38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
---
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tags: [networks, procedural]
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created: Monday, January 13, 2025
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---
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# Ping
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`ping` is perhaps the most basic network debugging tool. It sends
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[ICMP](./ICMP_Protocol.md) echo request packets to a recipient host.
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If the recipient receives the packet and is configured to reply, it sends an
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ICMP echo response packet in return.
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For example:
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```
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$ ping google.com
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PING google.com (142.250.200.14) 56(84) bytes of data.
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64 bytes from lhr48s29-in-f14.1e100.net (142.250.200.14): icmp_seq=1 ttl=116 time=19.1 ms
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64 bytes from lhr48s29-in-f14.1e100.net (142.250.200.14): icmp_seq=2 ttl=116 time=19.2 ms
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64 bytes from lhr48s29-in-f14.1e100.net (142.250.200.14): icmp_seq=3 ttl=116 time=19.1 ms
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64 bytes from lhr48s29-in-f14.1e100.net (142.250.200.14): icmp_seq=4 ttl=116 time=21.1 ms
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```
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The first indicates the IP address of the host you are pinging (once per second,
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by default). The subsequent lines are the response packets, echoed back from
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this host.
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The `icmp_seq` is the number of the request in the sequence. If there was to be
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a gap in the sequence, this would be the clearest indication of a connection
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problem.The packets should not arrive out of order since there is only one
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packet being sent per second.
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`time` is the round-trip time - from the sending of the packet to its return to
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the sender.
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If the packet cannot reach the destination host, the final router to see the
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packet retunes a "host unreachable" packet to `ping`.
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