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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.