ping
6 send ICMP ECHO_REQUEST to network hosts
see also :
ping6 - netstat - ifconfig
Synopsis
ping
[-LRUbdfnqrvVaAB] [-c count] [-m
mark] [-i interval] [-l
preload] [-p pattern] [-s
packetsize] [-t ttl] [-w
deadline] [-F flowlabel] [-I
interface] [-M hint] [-N
nioption] [-Q tos] [-S
sndbuf] [-T timestamp option]
[-W timeout] [hop ...]
destination
add an example, a script, a trick and tips
examples
source
Ping two ethernet card on the same computer and on the same subnet
To fix this issue, i use two virtual machine. And i can ping eth1
or eth2, with eth2 or eth1.
Thank you,all for yours comments and help.
source
LINUX Ping host, Display error on failure
I think awk is not necessary. Unless I'm missing
something that code should do the trick:
#!/bin/bash
host=$1
ping -c1 $host > /dev/null 2> /dev/null
[[ $? == 0 ]] && echo "$host is up" || echo "$host is down/not reachable"
Here an example:
$ ./checkping www.google.com
www.google.com is up
$ ./checkping www.google.utld
www.google.utld is down/not reachable
source
How can I ping via an alternate gateway?
Sorry, you can only have one default gateway.
You can have multiple gateways, but only one for every network.
The problem is, that both mentioned IPs are in the same network.
Also you specified your CIDRs wrongly: You meant 10.1.1.0/24 as
having a subnet of 255.255.255.0; or even have a bigger subnet
e.g. 10.0.0.0/8 as being 255.0.0.0.
You can therefore ping any host inside your network (10.0.0.0/8)
or any host reachable via a (or the) gateway. But having two
gateways for the same network is not possible.
source
Linux Ping: Show time out
I am afraid but there is no 100% solution to that with standard
ping. Even with ping -v for verbose output ping would be
silent in case of timeouts. You could try to use:
ping -w 2 192.168.199.1
PING 192.168.199.1 (192.168.199.1) 56(84) bytes of data.
--- 192.168.199.1 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1007ms
This would stop ping after 2 seconds and then show the number of
packets transmitted and packet loss. Another option would be to
use mtr.
source
How to ping when behind a proxy?
In general you can't. ping needs a direct network
connection on the IP level to do its work. A proxy works on a
higher layer of the TCP/IP network model,
where there is no direct access to the IP protocol.
You would need to somehow circumvent the proxy (change firewall
settings, use a VPN, ...). Whether this is possible (and allowed)
depends on your network configuration, but it's probably not
possible.
As a workaround, there are many web-based ping services available
(search for "web-based ping"). These will work.
source
linux ping not actually sending 1 packet per second
It looks like you have one of the versions of ping
that does a DNS lookup for every received packet. Since a DNS UDP
packet has to traverse the same congested network as ping
packets, the packet may be dropped. With timeouts and retries it
can take significant time for a DNS request to return data. The
time consumed waiting for a DNS response delays the sending of
the next ping packet because your ping is both
single-threaded and doesn't use an asynchronous timer to drive
each ping.
If my diagnosis is correct, adding -n to
ping should get rid of the delays.
source
(linux) tool to monitor "quality" of tcp connection?
How do you define "how fast the packets get delivered" ? If you
want to know how much time it takes for a packet to reach point B
from point A, then I think it can't be done without
sub-millisecond accurate clock synchronization.
What I would try is to capture some real traffic (ie. while
actually using your application), and analyze it with WireShark,
looking for the delay between some data sent and the
corresponding ACK packet. That gives you the round trip time
(RTT) for your traffic.
update:
The TCP stack has to keep track of the RTT for each connection.
(it's used to optimize packet transmission and manage window
size). If you're using Linux, and it's your own application, you
can use the getsockopt(fd,.. ,TCP_INFO,...) the data
returned includes all this internal parameters. You could peek at
this data every second and pipe to a display app.
source
How do I check that a *nix machine is online without ping?
nc -z $REMOTESERVER 22
echo $?
