Ping: Difference between revisions
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ping is a tool written by the late Mike Muus to measure latency and round-trip time between two hosts connected by a network. Often it is also used to simply debug if the other host is up. It works by sending an [[ICMP]] type 8 packet to the remote host which replies with an [[ICMP]] type 0 packet. Sometimes there is a [[firewall]] preventing a ping from receiving a reply. | ping is a tool written by the late Mike Muus to measure latency and round-trip time between two hosts connected by a network. Often it is also used to simply debug if the other host is up. It works by sending an [[ICMP]] type 8 (request) packet to the remote host which replies with an [[ICMP]] type 0 (reply) packet. Sometimes there is a [[firewall]] preventing a ping from receiving a reply. | ||
This would look like so: | This would look like so: | ||
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If you're using a packet [[sniffer]] you should see both the request and the reply if things are working unmolested. | If you're using a packet [[sniffer]] you should see both the request and the reply if things are working unmolested. | ||
# tcpdump -i [[Variables|rl0]] host gateway.home.lan | |||
18:13:30.601477 IP laptop.home.lan > gateway.home.lan: ICMP echo request, id 36372, seq 2, length 64 | 18:13:30.601477 IP laptop.home.lan > gateway.home.lan: ICMP echo request, id 36372, seq 2, length 64 | ||
18:13:30.601773 IP gateway.home.lan > laptop.home.lan: ICMP echo reply, id 36372, seq 2, length 64 | 18:13:30.601773 IP gateway.home.lan > laptop.home.lan: ICMP echo reply, id 36372, seq 2, length 64 | ||
Latest revision as of 15:22, 16 February 2006
ping is a tool written by the late Mike Muus to measure latency and round-trip time between two hosts connected by a network. Often it is also used to simply debug if the other host is up. It works by sending an ICMP type 8 (request) packet to the remote host which replies with an ICMP type 0 (reply) packet. Sometimes there is a firewall preventing a ping from receiving a reply.
This would look like so:
$ ping -c 1 www.yashy.com PING mail.yashy.com (206.248.137.44): 56 data bytes --- mail.yashy.com ping statistics --- 1 packets transmitted, 0 packets received, 100.0% packet loss
If you're using a packet sniffer you should see both the request and the reply if things are working unmolested.
# tcpdump -i rl0 host gateway.home.lan 18:13:30.601477 IP laptop.home.lan > gateway.home.lan: ICMP echo request, id 36372, seq 2, length 64 18:13:30.601773 IP gateway.home.lan > laptop.home.lan: ICMP echo reply, id 36372, seq 2, length 64
One of the original DoS was a simple ping flood. If you have more bandwidth then your victim, you can do
# ping -f example.com.
and slow your victim to a grinding halt.
A similar tool to ping would be traceroute.
