cisco C3560 encoding for option agent.circuit-id

[Niall O'Reilly]

Hello.

After some Googling and visiting the archives, I'm no wiser, so I'm 
asking this list.

I'll appreciate it if anyone can refer me to where I can find a 
definition for how the vlan-module-port information is encoded
for option agent.circuit-id by Cisco C3560 switches.

Here's what I'm seeing.

VLAN 2, port Fa0/1: option agent.circuit-id 0:4:0:2:1:3;
VLAN 2, port Fa0/3: option agent.circuit-id 0:4:0:2:1:5;
VLAN 2, port Fa0/17: option agent.circuit-id 0:4:0:2:1:13;

I've seen mentioned in the archives an off-by-one issue, but I
read it as low-by-one; here I'm seeing high-by-one for the module,
and high-by-two for the port.

In case it's relevant, here's the first line of the output
from 'show version'

Cisco IOS Software, C3560 Software (C3560-IPBASEK9-M),
  Version 12.2(50)SE1, RELEASE SOFTWARE (fc2)

Thanks in advance.

/Niall