Ping is a network troubleshooting tool that sends ICMP echo requests that is used for testing connectivity between computers. It, of course, is named after sonar pings that a submarine uses to detect other ships. It is sometimes said to stand for Packet INternet Groper, but this is a backronym.
One difference between the MS-DOS/Windows version of this tool and the Linux version is that, by default, the DOS version quits after 4 pings, the Linux version keeps pinging indefinitely. (Stop it with Ctrl C, or run it with the -c 4 option to stop after 4 pings.)
- Pings Google.
- Note that ping can accept IP addresses or domain names.
Here is how you do a broadcast ping with SUSE, it should work same or similar with every distribution. Log in as root user to perform the following tasks.
- Stop the firewall
- Allow for broadcast pings
echo "0" >/proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
- Verify broadcast pings are allowed
sysctl net.ipv4.icmp_echo_ignore_broadcasts net.ipv4.icmp_echo_ignore_broadcasts = 0
- Find out the broadcast address of the network where you want to broadcast
ifconfig eth1 eth1 Link encap:Ethernet HWaddr 00:1C:F0:BB:06:C8 inet addr:192.168.0.5 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::21c:f0ff:febb:6c8/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:315742 errors:0 dropped:0 overruns:0 frame:0 TX packets:297176 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:195071533 (186.0 Mb) TX bytes:41401952 (39.4 Mb) Interrupt:21 Base address:0x4000
# ping -b 192.168.0.255 WARNING: pinging broadcast address PING 192.168.0.255 (192.168.0.255) 56(84) bytes of data. 64 bytes from 192.168.0.5: icmp_seq=1 ttl=64 time=0.039 ms
If this does not work you can use the following command to search for IP addresses that respond:
for i in $(seq 1 1 5); do (ping -c 1 -w 1 192.168.0.$i >/dev/null && echo $i); done;
Problem: The DNS entry has changed (maybe it is a dynamic one from dyndns), but ping still tries to reach the old ip-address.
Reason: The IP address is cached.
Solution: Restart the name service cache daemon: