The Link Layer Discovery Protocol (LLDP) is an IEEE 802.1AB standard protocol used by network devices to advertise their identity and capabilities to neighboring devices on a local network.

One limitation is that LLDP must be explicitly configured and enabled on network infrastructure, such as Juniper switches, for it to operate. If it is not enabled on a specific port or globally, no discovery will occur.

Another fundamental limitation is its operational scope. LLDP functions only between directly connected devices. The LLDP data units (LLDPDUs) are link-local and are not forwarded by switches, meaning a device can only learn about its immediate neighbors, not devices further away in the topology.

B. LLDP is highly scalable because its traffic is confined to individual links and is not flooded or routed throughout the network.

D. This statement is false. While many network infrastructure devices support LLDP, a large number of end-client devices (e.g., laptops, PCs) do not.

1. Juniper Networks TechLibrary, "Understanding LLDP and LLDP-MED on EX Series Switches": This document explicitly states, "LLDP is a link-layer protocol that allows network devices to advertise their capabilities to their directly connected neighbors." This supports option C. The document also provides configuration examples, such as set protocols lldp interface ge-0/0/0, demonstrating that LLDP must be actively configured, which supports option A.

2. Juniper Mist Documentation, "Third-Party Switches": In the section for integrating non-Juniper switches, the documentation lists "Enable LLDP on all switch ports that connect to Mist APs and other switches" as a requirement for network visibility. This confirms that LLDP is a feature that requires explicit configuration (supporting option A).

3. IEEE Std 802.1AB-2016, "IEEE Standard for Local and metropolitan area networks - Station and Media Access Control Connectivity Discovery": Section 7.1, "LLDP architecture," describes the protocol's operation between adjacent systems on the same IEEE 802 LAN. The scope is inherently limited to a single physical link, which validates the "directly connected devices" limitation (supporting option C).