Configuring lldp, Lldp overview, Layer 2 topology mapping – Brocade Network OS Administrator’s Guide v4.1.1 User Manual
Page 449
Configuring LLDP
LLDP overview
The IEEE 802.1AB Link Layer Discovery Protocol (LLDP) enhances the ability of network management
tools to discover and maintain accurate network topologies and simplify LAN troubleshooting in multi-
vendor environments. To efficiently and effectively operate the various devices in a LAN you must
ensure the correct and valid configuration of the protocols and applications that are enabled on these
devices. With Layer 2 networks expanding dramatically, it is difficult for a network administrator to
statically monitor and configure each device in the network.
Using LLDP, network devices such as routers and switches advertise information about themselves to
other network devices and store the information they discover. Details such as device configuration,
device capabilities, and device identification are advertised. LLDP defines the following:
• A common set of advertisement messages.
• A protocol for transmitting the advertisements.
• A method for storing the information contained in received advertisements.
NOTE
LLDP runs over the data-link layer which allows two devices running different network layer protocols to
learn about each other.
LLDP information is transmitted periodically and stored for a finite period. Every time a device receives
an LLDP advertisement frame, it stores the information and initializes a timer. If the timer reaches the
time to live (TTL) value, the LLDP device deletes the stored information ensuring that only valid and
current LLDP information is stored in network devices and is available to network management
systems.
Layer 2 topology mapping
The LLDP protocol lets network management systems accurately discover and model Layer 2 network
topologies. As LLDP devices transmit and receive advertisements, the devices store information they
discover about their neighbors. Advertisement data such as a neighbor's management address, device
type, and port identification is useful in determining what neighboring devices are in the network.
NOTE
The Brocade LLDP implementation supports up to two neighbors.
The higher level management tools, such as the Brocade Network Advisor, can query the LLDP
information to draw Layer 2 physical topologies. The management tools can continue to query a
neighboring device through the device’s management address provided in the LLDP information
exchange. As this process is repeated, the complete Layer 2 topology is mapped.
Network OS Administrator’s Guide
449
53-1003225-04