The Link Layer Discovery Protocol is a vendor-neutral link layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network, principally wired Ethernet.

Ideally, this is great to use to make sure that switches are talking to each other prior to creating trunk ports.

The default setting for LLDP on the Cisco (and Juniper) devices are all we need to ensure that devices are talking to each other.

ON CISCO DEVICE:

1. Log into switch either via SSH or console connection and type in the following commands.
2. configure terminal
3. lldp run
4. wr mem (or: copy run-start)

To verifiy the LLDP connection…

1. show lldp neighbors

ON JUNIPER DEVICE:

1. Log into switch either via SSH or console connection and type in the following commands.
2. cli
3. configure
4. edit protocols lldp
5. set interface all
6. commit

To verifiy the LLDP connection… (NOTE: you must be in CLI mode and not CONFIGURATION mode)

1. show lldp neighbors