Member Avatar for gateclaw

I saw a few posts similar to this in this forum.I tried most of the solutions given there but still couldn't solve my problem.
I'm running XP Professional on my laptop and desktop.Both are connected to internet using the same connection through lan.The problem is that I can't access some sites on my laptop while there is no problem whatsoever on the desktop.I tried disabling the firewall,running in safemode,using opendns,different browsers like IE7,Firefox,Opera etc but no use.Plzz help.
Some of the sites I cant access are microsoft.com,download.com.

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A few extra, practical notes on the exact problem that appeared here (some sites reachable from one machine but not another) and how to diagnose or avoid it in future. Several good checks were already suggested by the community — hosts/proxy checks from , scanning and firewall removal from and , and the short-URL/ISP test idea from — but the root cause in this thread was a path-MTU-related mismatch. That explains the “Waiting for …” hang and why only some sites failed.

Why it happens: path MTU discovery (PMTUD) uses the IP DF flag and relies on routers sending ICMP “fragmentation needed” messages. If an intermediate link (PPPoE, VPN, ISP tunnel) has a smaller MTU than your Ethernet and either the path or your firewall blocks the ICMP messages, large packets are dropped and the remote server never learns to send smaller packets — pages stall or never complete. See Cisco’s PPPoE/MTU explanation and the general PMTUD description. (cisco.com)

How to test and fix (safe checklist)

  • Test the path MTU with iterative pings that set the “don’t fragment” bit, then add 28 bytes to the largest working payload to get the MTU. Example commands:

    C:\> ping -f -l 1472 example.com
C:\> tracert example.com
C:\> netsh interface ip show interface

    Reduce the ping payload until it succeeds, then add 28 to compute MTU. Instructions and rationale for the ping method are documented here. (support.itel.com)

  • On Windows XP you can view interface info with netsh interface ip show interface (you may need Routing and Remote Access started). XP does not expose a convenient GUI MTU change; Microsoft’s KB shows safe registry edits for PPP/VPN MTU or use an OS-appropriate tool. Back up the registry before editing. (superuser.com)

  • Best fixes: adjust the MTU/MSS on the router/ADSL/PPPoE endpoint (or enable MSS clamping on the WAN device) so endpoints don’t need manual per-PC changes. If a third‑party firewall/VPN is installed (like Kaspersky or similar), fully uninstall or disable its network driver while testing — such software sometimes blocks ICMP or alters MSS. For authoritative notes on changing MTU and PPPoE behavior see Microsoft and Cisco docs. (learn.microsoft.com)

Cautions: avoid guessing MTU values — measure with the ping method first. Always back up the registry and router config before making permanent changes.

Recommended Answers

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Member Avatar for coolraj003

Have you tried fiddling withthe settigs in the internet options to see if they let you access the sites?

What does the error message say when you try to access them?

Raj

Member Avatar for skumarnpglobal

Try to open these sites with tinyurl.com if sites opened then there is a problem from your ISP side. Otherwise if running in Laptop but not in Desktop then you have to either check third party software/Firewall or browsers restricted sites zone area.


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Member Avatar for jammiedude

have you ever had any previous firewalls installed?

Member Avatar for gateclaw

Have you tried fiddling withthe settigs in the internet options to see if they let you access the sites?

What does the error message say when you try to access them?

Raj

There is nothing wrong with the internet options i suppose..
There is no error message shown..When i type the url, the status bar shows "Waiting for blahblah.com" and there's this blank screen where nothing shows up.As I told this problem is with certaqin sites only.
Actually the problem is worse now.I can't even access this forum from my laptop(which i was able earlier when i posted the first time)..

Member Avatar for gateclaw

have you ever had any previous firewalls installed?

i had kaspersky firewall earlier,but currently disabled it.

Member Avatar for coolraj003

Have you tried to scan your laptop for any possible infection? ALso would be advisable if you could have alook at the windows firewall as well mate.

Raj

Member Avatar for gateclaw

Have you tried to scan your laptop for any possible infection? ALso would be advisable if you could have alook at the windows firewall as well mate.

Raj

well i scanned with the latest updates of kaspersky and found nothing.also tried disabling windows firewall.still hopeless:(

Member Avatar for Tim.Sage

Have you checked your hosts file?
It is located in WINDOWS\system32\drivers\etc and can be opened with notepad. it should just have a couple of entries in it.

And you could check for any proxy settings set up on your computer.

Member Avatar for jammiedude

Try uninstalling kaspersky completely, i have had problems with previous firewalls, particulary norton which i thought was not enabled but after uninstalling worked fine. When you tried firefox did you import any settings from internet explorer? Also run tracert on the specific sites that you cant access and see if there is a certain point at which it stops.

What type of sites are they are they http, or https?

Member Avatar for gateclaw

sorted out the problem guys..the mtu value was changed to 1492.set it back to 1452 and no more problems.can some application cause this change coz i dont remember playing with this value?
anyway thanks for ur replies.:)

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