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I have a weird problem that started recently (last few weeks) - on my home network 1 pc has problems browsing web sites (although ping is usually not an issue ~1% lost, is probably fine for wireless, although I don't remember having that in the past). I have 2 more laptops with win7 and they work fine.

Now the wierd part: from past experience I know that this could be caused by MTU settings, so I checked it with "ping -f -l" and found a problem ("... but DF set"), so I lowered MTU (using netsh) from default 1500 to 1472 and it seemed to solve the problem. For a few hrs. Then I checked again and 1472 was no longer working (using the same ping command) so I went down to 1400 (confirming that it works with ping). This helped for another couple of hrs. I checked with ping again and 1400 was bad. I went down to 1200 and downloaded mtupath app. It showed that working setting is 1200. But now it doesn't work again >_<

And I'm typing this text from another laptop in the same wifi network that has win7 and default MTU setting 1500. And mtupath believes that's fine:


MTU path scan to (, ttl=64, limit=48
# 16 processing - best MSS 1472 (estimated MTU 1500) [pPPPPpPppPpppppp]
# 01 nearest minimum MTU on local interface

        #1 MSS IN RANGE     1 <==  1471 ==>  1472
        #2 MSS EXCEEDED  1473 <== 14911 ==> 16384

So I was wondering if anyone has any idea what setting (I presume that's smth related to wifi) could cause such problem.

My net config is cable box (adsl) in pass through mode, wifi router (rt-n56u) in NAT mode, then ~10 devices connected to it.

All computers have MS Security Essentials installed.

Some wifi stats from my router:

MAC address : 14:DA:E9:F9:64:D0
OP Mode     : AP
Phy Mode    : 11b/g/n
Channel     : 13

Stations List              
MAC               PSM PhyMode BW  MCS SGI STBC Rate Connect Time
Not Working F4:6A NO  HTMIX   40M 14  NO  NO   243M 01:53:32
Working fine 7:54 NO  HTMIX   40M 7   NO  NO   135M 00:29:10
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This was caused by 2 factors:

  1. loosely connected antenna on the wifi card
  2. energy saving setting on the card set to max saving

MTU not related

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