Option 82 AID
Ray Phillips
r.phillips at uq.edu.au
Fri Sep 18 08:00:07 UTC 2009
Recently dhcp snooping was enabled on our Cisco switches so I've used
some code I found on this list to log the option 82 data:
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 ",
substring (option agent.remote-id, 2, 256)));
log (info, concat( "Lease for ",
binary-to-ascii (10, 8, ".", leased-address),
" 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)));
}
which is working fine.
CID stands for Circuit ID I presume, but can someone tell me what the
abbreviation AID stands for please?
The switch's names, not their MAC addresses, are put into the Option
82 space. Since I wanted to use code that would work for any
reasonable name length I used the value 256 in the second substring
function because I couldn't find any way to calculate a string's
length. Is there some way to do that?
By the way, the dhcp-eval(5) man page contains this entry:
number
Any number between zero and the maximum representable size may be
specified as a numeric expression.
by doesn't elaborate on what the the maximum representable size might
be, so how is it defined?
Ray
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