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read the transcript!
ping checks if you can reach a host and how long the host took to reply
$ping health.gov.au
output:
... time=253ms...
Australia is 17,000 km from me. at the speed of light it’s still far!
ping works by sending an ICMP packet and waiting for a reply
ping: to: health.gov.au hello!
health.gov.au: I’m here!
myth: if a host doesn’t reply to ping, that means it’s down
Some hosts never respond to ICMP packets. This is why traceroute shows “…” sometimes.
ping: hello!
host (thinking): not listening!!
traceroute tells you the path a packet takes to get to a destination
me → my ISP → NYC → Sacramento → Australia
example traceroute
$ traceroute health.gov.au
1: 192.168.1.1 3ms
← router
2:...yul.ebox.ca 12 ms
← ISP
...
8: NYC4. ALTER.NET 24 ms
← here the packet crossed the USA! from NYC- Sacramento!
9: SAC1.ALTER.NET 97 ms
...
16: health.gov.au 253ms
← crossing the US takes time
mtr
like traceroute, but nicer output! try it!
last panel
look up how traceroute works (using TTLs!) it’s simple + cool!
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