 time=97ms TTL=61

Ping statistics for 61.0.0.121:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 97ms, Maximum = 97ms, Average = 97ms
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I tried the above PING -f -l command (from Vista) with different values but it's not working. Strangely though when I try the ping command from Ubuntu it works to some extent :

$ sudo ping -M do -s 1424 google.com it returns :
64 bytes from google.com (72.14.205.100) L icmp_seq=16 ttl=240 (tuncated)

If you need to know any further details, please ask, I will be happy to provide it.

I only wish this problem finally solves.

cool_techie_tvm

Yes once u get the correct value, u should enter it in the modem settings and save it. Thus it need not be entered again and again.

Ping not working with 4.2.2.1 (which is level 3's DNS server) maybe attributed to improper DNS resolution/routing. But the same working in internet browser is what which baffles me. Because if it is indeed a DNS problem, then u should not be able to open up the websites in browser too. It seems like the TCP/IP architecture of the OS is currupted since u are facing no such problems with Ubuntu on the same connection.

Also make sure the firewalls (both in router and OS) is disabled. Dlink has integrated firewall which disallows ping, tracert.

cool_techie_tvm

Ping is used to verify whether a particular host is reachable. It uses specialised ICMP echo commands for sending and recieving. One of the common problem of ping not working as desired is because it is being filtered at the firewall. Since the http port used for browsing is always allowed in firewalls, the site may open up in the browser.

sanluvz

im having some problem. websites are not opening.
which dns should i use?
how to change to opendns?

cool_techie_tvm

Checkout https://www.opendns.com/smb/start/

rupu1983

Yes also i have faced this problem few times now few sites are not opening i changed opendns few times but problem still present.

cool_techie_tvm

Verify the MTU value has been correctly configured in the OS or router (according to the mode of connection). For bridged mode MTU must be changed in OS and for router/pppoe mode MTU must be saved in the router.

Use How to find max packet size for DSL, Cable, etc. - TCP/IP FAQ - Tek-Tips to find max MTU

sanluvz

PING –f –l 1492 Your Internet Provider's URL

whats d url?

cool_techie_tvm

U can try any URL from the following.

PING –f –l 1492 Google
PING –f –l 1492 Yahoo!
PING –f –l 1492 Bharat Sanchar Nigam Ltd.- India's No. 1 Telecommunications Company

aray

Thanks cool_techie_tvm.

Yes you are correct. D-link Firewall is on. If I off it will there be any security concern or not?

For now I am going to off it and respond to you soon.

BTW, for now the Internet connection is working well.

cool_techie_tvm

Welcome mate!!

Disabling firewall will allow spyware/trojans to enter the pc. But something robust like KAV, Norton 2009 should keep the nastiness at bay.

Nice to know the problem is solved at last. Enjoy

aray

Sorry cool_techie_tvm, it was just a temporay relief, just 10 minutes. Again Hotmail is not working, suddenly everything went very slow. While some sites are opening some are not.

In Hotmail I noticed, while I reached the Sign In page and entered login details then the next page (i.e. the inbox page) is not coming. It is showing "waiting for <.... URL .... >

As I mentioned earlier this is the way how it is going on for the last so many days.

With regard to firewall eveything was working perfectly till December about 3 weeks back, even with D-Link firewall on.

One more info : All the four lights in router is glowing green correctly.

cool_techie_tvm

Have u tried opening up the same in Ubuntu? This seems like an OS related problem.