Manual Pages for UNIX Darwin command on man ping

PING(8) BSD System Manager's Manual PING(8)

NAME

ppiinngg - send ICMP ECHOREQUEST packets to network hosts

SYNOPSIS

ppiinngg [-AAaaDDddffnnooQQqqRRrrvv] [-cc count] [-ii wait] [-ll preload] [-MM mmaasskk | ttiimmee]

[-mm ttl] [-PP policy] [-pp pattern] [-SS srcaddr] [-ss packetsize]

[-tt timeout] [-zz tos] host

ppiinngg [-AAaaDDddffLLnnooQQqqRRrrvv] [-cc count] [-II iface] [-ii wait] [-ll preload]

[-MM mmaasskk | ttiimmee] [-mm ttl] [-PP policy] [-pp pattern] [-SS srcaddr]

[-ss packetsize] [-TT ttl] [-tt timeout] [-zz tos] mcast-group

DESCRIPTION

The ppiinngg utility uses the ICMP protocol's mandatory ECHOREQUEST datagram to elicit an ICMP ECHORESPONSE from a host or gateway. ECHOREQUEST

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. The options are as follows:

-AA Audible. Output a bell (ASCII 0x07) character when no packet is

received before the next packet is transmitted. To cater for

round-trip times that are longer than the interval between trans-

missions, further missing packets cause a bell only if the maxi-

mum number of unreceived packets has increased.

-aa Audible. Include a bell (ASCII 0x07) character in the output

when any packet is received. This option is ignored if other format options are present.

-cc count

Stop after sending (and receiving) count ECHORESPONSE packets.

If this option is not specified, ppiinngg will operate until inter-

rupted.

-DD Set the Don't Fragment bit.

-dd Set the SODEBUG option on the socket being used.

-ff Flood ping. Outputs packets as fast as they come back or one

hundred times per second, whichever is more. For every ECHOREQUEST sent a period ``.'' is printed, while for every ECHOREPLY received a backspace is printed. This provides a rapid display of how many packets are being dropped. Only the

super-user may use this option. This can be very hard on a net-

work and should be used with caution.

-II iface

Source multicast packets with the given interface address. This

flag only applies if the ping destination is a multicast address.

-ii wait

Wait wait seconds between sending each packet. The default is to wait for one second between each packet. The wait time may be

fractional, but only the super-user may specify values less than

1 second. This option is incompatible with the -ff option.

-LL Suppress loopback of multicast packets. This flag only applies

if the ping destination is a multicast address.

-ll preload

If preload is specified, ppiinngg sends that many packets as fast as possible before falling into its normal mode of behavior. Only

the super-user may use this option.

-MM mmaasskk | ttiimmee

Use ICMPMASKREQ or ICMPTSTAMP instead of ICMPECHO. For mmaasskk, print the netmask of the remote machine. Set the net.inet.icmp.maskrepl MIB variable to enable ICMPMASKREPLY.

For ttiimmee, print the origination, reception and transmission time-

stamps.

-mm ttl Set the IP Time To Live for outgoing packets. If not specified,

the kernel uses the value of the net.inet.ip.ttl MIB variable.

-nn Numeric output only. No attempt will be made to lookup symbolic

names for host addresses.

-oo Exit successfully after receiving one reply packet.

-PP policy

policy specifies IPsec policy for the ping session. For details

please refer to ipsec(4) and ipsecsetpolicy(3).

-pp pattern

You may specify up to 16 ``pad'' bytes to fill out the packet you

send. This is useful for diagnosing data-dependent problems in a

network. For example, ``-p ff'' will cause the sent packet to be

filled with all ones.

-QQ Somewhat quiet output. Don't display ICMP error messages that

are in response to our query messages. Originally, the -vv flag

was required to display such errors, but -vv displays all ICMP

error messages. On a busy machine, this output can be overbear-

ing. Without the -QQ flag, ppiinngg prints out any ICMP error mes-

sages caused by its own ECHOREQUEST messages.

-qq Quiet output. Nothing is displayed except the summary lines at

startup time and when finished.

-RR Record route. Includes the RECORDROUTE option in the

ECHOREQUEST packet and displays the route buffer on returned packets. Note that the IP header is only large enough for nine such routes; the traceroute(8) command is usually better at determining the route packets take to a particular destination. If more routes come back than should, such as due to an illegal

spoofed packet, ping will print the route list and then truncate

it at the correct spot. Many hosts ignore or discard the RECORDROUTE option.

-rr Bypass the normal routing tables and send directly to a host on

an attached network. If the host is not on a directly-attached

network, an error is returned. This option can be used to ping a

local host through an interface that has no route through it (e.g., after the interface was dropped by routed(8)).

-SS srcaddr

Use the following IP address as the source address in outgoing packets. On hosts with more than one IP address, this option can be used to force the source address to be something other than the IP address of the interface the probe packet is sent on. If the IP address is not one of this machine's interface addresses, an error is returned and nothing is sent.

