About MTU Size

A

Anil

asking & answering?
Messages
478
Location
Hyderabad, India
ISP
ACT Fibernet,JioFiber,BSNL
hi til now I thought that the maximum size of MTU is 1472 bites as 28 bites is taken of for some technical useage
but today I tested MTU ping results with ACT Fibernet
the CMD was able to ping up til 1472 bites
how!
acording to many articals on the web it should not.
I should bee able to ping only upto 1464 bites
I wonder can any one help me with this?
@Sushubh
 
The standard MTU for ethernet is 1500 bytes. Since ACT uses PPPoE connection, the encapsulation uses 8 bytes and your MTU will be 1492. Where did you get the 1472 number from?
 
8 bytes for PPPoE and the other 28 for TCPIP and IPv4 packet headers?
 
hear is the ping result
with MTU Size of 1472 bites
Microsoft Windows [Version 10.0.17763.475]
(c) 2018 Microsoft Corporation. All rights reserved.

C:\Users\>ping google.com -f -l 1472

Pinging google.com [172.217.163.142] with 1472 bytes of data:
Reply from 172.217.163.142: bytes=64 (sent 1472) time=17ms TTL=57
Reply from 172.217.163.142: bytes=64 (sent 1472) time=16ms TTL=57
Reply from 172.217.163.142: bytes=64 (sent 1472) time=17ms TTL=57
Reply from 172.217.163.142: bytes=64 (sent 1472) time=16ms TTL=57

Ping statistics for 172.217.163.142:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 16ms, Maximum = 17ms, Average = 16ms

C:\Users\
 
what happens with ping google.com -f -l 1492 ?
 
Great !
so you can set the max by checking the highest number...
 
it is not A problem for me
I never seen MAX MTU of 1472 before
so i wondered and asked how can it bee?
any way my router is set to automatic IP
MTU size is controled by ACT Fibernet
 
ideally set it to max after doing few tests or ask the isp if they understand....
 
in adsl it is 1492 (1464 + 28)
in ethernet it should be 1500 (1472+28)

do a test
ping broadbandforum.co -f -l 1464
ping broadbandforum.co -f -l 1472

where the 1464 is the value before adding 28 bits for adsl
where the 1472 is the value before adding 28 bits for ethernet based service provider.

If you using hotspots, i found airtel uses 1500 mtu
Vodafone uses 1020 mtu
Jio uses 1500 mtu

Can you guys help me with your hotspot values....
 

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