1PING(8) System Manager's Manual: iputils PING(8)
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6 ping - send ICMP ECHO_REQUEST to network hosts
7
9 ping [-aAbBdDfhLnOqrRUvV46] [-c count] [-F flowlabel] [-i interval] [-I
10 interface] [-l preload] [-m mark] [-M pmtudisc_option] [-N node‐
11 info_option] [-w deadline] [-W timeout] [-p pattern] [-Q tos] [-s pack‐
12 etsize] [-S sndbuf] [-t ttl] [-T timestamp option] [hop ...] destina‐
13 tion
14
17 ping uses the ICMP protocol's mandatory ECHO_REQUEST datagram to elicit
18 an ICMP ECHO_RESPONSE from a host or gateway. ECHO_REQUEST datagrams
19 (``pings'') have an IP and ICMP header, followed by a struct timeval
20 and then an arbitrary number of ``pad'' bytes used to fill out the
21 packet.
22 ping works with both IPv4 and IPv6. Using only one of them explicitly
24 can be enforced by specifying -4 or -6.
25 ping can also send IPv6 Node Information Queries (RFC4620). Intermedi‐
27 ate hops may not be allowed, because IPv6 source routing was deprecated
28 (RFC5095).
29
31 -4 Use IPv4 only.
32 -6 Use IPv6 only.
34 -a Audible ping.
36 -A Adaptive ping. Interpacket interval adapts to round-trip time,
38 so that effectively not more than one (or more, if preload is
39 set) unanswered probe is present in the network. Minimal inter‐
40 val is 200msec for not super-user. On networks with low rtt
41 this mode is essentially equivalent to flood mode.
42 -b Allow pinging a broadcast address.
44 -B Do not allow ping to change source address of probes. The
46 address is bound to one selected when ping starts.
47 -c count
49 Stop after sending count ECHO_REQUEST packets. With deadline
50 option, ping waits for count ECHO_REPLY packets, until the time‐
51 out expires.
52 -d Set the SO_DEBUG option on the socket being used. Essentially,
54 this socket option is not used by Linux kernel.
55 -D Print timestamp (unix time + microseconds as in gettimeofday)
57 before each line.
58 -f Flood ping. For every ECHO_REQUEST sent a period ``.'' is
60 printed, while for ever ECHO_REPLY received a backspace is
61 printed. This provides a rapid display of how many packets are
62 being dropped. If interval is not given, it sets interval to
63 zero and outputs packets as fast as they come back or one hun‐
64 dred times per second, whichever is more. Only the super-user
65 may use this option with zero interval.
66 -F flow label
68 IPv6 only. Allocate and set 20 bit flow label (in hex) on echo
69 request packets. If value is zero, kernel allocates random flow
70 label.
71 -h Show help.
73 -i interval
75 Wait interval seconds between sending each packet. The default
76 is to wait for one second between each packet normally, or not
77 to wait in flood mode. Only super-user may set interval to val‐
78 ues less 0.2 seconds.
79 -I interface
81 interface is either an address, or an interface name. If inter‐
82 face is an address, it sets source address to specified inter‐
83 face address. If interface in an interface name, it sets source
84 interface to specified interface. For IPv6, when doing ping to
85 a link-local scope address, link specification (by the '%'-nota‐
86 tion in destination, or by this option) is required.
87 -l preload
89 If preload is specified, ping sends that many packets not wait‐
90 ing for reply. Only the super-user may select preload more than
91 3.
92 -L Suppress loopback of multicast packets. This flag only applies
94 if the ping destination is a multicast address.
95 -m mark
97 use mark to tag the packets going out. This is useful for vari‐
98 ety of reasons within the kernel such as using policy routing to
99 select specific outbound processing.
100 -M pmtudisc_opt
102 Select Path MTU Discovery strategy. pmtudisc_option may be
103 either do (prohibit fragmentation, even local one), want (do
104 PMTU discovery, fragment locally when packet size is large), or
105 dont (do not set DF flag).
106 -N nodeinfo_option
108 IPv6 only. Send ICMPv6 Node Information Queries (RFC4620),
109 instead of Echo Request. CAP_NET_RAW capability is required.
110 help Show help for NI support.
112 name Queries for Node Names.
114 ipv6 Queries for IPv6 Addresses. There are several IPv6 spe‐
116 cific flags.
117 ipv6-global
119 Request IPv6 global-scope addresses.
120 ipv6-sitelocal
122 Request IPv6 site-local addresses.
123 ipv6-linklocal
125 Request IPv6 link-local addresses.
126 ipv6-all
128 Request IPv6 addresses on other interfaces.
129 ipv4 Queries for IPv4 Addresses. There is one IPv4 specific
131 flag.