-ss packetsize

Specify the number of data bytes to be sent. The default is 56, which translates into 64 ICMP data bytes when combined with the 8 bytes of ICMP header data.

-TT ttl Set the IP Time To Live for multicasted packets. This flag only

applies if the ping destination is a multicast address.

-tt timeout

Specify a timeout, in seconds, before ping exits regardless of

how many packets have been received.

-vv Verbose output. ICMP packets other than ECHORESPONSE that are

received are listed.

-zz tos Use the specified type of service.

When using ppiinngg for fault isolation, it should first be run on the local host, to verify that the local network 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 not included in the packet loss calcula-

tion, although the round trip time of these packets is used in calculat-

ing the round-trip time statistics. When the specified number of packets

have been sent (and received) or if the program is terminated with a SIGINT, a brief summary is displayed, showing the number of packets sent and received, and the minimum, mean, maximum, and standard deviation of

the round-trip times.

If ppiinngg receives a SIGINFO (see the ssttaattuuss argument for stty(1)) signal, the current number of packets sent and received, and the minimum, mean,

and maximum of the round-trip times will be written to the standard error

output.

This program is intended for use in network testing, measurement and man-

agement. Because of the load it can impose on the network, it is unwise to use ppiinngg during normal operations or from automated scripts. IICCMMPP PPAACCKKEETT DDEETTAAIILLSS An IP header without options is 20 bytes. An ICMP ECHOREQUEST packet

contains an additional 8 bytes worth of ICMP header followed by an arbi-

trary amount of data. When a packetsize is given, this indicated the size of this extra piece of data (the default is 56). Thus the amount of data received inside of an IP packet of type ICMP ECHOREPLY will always be 8 bytes more than the requested data space (the ICMP header). If the data space is at least eight bytes large, ppiinngg uses the first eight bytes of this space to include a timestamp which it uses in the computation of round trip times. If less than eight bytes of pad are specified, no round trip times are given. DDUUPPLLIICCAATTEE AANNDD DDAAMMAAGGEEDD PPAACCKKEETTSS The ppiinngg utility will report duplicate and damaged packets. Duplicate

packets should never occur when pinging a unicast address, and seem to be

caused by 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.

Duplicates are expected when pinging a broadcast or multicast address,

since they are not really duplicates but replies from different hosts to the same request. Damaged packets are obviously serious cause for alarm and often indicate broken hardware somewhere in the ppiinngg packet's path (in the network or in the hosts). TTRRYYIINNGG DDIIFFFFEERREENNTT DDAATTAA PPAATTTTEERRNNSS The (inter)network layer should never treat packets differently depending

on the data contained in the data portion. Unfortunately, data-dependent

problems have been known to sneak into networks and remain undetected for long periods of time. In many cases the particular pattern that will have problems is something that does not have sufficient ``transitions'', such as all ones or all zeros, or a pattern right at the edge, such as almost all zeros. It is not necessarily enough to specify a data pattern of all zeros (for example) on the command line because the pattern that is of interest is at the data link level, and the relationship between what 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 cannot be sent across your network or that takes much longer to transfer than other similar length files. You can then examine this file for repeated patterns that you can test using the

-pp option of ppiinngg.

TTTTLL DDEETTAAIILLSS The TTL value of an IP packet represents the maximum number of IP routers that the packet can go through before being thrown away. In current practice you can expect each router in the Internet to decrement the TTL field by exactly one. The TCP/IP specification recommends setting the TTL field for IP packets to 64, but many systems use smaller values (4.3BSD uses 30, 4.2BSD used 15). The maximum possible value of this field is 255, and most UNIX systems set the TTL field of ICMP ECHOREQUEST packets to 255. This is why you

will find you can ``ping'' some hosts, but not reach them with telnet(1)

or ftp(1). In normal operation ppiinngg prints the ttl value from the packet it

receives. When a remote system receives a ping packet, it can do one of

three things with the TTL field in its response:

++oo Not change it; this is what BSD systems did before the 4.3BSD-Tahoe

release. In this case the TTL value in the received packet will be

255 minus the number of routers in the round-trip path.

++oo Set it to 255; this is what current BSD systems do. In this case the TTL value in the received packet will be 255 minus the number of routers in the path from the remote system to the ppiinngging host. ++oo 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.

RETURN VALUES

The ppiinngg utility returns an exit status of zero if at least one response was heard from the specified host; a status of two if the transmission was successful but no responses were received; or another value (from ) if an error occurred.

BUGS

Many Hosts and Gateways ignore the RECORDROUTE option. The maximum IP header length is too small for options like RECORDROUTE to be completely useful. There's not much that can be done about this, however.

Flood pinging is not recommended in general, and flood pinging the broad-

cast address should only be done under very controlled conditions.

The -vv option is not worth much on busy hosts.

BSD October 2, 2002 BSD