Master VLAN, member VLANs, and bridge-domains

Each topology group contains a master VLAN and can contain one or more member VLANs and bridge-domains. A definition for each of these VLAN types follows:

• Master VLAN—The master VLAN contains the configuration information for the Layer 2 protocol. For example, if you plan to use the topology group for Rapid per VLAN Spanning tree (R-PVST), the topology group‘s master VLAN contains the R-PVST configuration information.
• Member VLANs—The member VLANs are additional VLANs that share ports with the master VLAN. The Layer 2 protocol settings for the ports in the master VLAN apply to the same ports in the member VLANs. A change to the master VLAN‘s Layer 2 protocol configuration or Layer 2 topology affects all the member VLANs. Member VLANs do not independently run a Layer 2 protocol.
• Member bridge domains—The member bridge domains are similar to VLANs that share ports with the master VLAN. The Layer 2 protocol settings for the ports in the master VLAN apply to the same ports in the bridge domains. A change to the master VLAN's Layer 2 protocol configuration or Layer 2 topology affects all the bridge domains. Bridge domains do not independently run a Layer 2 protocol. In a bridge domain, a single port can have multiple logical interfaces. In this scenario, all the logical interfaces on that port (and bridge domain) will follow the state of master VLAN port.

When a Layer 2 topology change occurs, resulting in a change of port state in the master VLAN, the same port state is applied to all the member VLANs and bridge-domains belonging to the topology group on that port. For example, if you configure a topology group whose master VLAN contains ports 1/1 and 1/2, a Layer 2 state change on port 1/1 applies to port 1/1 in all the member VLANs and bridge-domains that contain that port. However, the state change does not affect port 1/1 in VLANs that are not members of the topology group.