November 2007
Beginner
642 pages
15h 43m
English
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19.2. Testing Connectivity with ping Problem
Problem
Some services or hosts on your network are not accessible, or have intermittent failures. You don't know if it's a physical problem, a problem with name services, routing, or what the heck. Where do you start?
Solution
Good old ping should always be your first
stop. Use the -c switch to limit
the number of pings; otherwise, it will run until
you stop it with Ctrl-C:
$ ping localhost
PING xena.alrac.net (127.0.1.1) 56(84) bytes of data.
64 bytes from xena.alrac.net (127.0.1.1): icmp_seq=1 ttl=64 time=0.034 ms
64 bytes from xena.alrac.net (127.0.1.1): icmp_seq=2 ttl=64 time=0.037 ms
--- xena.alrac.net ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.034/0.035/0.037/0.006 msPinging localhost first confirms that your network interface is up and operating. You can also ping your hostname and IP address to further confirm that local networking is operating correctly. Then, you can test other hosts:
$ ping -c10 uberpc
PING uberpc.alrac.net (192.168.1.76) 56(84) bytes of data.
64 bytes from uberpc.alrac.net (192.168.1.76): icmp_seq=1 ttl=64 time=5.49 ms
[...]
--- uberpc.alrac.net ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9031ms
rtt min/avg/max/mdev = 0.097/0.108/0.124/0.007 msThe output from that simple command gives you several useful pieces of information, including that name resolution is working and you have a good, clean, fast connection.
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