diff options
-rw-r--r-- | sbin/ping/ping.8 | 139 |
1 files changed, 79 insertions, 60 deletions
diff --git a/sbin/ping/ping.8 b/sbin/ping/ping.8 index 8478cb9..6539352 100644 --- a/sbin/ping/ping.8 +++ b/sbin/ping/ping.8 @@ -30,7 +30,7 @@ .\" SUCH DAMAGE. .\" .\" @(#)ping.8 8.2 (Berkeley) 12/11/93 -.\" $Id: ping.8,v 1.9 1997/03/02 06:32:42 imp Exp $ +.\" $Id: ping.8,v 1.10 1997/03/02 20:01:07 imp Exp $ .\" .Dd March 1, 1997 .Dt PING 8 @@ -41,45 +41,48 @@ .Tn ICMP ECHO_REQUEST packets to network hosts .Sh SYNOPSIS -.Nm ping +.Nm .Op Fl QRadfnqrv .Op Fl c Ar count .Op Fl i Ar wait .Op Fl l Ar preload .Op Fl p Ar pattern .Op Fl s Ar packetsize -[ -.Ar host -| +.Bo +.Ar host | .Op Fl L .Op Fl I Ar interface .Op Fl T Ar ttl .Ar mcast-group -] +.Bc .Sh DESCRIPTION .Nm Ping uses the .Tn ICMP -protocol's mandatory +.No protocol Ap s mandatory .Tn ECHO_REQUEST datagram to elicit an .Tn ICMP ECHO_RESPONSE from a host or gateway. .Tn ECHO_REQUEST -datagrams (``pings'') have an IP and +datagrams +.Pq Dq pings +have an IP and .Tn ICMP -header, -followed by a +header, followed by a .Dq struct timeval -and then an arbitrary number of ``pad'' bytes used to fill out the -packet. -The options are as follows: +and then an arbitrary number of +.Dq pad +bytes used to fill out the packet. The options are as follows: .Bl -tag -width Ds .It Fl a -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. +Audible. Include a bell +.Pq ASCII 0x07 +character in the output when any packet is received. This option is ignored +if other format options are present. .It Fl c Ar count -Stop after sending (and receiving) +Stop after sending +.Pq and receiving .Ar count .Tn ECHO_RESPONSE packets. @@ -93,7 +96,9 @@ Outputs packets as fast as they come back or one hundred times per second, whichever is more. For every .Tn ECHO_REQUEST -sent a period ``.'' is printed, while for every +sent a period +.Dq \&. +is printed, while for every .Tn ECHO_REPLY received a backspace is printed. This provides a rapid display of how many packets are being dropped. @@ -128,7 +133,9 @@ This flag only applies if the ping destination is a multicast address. Numeric output only. No attempt will be made to lookup symbolic names for host addresses. .It Fl p Ar pattern -You may specify up to 16 ``pad'' bytes to fill out the packet you send. +You may specify up to 16 +.Dq pad +bytes to fill out the packet you send. This is useful for diagnosing data-dependent problems in a network. For example, .Dq Li \-p ff @@ -136,7 +143,8 @@ will cause the sent packet to be filled with all ones. .It Fl Q Somewhat quiet output. -Don't display ICMP error messages that are in response to our query messages. +.No Don Ap t +display ICMP error messages that are in response to our query messages. Originally, the .Fl v flag was required to display such errors, but @@ -173,8 +181,11 @@ 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 -.Xr routed 8 ) . +that has no route through it +.Po +e.g., after the interface was dropped by +.Xr routed 8 +.Pc . .It Fl s Ar packetsize Specifies the number of data bytes to be sent. The default is 56, which translates into 64 @@ -195,47 +206,46 @@ that are received are listed. .El .Pp When using -.Nm ping +.Nm 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''. +Then, hosts and gateways further and further away should be +.Dq 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 +When the specified number of packets have been sent +.Pq and received +or if the program is terminated with a .Dv SIGINT , a brief summary is displayed. .Pp 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 -.Nm ping +.Nm during normal operations or from automated scripts. .Sh ICMP PACKET DETAILS An IP header without options is 20 bytes. An .Tn ICMP .Tn ECHO_REQUEST -packet contains an additional 8 bytes worth -of +packet contains an additional 8 bytes worth of .Tn ICMP header followed by an arbitrary amount of data. When a .Ar packetsize -is given, this indicated the size of this extra piece of data (the -default is 56). +is given, this indicated the size of this extra piece of data +.Pq the default is 56 . Thus the amount of data received inside of an IP packet of type .Tn ICMP .Tn ECHO_REPLY will always be 8 bytes more than the requested data space -(the -.Tn ICMP -header). +.Pq the Tn ICMP header . .Pp If the data space is at least eight bytes large, -.Nm ping +.Nm 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 @@ -246,8 +256,9 @@ 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 +Duplicates may occur in many situations and are rarely +.Pq 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 @@ -256,30 +267,40 @@ to the same request. Damaged packets are obviously serious cause for alarm and often indicate broken hardware somewhere in the .Nm ping -packet's path (in the network or in the hosts). +.No packet Ap s path +.Pq in the network or in the hosts . .Sh TRYING DIFFERENT DATA PATTERNS -The (inter)network layer should never treat packets differently depending -on the data contained in the data portion. +The +.Po +inter +.Pc Ns 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 +.No that doesn Ap t have sufficient +.Dq transitions , +such as all ones or all zeros, or a pattern right at the edge, such as +almost all zeros. +.No It isn Ap t +necessarily enough to specify a data pattern of all zeros +.Pq 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. .Pp 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. +If you are lucky, you may manage to find a file that either +.No can Ap 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 .Fl p option of -.Nm ping . +.Nm Ns . .Sh TTL DETAILS The .Tn TTL @@ -296,11 +317,8 @@ specification states that the .Tn TTL field for .Tn TCP -packets should -be set to 60, but many systems use smaller values (4.3 -.Tn BSD -uses 30, 4.2 used -15). +packets should be set to 60, but many systems use smaller values +.Pq Bx 4.3 \ uses 30, Bx 4.2 \ used 15 . .Pp The maximum possible value of this field is 255, and most Unix systems set the @@ -308,8 +326,9 @@ the field of .Tn ICMP ECHO_REQUEST packets to 255. -This is why you will find you can ``ping'' some hosts, but not reach them -with +This is why you will find you can +.Dq ping +some hosts, but not reach them with .Xr telnet 1 or .Xr ftp 1 . @@ -334,11 +353,11 @@ In this case the .Tn TTL value in the received packet will be 255 minus the number of routers in the path -.Xr from +.Em from the remote system .Em to the -.Nm ping Ns Em ing +.Nm Ns Em ing host. .It Set it to some other value. @@ -351,7 +370,7 @@ Others may use completely wild values. .El .Sh RETURN VALUES The -.Nm ping +.Nm command returns an exit status of zero if at least one response was heard from the specified .Ar host ; @@ -381,9 +400,9 @@ option. .Pp The maximum IP header length is too small for options like .Tn RECORD_ROUTE -to -be completely useful. -There's not much that can be done about this, however. +to be completely useful. +.No There Ap s +not much that can be done about this, however. .Pp Flood pinging is not recommended in general, and flood pinging the broadcast address should only be done under very controlled conditions. |