Virtual local area networks (VLANs) are used to group end-system hosts into the same broadcast domain. The hosts on a VLAN might not reside on the same LAN, but even if they do, each host can communicate with another host by using Layer 2 (L2) protocols. Conversely, hosts that reside on the same LAN but different VLANs cannot communicate by using L2 protocols. Each host that resides on a VLAN uses a network interface to communicate with other hosts on the VLAN. VLANs are identified by VLAN identifiers (VIDs) that are exported by LLDP daemons over the relevant network interfaces to their peers. These peers are typically network devices, for example, switches that use a VID to forward data packets to respective hosts.
Hosts might not receive the intended packets if the VIDs are not configured correctly on the relevant network interfaces. The VLAN ID mismatch monitor captures this type of misconfiguration because it verifies the VID information whenever the VLAN information is modified, at system boot time and periodically. If the VID for an interface changes, the appropriate ireport messages are generated. Because the VLAN information is verified by using LLDP packets, the peer host needs to have the LLDP service enabled. See Chapter 5, Exchanging Network Connectivity Information With Link Layer Discovery Protocol, in Managing Network Datalinks in Oracle Solaris 11.2 .