CISCO-VLAN-BRIDGING-MIB

Description: Manages VLAN-aware transparent bridging, MAC address tables, and per-VLAN spanning tree on Cisco switches.

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This MIB optimizes access to VLAN-aware transparent bridging data on Cisco switches, extending concepts from the standard RFC 1493 Bridge MIB with VLAN ID-based indexing and bitmapped encodings for frequently accessed spanning-tree and forwarding data. It exposes per-VLAN spanning tree state and forwarding map information rather than physical hardware sensors. Its monitoring value is software/protocol status, as administrators use the compact forwarding map bitmaps to quickly determine, per port and per VLAN, whether spanning tree has placed the port in a forwarding or blocking state, which is key to diagnosing Layer 2 loops or unexpected topology changes. It explicitly depends on and is modeled after the standard Bridge MIB (RFC 1493) for its baseline object model. It is deployed on Cisco Catalyst switches running VLAN-based spanning tree. Engineers can download the CISCO-VLAN-BRIDGING-MIB file directly to load it into their MIB browser.

An administrator troubleshooting a Layer 2 loop or blocked port would query cvbStpTable / cvbStpEntry for a given VLAN and decode cvbStpForwardingMap (or cvbStpForwardingMap2k for larger port counts) to see which ports are actively forwarding versus blocking under spanning tree. An unexpected bit pattern showing a normally-forwarding port now blocking would indicate a recent topology change or STP recalculation. This gives a much more efficient, per-VLAN view than polling the full standard Bridge MIB tables port by port.

Cisco VLAN bridging optimization for efficient access to RFC 1493 bridging data.