Arista Warrior

Chapter 8. LLDP

Link Layer Discovery Protocol (LLDP) is the open source answer to Cisco’s proprietary Cisco Discovery Protocol (CDP). LLDP is specified in IEEE 802.1AB and is similar to CDP in many ways. Let’s take a look at LLDP in action, and see what you may need to do to make it work with other vendors’ devices.

My Arista 7124S switch is connected to a Cisco 3750. The connection is between G1/0/52 on the 3750 and e24 on the Arista. When I turn up the port, I get the following message on the Arista console:

Apr 10 23:21:35 Arista Lldp: %LLDP-5-NEIGHBOR_NEW: LLDP neighbor with
chassisId 001c.b084.cfb4 and portId "[ Arista e24 ]" added on
interface Ethernet24

Without configuring anything, the Arista switch has discovered the Cisco switch, even though the Arista switch is not running CDP. Let’s dig in and see what Arista sees:

Arista#sho lldp
LLDP transmit interval      : 30 seconds
LLDP transmit holdtime      : 120 seconds
LLDP reinitialization delay : 2 seconds

Enabled optional TLVs:
  Port Description
  System Name
  System Description
  System Capabilities
  Management Address (best)
  IEEE802.1 Port VLAN ID
  IEEE802.3 Link Aggregation
  IEEE802.3 Maximum Frame Size

Port       Tx Enabled  Rx Enabled
Et1        Yes         Yes
Et2        Yes         Yes
Et3        Yes         Yes
Et4        Yes         Yes
Et5        Yes         Yes
Et6        Yes         Yes
Et7        Yes         Yes
Et8        Yes         Yes
Et9        Yes         Yes
Et10       Yes         Yes
Et11       Yes         Yes
Et12       Yes         Yes
Et13       Yes         Yes
Et14       Yes         Yes
Et15       Yes         Yes
Et16       Yes         Yes
Et17       Yes         Yes
Et18       Yes         Yes
Et19       Yes         Yes
Et20       Yes         Yes
Et21       Yes         Yes
Et22       Yes         Yes
Et23       Yes         Yes
Et24       Yes         Yes

That’s pretty ...