If you are using SSH to do rsync that port should be open.
source
Test script if host is back online
The idea looks right to me. By using while :; do ...
you can make it portable to normal Bourne shells. The
expr calls seems unnecessary. Also, you probably
want to break out of the loop when the host is found.
while :; do
if ping -c 1 $1; then
notify-send "$1 back online"
break
fi
sleep 30s
done
description
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.
ping6
can also send Node Information Queries (RFC4620).
options
-a
Audible ping.
-A
Adaptive ping. Interpacket interval adapts to round-trip
time, so that effectively not more than one (or more, if
preload is set) unanswered probes present in the network.
Minimal interval is 200msec for not super-user. On networks
with low rtt this mode is essentially equivalent to flood
mode.
-b
Allow pinging a broadcast address.
-B
Do not allow ping to change source address of
probes. The address is bound to one selected when
ping starts.
-m mark
use mark to tag the
packets going out. This is useful for variety of reasons
within the kernel such as using policy routing to select
specific outbound processing.
-c count
Stop after sending count
ECHO_REQUEST packets. With deadline option,
ping waits for count ECHO_REPLY packets, until
the timeout expires.
-d
Set the SO_DEBUG option on the socket being used.
Essentially, this socket option is not used by Linux
kernel.
-F flow label
Allocate and set 20 bit flow
label on echo request packets. (Only ping6). If value
is zero, kernel allocates random flow label.
-f
Flood ping. For every ECHO_REQUEST sent a period
’’.’’ is printed, while for ever
ECHO_REPLY received a backspace is printed. This provides a
rapid display of how many packets are being dropped. If
interval is not given, it sets interval to zero and outputs
packets as fast as they come back or one hundred times per
second, whichever is more. Only the super-user may use this
option with zero interval.
-i interval
Wait interval seconds
between sending each packet. The default is to wait for one
second between each packet normally, or not to wait in flood
mode. Only super-user may set interval to values less 0.2
seconds.
-I interface
address
Set source address to specified
interface address. Argument may be numeric IP address or
name of device. When pinging IPv6 link-local address this
option is required.
-l preload
If preload is specified,
ping sends that many packets not waiting for reply.
Only the super-user may select preload more than 3.
-L
Suppress loopback of multicast packets. This flag only
applies if the ping destination is a multicast address.
-N nioption
Send ICMPv6 Node Information
Queries (RFC4620), instead of Echo Request.
name
Queries for Node Names.
ipv6
Queries for IPv6 Addresses. There are several IPv6
specific flags.
ipv6-global
Request IPv6 global-scope
addresses.
ipv6-sitelocal
Request IPv6 site-local
addresses.
ipv6-linklocal
Request IPv6 link-local
addresses.
ipv6-all
Request IPv6 addresses on other
interfaces.
ipv4
Queries for IPv4 Addresses. There is one IPv4 specific
flag.
ipv4-all
Request IPv4 addresses on other
interfaces.
subject-ipv6=ipv6addr
IPv6 subject address.
subject-ipv4=ipv4addr
IPv4 subject address.
subject-name=nodename
Subject name. If it contains
more than one dot, fully-qualified domain name is
assumed.
subject-fqdn=nodename
Subject name. Fully-qualified
domain name is always assumed.
-n
Numeric output only. No attempt will be made to lookup
symbolic names for host addresses.
-p 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.
-D
Print timestamp (unix time + microseconds as in
gettimeofday) before each line.
-Q tos
Set Quality of Service -related bits in ICMP datagrams.
tos can be either decimal or hex number.
Traditionally (RFC1349), these have been interpreted as: 0
for reserved (currently being redefined as congestion
control), 1-4 for Type of Service and 5-7 for Precedence.
