NAME

linkloop − verify LAN connectivity with link level loopback

SYNOPSIS

linkloop [ −n count ] [ −f devfile ] [ −t timeout ] [ −s size ] [ −v ] linkaddr1 [ linkaddr2 ... ]

DESCRIPTION

Linkloop uses IEEE 802.3 link level test frames to check connectivity within a local area network (LAN).  This program differs from the remote loopback capability of landiag(1M) in that it only tests the link level connectivity, and not that of the transport. 

Super-user status is required to execute linkloop.

The required parameter is the link level address (linkaddr1, linkaddr2,...  ) of a remote node.  Linkloop tests the connectivity of the local node and the remote node specified by the link level address.  The link level address of a remote node can be found by executing the landiag program on the remote node.  In the "Local LAN Interface Status" mode of landiag, execute the display command to list the link address.  This link level address is usually represented as a hexadecimal string prefixed with 0x (but can also be represented as a octal string prefixed with 0 or as a decimal string).  The address must not be a multicast or broadcast address (the least significant bit of the first byte of the link address must be set to be zero). 

The options are:

−n count Sets the number of frames to transmit.  If count is zero, linkloop transfers frames indefinitely until an interrupt signal is received (hit the break key).  The default value for count is one. 

−t timeout Sets the amount of time (in seconds) to wait for a reply from the remote node before giving up.  If timeout is zero, linkloop waits indefinitely for a reply.  The default value for timeout is 2 seconds. 

−s size Sets the size of the data to send.  The maximum data size is 1497, which is also the default size. 

−v Sets the verbose option.  In addition to the regular summary of test results, this option causes the display of more extensive error information.  If there are header or length errors, appropriate messages are displayed.  All verbose output is preceded by the number of replies accepted before an error occurred. 

−f devfile Specifies which device file to use.  The device file must be an IEEE 802.3 device file.  If no device file is entered, linkloop uses /dev/lan as the default.  If /dev/lan is not present or is the wrong type of device file, then linkloop uses /dev/ieee as the default. 

The linkloop program can be aborted with the interrupt signal.  If aborted, the current results are printed. 
 

Linkloop prints the result of the loopback test.  If the test fails, it prints a summary of the test and indicates the type of error.  The possible messages are:

address has bad format Link address entered on the command line has bad format. 

address is not individual Link address entered on the command line does not have the least significant bit of the first byte set to 0. 

frames sent Total number of frames sent. 

frames received correctly Total number of frames received without errors. 

frames with length error Received frame length does not match transmitted frame length.  If the verbose option is set, the length received is printed. 

frames with data error Received frame does not match transmitted frame. 

frames with header error Number of frames received containing unexpected frame header information. Either the source address does not match the remote address, the destination address does not match the local address or the control field is not the TEST frame control field.  These frames are ignored.  Linkloop continues to try to receive the reply frame until the read operation times out. 

reads that timed out Count of how many read operations timed out before the reply was received. 

DIAGNOSTICS

illegal count parameter Count is not a non-negative integer or the number specified is too large for the local computer. 

illegal timeout parameter Timeout is not a non-negative integer or the number specified multiplied by 1000 is too large for the local computer. 

illegal size parameter Size specified is not in the range of 0..1497. 

unable to use device file 1. Specified device file does not exist or is of the wrong type. 
2. Linkloop is already being executed by another user. 

unable to use default device file 1. Default device file does not exist or is of the wrong type. 
2. Linkloop is already being executed by another user. 

must be super user You must have super user capabilities to execute the linkloop program. 

DEPENDENCIES

Implemented on the Series 300 only. 

AUTHOR

HP

FILES

/dev/lan first default device file

/dev/ieee second default device file

SEE ALSO

landiag(1M), lan(4). 
 

Hewlett-Packard Company  —  May 11, 2021