132 ipv4-all
134 Request IPv4 addresses on other interfaces.
135 subject-ipv6=ipv6addr
137 IPv6 subject address.
138 subject-ipv4=ipv4addr
140 IPv4 subject address.
141 subject-name=nodename
143 Subject name. If it contains more than one dot, fully-
144 qualified domain name is assumed.
145 subject-fqdn=nodename
147 Subject name. Fully-qualified domain name is always
148 assumed.
149 -n Numeric output only. No attempt will be made to lookup symbolic
151 names for host addresses.
152 -O Report outstanding ICMP ECHO reply before sending next packet.
154 This is useful together with the timestamp -D to log output to a
155 diagnostic file and search for missing answers.
156 -p pattern
158 You may specify up to 16 ``pad'' bytes to fill out the packet
159 you send. This is useful for diagnosing data-dependent problems
160 in a network. For example, -p ff will cause the sent packet to
161 be filled with all ones.
162 -q Quiet output. Nothing is displayed except the summary lines at
164 startup time and when finished.
165 -Q tos Set Quality of Service -related bits in ICMP datagrams. tos can
167 be decimal (ping only) or hex number.
168 In RFC2474, these fields are interpreted as 8-bit Differentiated
170 Services (DS), consisting of: bits 0-1 (2 lowest bits) of sepa‐
171 rate data, and bits 2-7 (highest 6 bits) of Differentiated Ser‐
172 vices Codepoint (DSCP). In RFC2481 and RFC3168, bits 0-1 are
173 used for ECN.
174 Historically (RFC1349, obsoleted by RFC2474), these were inter‐
176 preted as: bit 0 (lowest bit) for reserved (currently being
177 redefined as congestion control), 1-4 for Type of Service and
178 bits 5-7 (highest bits) for Precedence.
179 -r Bypass the normal routing tables and send directly to a host on
181 an attached interface. If the host is not on a directly-
182 attached network, an error is returned. This option can be used
183 to ping a local host through an interface that has no route
184 through it provided the option -I is also used.
185 -R ping only. Record route. Includes the RECORD_ROUTE option in
187 the ECHO_REQUEST packet and displays the route buffer on
188 returned packets. Note that the IP header is only large enough
189 for nine such routes. Many hosts ignore or discard this option.
190 -s packetsize
192 Specifies the number of data bytes to be sent. The default is
193 56, which translates into 64 ICMP data bytes when combined with
194 the 8 bytes of ICMP header data.
195 -S sndbuf
197 Set socket sndbuf. If not specified, it is selected to buffer
198 not more than one packet.
199 -t ttl ping only. Set the IP Time to Live.
201 -T timestamp option
203 Set special IP timestamp options. timestamp option may be
204 either tsonly (only timestamps), tsandaddr (timestamps and
205 addresses) or tsprespec host1 [host2 [host3 [host4]]] (timestamp
206 prespecified hops).
207 -U Print full user-to-user latency (the old behaviour). Normally
209 ping prints network round trip time, which can be different f.e.
210 due to DNS failures.
211 -v Verbose output.
213 -V Show version and exit.
215 -w deadline
217 Specify a timeout, in seconds, before ping exits regardless of
218 how many packets have been sent or received. In this case ping
219 does not stop after count packet are sent, it waits either for
220 deadline expire or until count probes are answered or for some
221 error notification from network.
222 -W timeout
224 Time to wait for a response, in seconds. The option affects only
225 timeout in absence of any responses, otherwise ping waits for
226 two RTTs.
227 When using ping for fault isolation, it should first be run on the
229 local host, to verify that the local network interface is up and run‐
230 ning. Then, hosts and gateways further and further away should be
231 ``pinged''. Round-trip times and packet loss statistics are computed.
232 If duplicate packets are received, they are not included in the packet
233 loss calculation, although the round trip time of these packets is used
234 in calculating the minimum/average/maximum round-trip time numbers.
235 When the specified number of packets have been sent (and received) or
236 if the program is terminated with a SIGINT, a brief summary is dis‐
237 played. Shorter current statistics can be obtained without termination
238 of process with signal SIGQUIT.
239 If ping does not receive any reply packets at all it will exit with
241 code 1. If a packet count and deadline are both specified, and fewer
242 than count packets are received by the time the deadline has arrived,
243 it will also exit with code 1. On other error it exits with code 2.
244 Otherwise it exits with code 0. This makes it possible to use the exit
245 code to see if a host is alive or not.
246 This program is intended for use in network testing, measurement and
248 management. Because of the load it can impose on the network, it is
249 unwise to use ping during normal operations or from automated scripts.
