MTU: Difference between revisions

MTU (view source)

Revision as of 04:34, 15 September 2020

80 bytes removed , 15 September 2020

m

→‎What is my MTU?

AA-Andrew

autoreview, Bureaucrats, editor, Interface administrators, reviewer, Administrators

12,270

edits

Revision as of 13:37, 1 August 2017 (view source) Admin (talk \| contribs) (→‎Explanation:) ← Older edit		Revision as of 04:34, 15 September 2020 (view source) AA-Andrew (talk \| contribs) m (→‎What is my MTU?) Newer edit →
(8 intermediate revisions by 2 users not shown)
For example: [[File:Firebrick-1500MTU-ping.png\|200px\|thumb\|a 1500 ping on FireBrick]] On Linux: ping -c1 -M do -s 1472 81.187.81.187 On OSX (Apple): ping -c1 -D -s 1472 81.187.81.187▼ On Windows: ping -n 1 -f -l 1472 81.187.81.187▼ ^^ That's the ping command to remember. The rest of this section is a bit of info about that command. ==Explanation: of the ping options== '''-c1~~'''~~ In ~~these~~/ ~~examples,~~-n we1'''ve ~~only~~This ~~used~~is aoptional, ~~count~~it ofsimply ~~one~~tells ping ~~using~~just ~~the~~to -csend ~~option.~~a single ping '''-M do / -f / -D''' The important option! This means don't fragment the ping packet - we don't want the ping split into multiple packets when testing MTU! ~~'''-M do''' Use the path discovery options to ping. The option is -M. See the man page for all the options.~~ ''' -s 1472 / -l 1472''' The ~~option for~~ payload size ~~is -s~~. When setting size in ping, the size ~~printed~~ is the payload size - not the full packet size. '''The full packet size is''' <syntaxhighlight inline> payload (1472) + IP header (20) + ICMP header (8) </syntaxhighlight>, so this is 1500 in total! ~~Note: ping is slightly different on different operating systems, the above is a Debian machine.~~ ~~On OSX (Apple), to perform a ping with the same options, you can use:~~ ▲ ping -c1 -D -s 1472 81.187.81.187 ~~On a Windows machine to perform a ping with the same options, you can use:~~ ▲ ping -n 1 -f -l 1472 81.187.81.187 ==Two quick examples== This is despite the bridging modem used for the tests not claiming to support an MTU > 1500 octets and with PPPoE needing to send 1504 octets and receive 1508. ] [[Category:MTU]]