Possible settings for Type of Service are: minimal cost:
0x02, reliability: 0x04, throughput: 0x08, low delay: 0x10.
Multiple TOS bits should not be set simultaneously. Possible
settings for special Precedence range from priority (0x20)
to net control (0xe0). You must be root (CAP_NET_ADMIN
capability) to use Critical or higher precedence value. You
cannot set bit 0x01 (reserved) unless ECN has been enabled
in the kernel. In RFC2474, these fields has been redefined
as 8-bit Differentiated Services (DS), consisting of: bits
0-1 of separate data (ECN will be used, here), and bits 2-7
of Differentiated Services Codepoint (DSCP).
-q
Quiet output. Nothing is displayed except the summary
lines at startup time and when finished.
-R
Record route. Includes the RECORD_ROUTE option in the
ECHO_REQUEST packet and displays the route buffer on
returned packets. Note that the IP header is only large
enough for nine such routes. Many hosts ignore or discard
this option.
-r
Bypass the normal routing tables and send directly to a
host on an attached interface. 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 provided the option -I is
also used.
-s packetsize
Specifies 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.
-S sndbuf
Set socket sndbuf. If not
specified, it is selected to buffer not more than one
packet.
-t ttl
Set the IP Time to Live.
-T timestamp
option
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).
-M hint
Select Path MTU Discovery
strategy. hint may be either do (prohibit
fragmentation, even local one), want (do PMTU
discovery, fragment locally when packet size is large), or
dont (do not set DF flag).
-U
Print full user-to-user latency (the old behaviour).
Normally ping prints network round trip time, which
can be different f.e. due to DNS failures.
-v
Verbose output.
-V
Show version and exit.
-w deadline
Specify a timeout, in seconds,
before ping exits regardless of how many packets have
been sent or received. In this case ping does not
stop after count packet are sent, it waits either for
deadline expire or until count probes are
answered or for some error notification from network.
-W timeout
Time to wait for a response, in
seconds. The option affects only timeout in absense 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 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 calculation, although the round trip time of
these packets is used in calculating the
minimum/average/maximum round-trip time numbers. 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. Shorter current statistics 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 are
both specified, and fewer than count packets are
received by the time the deadline has arrived, it
will also exit with code 1. On other error it exits with
code 2. Otherwise it exits with code 0. This makes it
possible to 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 can impose on the
network, it is unwise to use ping during normal
operations or from automated scripts.
availability
ping is part of iputils package and the latest
versions are available in source form at
http://www.skbuff.net/iputils/iputils-current.tar.bz2.
duplicate and damaged packets
ping will report duplicate and damaged packets. Duplicate
packets should never occur, 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.
Damaged packets are obviously serious cause for alarm and often
indicate broken hardware somewhere in the ping packet’s
path (in the network or in the hosts).
icmp packet details
An IP header without options is 20 bytes. An ICMP ECHO_REQUEST
packet contains an additional 8 bytes worth of ICMP header
followed by an arbitrary 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 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 include a
timestamp which it uses in the computation of round trip times.
If the data space is shorter, no round trip times are given.
security
ping requires CAP_NET_RAWIO capability to be executed. It
may be used as set-uid root.
trying different data patterns
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 doesn’t have sufficient ’’transitions’’, such as
all ones or all zeros, or a pattern right at the edge, such as
almost all zeros. It isn’t 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 can’t 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 -p option of
ping.
ttl details
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 states that the TTL field for TCP
packets should be set to 60, but many systems use smaller 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_REQUEST 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 ping 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:
•
Not change it; this is what Berkeley Unix 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.
•
Set it to 255; this is what current Berkeley Unix 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 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’s not
much that that can be done about this, however.
•
Flood pinging is not recommended in general, and flood
pinging the broadcast address should only be done under very
controlled conditions.
history
The ping
command appeared in 4.3BSD.
The version
described here is its descendant specific to Linux.
see also
netstat ,
ifconfig .