250
252 An IP header without options is 20 bytes. An ICMP ECHO_REQUEST packet
253 contains an additional 8 bytes worth of ICMP header followed by an
254 arbitrary amount of data. When a packetsize is given, this indicated
255 the size of this extra piece of data (the default is 56). Thus the
256 amount of data received inside of an IP packet of type ICMP ECHO_REPLY
257 will always be 8 bytes more than the requested data space (the ICMP
258 header).
259 If the data space is at least of size of struct timeval ping uses the
261 beginning bytes of this space to include a timestamp which it uses in
262 the computation of round trip times. If the data space is shorter, no
263 round trip times are given.
264
266 ping will report duplicate and damaged packets. Duplicate packets
267 should never occur, and seem to be caused by inappropriate link-level
268 retransmissions. Duplicates may occur in many situations and are
269 rarely (if ever) a good sign, although the presence of low levels of
270 duplicates may not always be cause for alarm.
271 Damaged packets are obviously serious cause for alarm and often indi‐
273 cate broken hardware somewhere in the ping packet's path (in the net‐
274 work or in the hosts).
275
277 The (inter)network layer should never treat packets differently depend‐
278 ing on the data contained in the data portion. Unfortunately, data-
279 dependent problems have been known to sneak into networks and remain
280 undetected for long periods of time. In many cases the particular pat‐
281 tern that will have problems is something that doesn't have sufficient
282 ``transitions'', such as all ones or all zeros, or a pattern right at
283 the edge, such as almost all zeros. It isn't necessarily enough to
284 specify a data pattern of all zeros (for example) on the command line
285 because the pattern that is of interest is at the data link level, and
286 the relationship between what you type and what the controllers trans‐
287 mit can be complicated.
288 This means that if you have a data-dependent problem you will probably
290 have to do a lot of testing to find it. If you are lucky, you may man‐
291 age to find a file that either can't be sent across your network or
292 that takes much longer to transfer than other similar length files.
293 You can then examine this file for repeated patterns that you can test
294 using the -p option of ping.
295
297 The TTL value of an IP packet represents the maximum number of IP
298 routers that the packet can go through before being thrown away. In
299 current practice you can expect each router in the Internet to decre‐
300 ment the TTL field by exactly one.
301 The TCP/IP specification states that the TTL field for TCP packets
303 should be set to 60, but many systems use smaller values (4.3 BSD uses
304 30, 4.2 used 15).
305 The maximum possible value of this field is 255, and most Unix systems
307 set the TTL field of ICMP ECHO_REQUEST packets to 255. This is why you
308 will find you can ``ping'' some hosts, but not reach them with tel‐
309 net(1) or ftp(1).
310 In normal operation ping prints the TTL value from the packet it
312 receives. When a remote system receives a ping packet, it can do one
313 of three things with the TTL field in its response:
314 · Not change it; this is what Berkeley Unix systems did before the
316 4.3BSD Tahoe release. In this case the TTL value in the received
317 packet will be 255 minus the number of routers in the round-trip
318 path.
319 · Set it to 255; this is what current Berkeley Unix systems do. In
321 this case the TTL value in the received packet will be 255 minus the
322 number of routers in the path from the remote system to the pinging
323 host.
324 · Set it to some other value. Some machines use the same value for ICMP
326 packets that they use for TCP packets, for example either 30 or 60.
327 Others may use completely wild values.
328
330 · Many Hosts and Gateways ignore the RECORD_ROUTE option.
331 · The maximum IP header length is too small for options like
333 RECORD_ROUTE to be completely useful. There's not much that can be
334 done about this, however.
335 · Flood pinging is not recommended in general, and flood pinging the
337 broadcast address should only be done under very controlled condi‐
338 tions.
339
341 netstat(1), ifconfig(8).
342
344 The ping command appeared in 4.3BSD.
345 The version described here is its descendant specific to Linux.
347 As of version s20150815, the ping6 binary doesn't exist anymore. It
349 has been merged into ping. Creating a symlink named ping6 pointing to
350 ping will result in the same funcionality as before.
351
353 ping requires CAP_NET_RAW capability to be executed 1) if the program
354 is used for non-echo queries (See -N option), or 2) if kernel does not
355 support non-raw ICMP sockets, or 3) if the user is not allowed to cre‐
356 ate an ICMP echo socket. The program may be used as set-uid root.
357
359 ping is part of iputils package and the latest versions are available
360 in source form at http://www.skbuff.net/iputils/iputils-cur‐
361 rent.tar.bz2.
362iputils-160308 PING(8)