ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams (``pings'') have an IP and ICMP header, followed by a struct timeval and then an arbitrary number of ``pad'' bytes used to fill out the packet. ping works with both IPv4 and IPv6.
Allow pinging a broadcast address.
Stop after sending count ECHO_REQUEST packets. With deadline option, ping waits for count ECHO_REPLYpackets, until the timeout expires.
Print timestamp (unix time + microseconds as in gettimeofday) before each line.
IPv6 only. Allocate and set 20 bit flow label (in hex) on echo request packets. If value is zero,kernel allocates random flow label.
Wait interval seconds between sending each packet. The default is to wait for one second between eachpacket normally, or not to wait in flood mode. Only super-user may set interval to values less than 0.2seconds.
interface is either an address, or an interface name. If interface is an address, it sets sourceaddress to specified interface address. If interface in an interface name, it sets source interface tospecified interface. For IPv6, when doing ping to a link-local scope address, link specification (bythe '%'-notation in destination, or by this option) is required.
If preload is specified, ping sends that many packets not waiting for reply. Only the super-user mayselect preload more than 3.
use mark to tag the packets going out. This is useful for variety of reasons within the kernel such asusing policy routing to select specific outbound processing.
Select Path MTU Discovery strategy. pmtudisc_option may be either do (prohibit fragmentation, evenlocal one), want (do PMTU discovery, fragment locally when packet size is large), or dont (do not setDF flag).
IPv6 only. Send ICMPv6 Node Information Queries (RFC4620), instead of Echo Request. CAP_NET_RAW capa‐bility is required.help Show help for NI support.name Queries for Node Names.ipv6 Queries for IPv6 Addresses. There are several IPv6 specific flags.ipv6-globalRequest IPv6 global-scope addresses.ipv6-sitelocalRequest IPv6 site-local addresses.ipv6-linklocalRequest IPv6 link-local addresses.ipv6-allRequest IPv6 addresses on other interfaces.ipv4 Queries for IPv4 Addresses. There is one IPv4 specific flag.ipv4-allRequest IPv4 addresses on other interfaces.subject-ipv6=ipv6addrIPv6 subject address.subject-ipv4=ipv4addrIPv4 subject address.subject-name=nodenameSubject name. If it contains more than one dot, fully-qualified domain name is assumed.subject-fqdn=nodenameSubject name. Fully-qualified domain name is always assumed.
Numeric output only. No attempt will be made to lookup symbolic names for host addresses.
You may specify up to 16 ``pad'' bytes to fill out the packet you send. This is useful for diagnosingdata-dependent problems in a network. For example, -p ff will cause the sent packet to be filled withall ones.
Quiet output. Nothing is displayed except the summary lines at startup time and when finished.
Specifies the number of data bytes to be sent. The default is 56, which translates into 64 ICMP databytes when combined with the 8 bytes of ICMP header data.
Set socket sndbuf. If not specified, it is selected to buffer not more than one packet.
ttl ping only. Set the IP Time to Live.
Set special IP timestamp options. timestamp option may be either tsonly (only timestamps), tsandaddr(timestamps and addresses) or tsprespec host1 [host2 [host3 [host4]]] (timestamp prespecified hops).
Specify a timeout, in seconds, before ping exits regardless of how many packets have been sent orreceived. In this case ping does not stop after count packet are sent, it waits either for deadlineexpire or until count probes are answered or for some error notification from network.
