dhcp option 82 information

Glenn Satchell Glenn.Satchell at uniq.com.au
Wed Aug 26 12:48:00 UTC 2009

>Date: Tue, 25 Aug 2009 21:33:58 -0400 (Eastern Daylight Time)
>From: Mike Diggins <mike.diggins at McMaster.CA>
>To: dhcp-users at lists.isc.org
>Subject: dhcp option 82 information 
>My routers insert dhcp option 82 information into the DHCP requests so 
>that my DHCP server knows what switch and port the request came from. Does 
>anyone have an ISC DHCPd configuration that will extract that info and log 
>it to syslog? I had been using this with RHEL4, but in RHEL5 64 bit, it 
>doesn't quite work as expected.
># Log something useful if dhcp option 82 information is present
>if exists agent.circuit-id
>   log ( info, concat( "Lease for ", binary-to-ascii (10, 8, ".", 
>leased-address), " is connected to interface ",
>   binary-to-ascii (10, 8, "/", suffix ( option agent.circuit-id, 2)), ", 
>VLAN ",
>   binary-to-ascii (10, 16, "", substring( option agent.circuit-id, 2, 2)), 
>" on switch ",
>   binary-to-ascii(16, 8, ":", substring( option agent.remote-id, 2, 6))));
>   log ( info, concat( "Lease for ", binary-to-ascii (10, 8, ".", 
>   " raw option-82 info is CID: ", binary-to-ascii (10, 8, ".", option 
>agent.circuit-id), " AID: ",
>   binary-to-ascii(16, 8, ".", option agent.remote-id)));

What if any log entries are you getting?

What facility and priority is set in dhcpd.conf and /etc/syslog.conf?
There may be a mismatch with the upgraded OS.

This is from dhcpd.conf man page for 4.1.1b1 (may be different on older
releases, in particular the default facility)

       log-facility facility;

       This statement causes the DHCP server to  do  all  of  its
       logging  on the specified log facility once the dhcpd.conf
       file has been read.   By default the DHCP server  logs  to
       the  daemon  facility.    Possible  log facilities include
       auth, authpriv, cron, daemon, ftp, kern, lpr, mail,  mark,
       news,  ntp,  security,  syslog,  user,  uucp,  and  local0
       through local7.   Not all of these facilities  are  avail-
       able  on  all  systems,  and there may be other facilities
       available on other systems.

       In addition to setting this value, you may need to  modify
       your  syslog.conf  file  to  configure logging of the DHCP
       server.   For example, you might add a line like this:

            local7.debug /var/log/dhcpd.log


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