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cdpd(8)                DragonFly System Manager's Manual               cdpd(8)


NAME

     cdpd - Send CDP/LLDP packets over ethernet.


SYNOPSIS

     cdpd [-d] [-i interface] [-h] [-t period] [-o] [-a] [-l] [-c] [-r]


DESCRIPTION

     The cdpd utiliy used to advertize your host over ethernet networks using
     CDP (Cisco Discovery Protocol) and LLDP (Link Layer Discovery Protocol,
     802.1ab) protocols.

     The options are as follows:

     -d      increase debugging level and do not daemonise, as debug goes on
             stdout

     -i interface
             set interface, over which packets will be sent

     -h      get help message

     -t period
             set the period between packets sent (60 sec by default)

     -o      sent only one announce per interface (well, two in case of both
             CDP and LLDP enabled) and then exit

     -a      try to add all iinterfaces with ip addresses configured to those
             added with -i option

     -c      do NOT send CDP packets (enabled by default).

     -l      do NOT send LLDP packets (enabled by default).

     -r      announce host as Router-capable device (Station-capable and
             -enabled by default).  Extra flag needed because 802.1AB
             specifies that 'The station only capability is intended for
             devices that implement only an end station capability.  Bit 7
             should not be set in conjunction with any other bits.', and, at
             least Cisco IOS 12.2(46)SE ignores capabilities consisting of
             Router and Station bits set together.


DIAGNOSTICS

     When everything is ok, and cdpd program is started with (default) daemon
     mode, it justs daemonises with return code 0.  In case of errors they are
     printed to stderr and program exists with non-zero status. Most errors
     caused by the fact that the cdpd needs access to /dev/bpf*, so it must be
     started by root, and Berkeley Packet Filter must be enabled in kernel (by
     adding pseudo-device bpf into kernel configuration for old FreeBSD, for
     example).


ADDITIONAL NOTE

     Some people proposed option of collecting information from an ethernet
     interfaces to have some table like cisco 'show cdp nei' command output.
     But, as you can retrieve this information from modern tcpdump program
     (with -nvi <interface> -s 1500 ether dst 01:00:0c:cc:cc:cc flags) and as
     this feature leads to expensive CPU usage, this feature will not be
     implemented in cdpd.

     The same trick can be used to detect LLDP neighbors, the only difference
     is that destination MAC address is ether dst 01:80:c2:00:00:0e


BUGS

     When running on Solaris, self mac-address is not determined correctly, so
     it announced via LLDP as 00:00:00:00:00:00. This can be fixed.


SEE ALSO

     http://www.cisco.com/ for information about Cisco Discovery Protocol.

     http://www.ieee802.org/1/pages/802.1ab.html
     http://en.wikipedia.org/wiki/Link_Layer_Discovery_Protocol for
     information on LLDP/802.1AB.

     http://www.tcpdump.org/ - tcpdump home page.


AUTHOR

     Alexandre Snarskii, <snar@snar.spb.ru>

                               December 1, 2008

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