Prerequisites to check if VLAN not discovered or status shows Unknown.
Based on below OIDs result, we are showing VLANs information for Routers/Switches in OpManager.
For Cisco category devices, load these two mib files CISCO-VTP-MIB and CISCO-VLAN-MEMBERSHIP and check.
Open MIB browser, provide the concern device details with correct SNMP community, then provide the OID one by one to check the response.
VlanIndex - .1.3.6.1.4.1.9.9.68.1.2.2.1.2
VlanName - .1.3.6.1.4.1.9.9.46.1.3.1.1.4
VlanStatus - .1.3.6.1.4.1.9.9.68.1.1.7.1.3
For Non Cisco, load Q-BRIDGE-MIB
VlanIndex - .1.3.6.1.2.1.17.7.1.4.5.1.1
VlanName - .1.3.6.1.2.1.17.7.1.4.3.1.1
VlanStatus - .1.3.6.1.2.1.17.7.1.4.3.1.5