XRPi Documentation - Sysop Commands

MPORT

Command

MPORT -- Select which port(s) to monitor (trace)

Synopsis

MP[ORT] [0-FFFFFFFF | p+p+p | ALL | NONE]

Description

The MPORT command selects which port(s) will be monitored when traffic tracing is enabled.

The optional argument is either a HEX number between 0 and FFFFFFFF, a list of port numbers concatenated with "+", or the words ALL or NONE.

If no argument is supplied, the current setting is reported. The hex form is preferable when monitoring is to be enabled on many ports at once, but it only works up to port 31. The hex value is calculated by adding together the desired values from this table (see MORE INFO for details of hex arithmetic):

        Port HEX    Port HEX     Port HEX     Port HEX
        ------------------------------------------------------
         0    1      8   100     16  10000    24   1000000
         1    2      9   200     17  20000    25   2000000
         2    4     10   400     18  40000    26   4000000
         3    8     11   800     19  80000    27   8000000
         4   10     12  1000     20 100000    28  10000000
         5   20     13  2000     21 200000    29  20000000
         6   40     14  4000     22 400000    30  40000000
         7   80     15  8000     23 800000    31  80000000

The P+P+P form is preferable when selecting a small number of ports to momitor, or when monitoring ports above 31.

This command duplicates the function of the <F3> key.

When a remote sysop enables tracing, the MPORT setting is cleared to NONE, to avoid overloading the link with traffic which might otherwise prevent him from issuing further commands. The remote sysop must therefor always issue the MON ON command first, followed by the MPORT command to select which port(s) to monitor.

The console can override a remote sysop's settings.

Examples

MPORT 800  -  Trace port 11.
MPORT 1803 -  Trace ports 12, 11, 2 and 1.
MPORT 1+5+39 - Trace ports 1, 5 and 39

Notes

Port zero is a "pseudo-port" used to trace traffic coming and going via Windows' TCP/IP stack. So "MPORT 0" traces port 0, instead of disabling tracing. You must use "MPORT NONE" to disable tracing - or just use MON OFF.

Limitations

Only one remote sysop may receive the trace display at any one time. Remote sysops are prevented from tracing activity on the port on which they are uplinked, because this would cause an endless loop.

Ports > 31 can only be traced using the P+P+P argument form.

Caveats

Remote sysops must ensure that their link with the router is capable of carrying the large volume of traffic resulting from tracing. Attempting to trace too many ports / too much detail on a slow link may result in poor performance. You have been warned!

More info

Hexadecimal arithmetic is based on powers of 16, and uses numbers 0-9 and letters A-F to represent numbers up to 15 as follows:

        Hex: 0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F  
        Dec: 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15

Single "digits" are added / subtracted in the usual way, except for the fact that letters represent 10-15, therefore:

The result of adding 1 and 4 is (unsurprisingly) 5 The result of adding 4 and 8 is C (decimal 12) The result of subtracting 8 from F (decimal 15) is 7

Things get more complicated when the result of a calculation is greater than 15, but fortunately that never happens when adding MPORT values.

To create a composite MPORT value, simply add the desired values from each column. For example, to monitor ports 1,2,3 6 and 7, the hex values 02, 04, 08, 40, and 80 must be added.

           02
         + 04
         + 08
         + 40  (note this is "Four zero", not "forty")
         + 80  (eight zero means "8 times 16 plus zero")
        ------
         = CE  (the decimal equivalent is (12*16)+14 = 206)
        ------

Availability

The MPORT command is available only to console and remote sysops.

See also

MONITOR(2) -- Enable / disable monitoring.
MMASK(2) -- Select type of activity to monitor.
MTO(2) -- Selective monitoring