Palo Alto Networks firewalls support Link Layer Discovery
Protocol (LLDP), which functions at the link layer to discover neighboring
devices and their capabilities. LLDP allows the firewall and other
network devices to send and receive LLDP data units (LLDPDUs) to
and from neighbors. The receiving device stores the information in
a MIB, which the Simple Network Management Protocol (SNMP) can access.
LLDP makes troubleshooting easier, especially for virtual wire deployments
where the firewall would typically go undetected by a ping or traceroute.