Time to wait for a response, in seconds. The option affects only timeout in absence of any responses,otherwise ping waits for two RTTs.When using ping for fault isolation, it should first be run on the local host, to verify that the local net‐work interface is up and running. Then, hosts and gateways further and further away should be ``pinged''.Round-trip times and packet loss statistics are computed. If duplicate packets are received, they are notincluded in the packet loss calculation, although the round trip time of these packets is used in calculatingthe minimum/average/maximum round-trip time numbers. When the specified number of packets have been sent (andreceived) or if the program is terminated with a SIGINT, a brief summary is displayed. Shorter current statis‐tics can be obtained without termination of process with signal SIGQUIT.If ping does not receive any reply packets at all it will exit with code 1. If a packet count and deadline areboth specified, and fewer than count packets are received by the time the deadline has arrived, it will alsoexit with code 1. On other error it exits with code 2. Otherwise it exits with code 0. This makes it possibleto use the exit code to see if a host is alive or not.This program is intended for use in network testing, measurement and management. Because of the load it canimpose on the network, it is unwise to use ping during normal operations or from automated scripts.ICMP PACKET DETAILSAn IP header without options is 20 bytes. An ICMP ECHO_REQUEST packet contains an additional 8 bytes worth ofICMP header followed by an arbitrary amount of data. When a packetsize is given, this indicated the size ofthis extra piece of data (the default is 56). Thus the amount of data received inside of an IP packet of typeICMP ECHO_REPLY will always be 8 bytes more than the requested data space (the ICMP header).If the data space is at least of size of struct timeval ping uses the beginning bytes of this space to includea timestamp which it uses in the computation of round trip times. If the data space is shorter, no round triptimes are given.DUPLICATE AND DAMAGED PACKETSping will report duplicate and damaged packets. Duplicate packets should never occur, and seem to be causedby inappropriate link-level retransmissions. Duplicates may occur in many situations and are rarely (if ever)a good sign, although the presence of low levels of duplicates may not always be cause for alarm.Damaged packets are obviously serious cause for alarm and often indicate broken hardware somewhere in the pingpacket's path (in the network or in the hosts).TRYING DIFFERENT DATA PATTERNSThe (inter)network layer should never treat packets differently depending on the data contained in the dataportion. Unfortunately, data-dependent problems have been known to sneak into networks and remain undetectedfor long periods of time. In many cases the particular pattern that will have problems is something thatdoesn't have sufficient ``transitions'', such as all ones or all zeros, or a pattern right at the edge, suchas almost all zeros. It isn't necessarily enough to specify a data pattern of all zeros (for example) on thecommand line because the pattern that is of interest is at the data link level, and the relationship betweenwhat you type and what the controllers transmit can be complicated.This means that if you have a data-dependent problem you will probably have to do a lot of testing to find it.If you are lucky, you may manage to find a file that either can't be sent across your network or that takesmuch longer to transfer than other similar length files. You can then examine this file for repeated patternsthat you can test using the -p option of ping.TTL DETAILSThe TTL value of an IP packet represents the maximum number of IP routers that the packet can go throughbefore being thrown away. In current practice you can expect each router in the Internet to decrement the TTLfield by exactly one.The TCP/IP specification states that the TTL field for TCP packets should be set to 60, but many systems usesmaller values (4.3 BSD uses 30, 4.2 used 15).The maximum possible value of this field is 255, and most Unix systems set the TTL field of ICMP ECHO_REQUESTpackets to 255. This is why you will find you can ``ping'' some hosts, but not reach them with telnet(1) orftp(1).In normal operation ping prints the TTL value from the packet it receives. When a remote system receives aping packet, it can do one of three things with the TTL field in its response:· Not change it; this is what Berkeley Unix systems did before the 4.3BSD Tahoe release. In this case the TTLvalue in the received packet will be 255 minus the number of routers in the round-trip path.· Set it to 255; this is what current Berkeley Unix systems do. In this case the TTL value in the receivedpacket will be 255 minus the number of routers in the path from the remote system to the pinging host.· Set it to some other value. Some machines use the same value for ICMP packets that they use for TCP packets,for example either 30 or 60. Others may use completely wild values.BUGS· Many Hosts and Gateways ignore the RECORD_ROUTE option.· The maximum IP header length is too small for options like RECORD_ROUTE to be completely useful. There'snot much that can be done about this, however.· Flood pinging is not recommended in general, and flood pinging the broadcast address should only be doneunder very controlled conditions.