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Guide: ping

Ping is perhaps the simplest of the tools recommended for use in SCC365. This tools uses ICMP Echo Request/Reply packets to determine connectivity between 2 point in a network that should support ICMP (such as hosts and routers).

Ping can be used with the command "ping" followed by any flags.

  • -c: The number of echo requests to make before automatically exiting
  • -i: The time to wait between each request (in seconds)

📖 There is more ping can do, see the ping man page for more!

Example: Making Requests

  • To run a ping to a given host, simply run the command and specify the host afterwards: 
    ping lancaster.ac.uk
    This will continue to run until exited (typically Ctrl-C)
  • To run the same action but limited to 5 requests, the -c flag can be used: 
    ping -c 5 lancaster.ac.uk
    Now after the fifth request that program will automatically be terminated. This is particularly useful when automating tests though scripts.
  • To run the same action as above but make each request be sent after each 0.5s rather than 1s: 
    ping -c 5 -i 0.5 lancaster.ac.uk

💡 Tip: In the Mininet prompt, a ping can easily be sent between hosts using host command prefixing and auto name-to-IP tools. For example, the following command in the Mininet prompt would ping between h1 and h9: mininet> h1 ping -c 3 -i 0.75 h9

Example: Parsing Results

The output from ping, if targeting a reachable host, should look something like:

PING lancaster.ac.uk (148.88.65.80): 56 data bytes
64 bytes from 148.88.65.80: icmp_seq=0 ttl=49 time=45.561 ms
64 bytes from 148.88.65.80: icmp_seq=1 ttl=49 time=52.544 ms
64 bytes from 148.88.65.80: icmp_seq=2 ttl=49 time=83.972 ms
64 bytes from 148.88.65.80: icmp_seq=3 ttl=49 time=46.751 ms
64 bytes from 148.88.65.80: icmp_seq=4 ttl=49 time=46.945 ms

--- lancaster.ac.uk ping statistics ---
5 packets transmitted, 5 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 45.561/55.155/83.972/14.610 ms
  • There should be a line produced for each request (provided it is not being suppressed) that contains stats for that single request: 
    64 bytes from 148.88.65.80: icmp_seq=0 ttl=49 time=45.561 ms
    For example, this shows that:
    • 64bytes were received from the resolved IP for lancaster.ac.uk (148.88.65.80)
    • The packet's TLL was decremented to 49 from its default
    • The round trip time for the ping was 45.561ms
  • The stats at the end are summarizing all requests (including failed requests if any): 
    5 packets transmitted, 5 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 45.561/55.155/83.972/14.610 ms
    This tells us that:
    • As 5 packets were sent and 5 received, no packets were lost
    • The average RTT was 55.155ms (and other RTT info)