There is this peculiar problem I'm facing with MTU settings.
I'm using PPPoE with wifi enabled on Windows 8.1.
Couple of months back:
* ADSL MTU setting was promptly set to 1492 (8 bytes for PPPoE header discounted).
All of a sudden, yahoo mail was not accessible.
When I tried
Packet size of 1464 (MTU:1492 - 28 bytes for adjusting different header size) is big. So decided to change MTU.
I checked for various packet sizes; First ping was OK for packet size of 1452. So MTU can be set at 1480.
I changed the MTU to 1480 in modem setting and restarted.
When connected, I tried yahoo mail again - and again failed.
I checked the MTU which is set at 1480. I tried ping with packet size of 1452 and got surprise. I got "Packet needs fragment" again. The same size was working earlier.
I repeated the process. Now the MTU came to 1460. I set the MTU again in modem and restart and try yahoo mail again to get the same failure.
Again I ping with packet size 1432. Nope. Got "Needs fragment" error.
Changed MTU setting in Modem to 1400 - retry cycle - same issue.
Changed MTU setting in model to 1300 - retry - same issue.
Then I came across setting MTU for interfaces in PC.
So reverted the MTU to 1492 in modem.
Set the PC interface MTU as below. I set it for WiFi interface as I was using wireless Internet access.
This solved the problem and I was happy.
Fast forward to current day.
Today I couldn't access yahoo mail.
Checked the MTU setting for PC wifi interface. It has been reverted to 1500 (default). May be some windows update did that.
I set it back to 1460. Tried to access yahoo mail. Still not accessible.
Checked the ping with size of 1432 (for MTU 1460). Got "Needs fragment" error.
Checked ping with packet size 1400 - OK - change interface MTU to 1420 - Still couldn't access yahoo.
Checked ping with pkt size 1400 - now not OK.
Checked ping pkt size 1360 - OK - Change interface MTU to 1300 - still couldn't access yahoo mail.
Checked ping pkt size of 1360 - now not OK.
This seems to be vicious cycle.
Any one has an idea what is happening?
I'm using PPPoE with wifi enabled on Windows 8.1.
Couple of months back:
* ADSL MTU setting was promptly set to 1492 (8 bytes for PPPoE header discounted).
All of a sudden, yahoo mail was not accessible.
When I tried
Code:
ping -f -l 1464 mail.yahoo.com
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
I checked for various packet sizes; First ping was OK for packet size of 1452. So MTU can be set at 1480.
I changed the MTU to 1480 in modem setting and restarted.
When connected, I tried yahoo mail again - and again failed.
I checked the MTU which is set at 1480. I tried ping with packet size of 1452 and got surprise. I got "Packet needs fragment" again. The same size was working earlier.
I repeated the process. Now the MTU came to 1460. I set the MTU again in modem and restart and try yahoo mail again to get the same failure.
Again I ping with packet size 1432. Nope. Got "Needs fragment" error.
Changed MTU setting in Modem to 1400 - retry cycle - same issue.
Changed MTU setting in model to 1300 - retry - same issue.
Then I came across setting MTU for interfaces in PC.
So reverted the MTU to 1492 in modem.
Set the PC interface MTU as below. I set it for WiFi interface as I was using wireless Internet access.
Code:
netsh interface ipv4 set subinterface "Wi-Fi" mtu=1460 store=persistent
Fast forward to current day.
Today I couldn't access yahoo mail.
Checked the MTU setting for PC wifi interface. It has been reverted to 1500 (default). May be some windows update did that.
I set it back to 1460. Tried to access yahoo mail. Still not accessible.
Checked the ping with size of 1432 (for MTU 1460). Got "Needs fragment" error.
Checked ping with packet size 1400 - OK - change interface MTU to 1420 - Still couldn't access yahoo.
Checked ping with pkt size 1400 - now not OK.
Checked ping pkt size 1360 - OK - Change interface MTU to 1300 - still couldn't access yahoo mail.
Checked ping pkt size of 1360 - now not OK.
This seems to be vicious cycle.
Any one has an idea what is happening?
My Computer
System One
-
- OS
- Win 8.1 64 bit
- Computer type
- Laptop
- System Manufacturer/Model
- Lenovo L530
- CPU
- i5 3230M @ 2.6 GHz
- Memory
- 4GB