I am learning about LLDP protocol and have stumbled across terms chassis ID and port ID. If I understand correctly they can be used by network management systems to determine connections between various devices in the network.
Question:
Where does the system get its chassis ID from?
AFAIK there is no way to get a per-device unique identifier (for every possible device model). Also, on an Extreme switch I queried for SNMP OID 1.0.8802.1.1.2.1.3.2 (LLDP_LOC_CHASSIS_ID) I got back 6 bytes which seems a bit short for a worldwide device identifier. Am I missing something? Is chassis ID just some random number and implementators figured that the likelihood of collision was too low to worry about?
Bonus question 1:
At what point is LLDP chassis ID initialized? My guess is that it shouldn't change even if LLDP is disabled and then re-enabled. If this is so, is it possible to get it somehow even if LLDP is disabled?
Bonus question 2:
Does LLDP chassis ID change if you use another LLDP daemon?
A Chassis ID is not designed to be a vendor unique identifier, and the value of LLDP's Chassis Type relates to what the Chassis ID actually is, I'd wager the 6 bytes you see are the MAC address of the switch.