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Network Discovery 
RS400 
213 
ROS™  v3.5 
10 Network Discovery 
Network Discovery is based on LLDP (Link Layer Discovery Protocol) as defined by the IEEE 
802.1AB standard. This feature provides the ability to: 
•  Enable LLDP per device and per port 
• View 
LLDP 
statistics 
•  View neighbor information 
•  Report LLDP data via SNMP 
 
10.1 LLDP Operation 
The IEEE standard, 802.1AB Link Layer Discovery Protocol (LLDP), promises to simplify 
troubleshooting of enterprise networks and enhance the ability of network management tools to 
discover and maintain accurate network topologies in multi-vendor environments. LLDP data 
are made available to NMS (Network Management Systems) via SNMP (LLDP-MIB is 
supported). 
LLDP is a neighbor discovery protocol. It defines a standard method for Ethernet network 
devices such as switches and routers to advertise information about themselves to other nodes 
on the network and to store the information they discover. Details such as device configuration, 
device capabilities and device identification can be advertised using this protocol. 
LLDP agent operation is typically implemented as two modules: the LLDP transmit module and 
LLDP receive module. The LLDP transmit module, when enabled, sends the local device's 
information at regular intervals, in 802.1AB standard format. Whenever the transmit module is 
disabled, it transmits an LLDPDU (LLDP data unit) with a time-to-live (TTL) TLV containing "0" 
in the information field. This enables remote devices to remove the information associated with 
the local device in their databases. The LLDP receive module, when enabled, receives remote 
devices’ information and updates its LLDP database of remote systems. When new or updated 
information is received, the receive module initiates a timer for the valid duration indicated by 
the TTL TLV in the received LLDPDU. A remote system's information is removed from the 
database when an LLDPDU is received from it with TTL TLV containing "0" in its information 
field.  
LLDP is implemented to keep a record of only one device per Ethernet port. Therefore, if there 
are multiple devices sending LLDP information to a switch port on which LLDP is enabled, 
information about the neighbor on that port will change constantly.