Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 70)

You can use topology groups with the following Layer 2 protocols:
• STP/RSTP
• MRP
• VSRP
• 802.1W
Topology groups simplify Layer 2 configuration and provide scalability by enabling you to use the
same instance of a Layer 2 protocol for multiple VLANs. For example, if a Brocade device is deployed
in a Metro network and provides forwarding for two MRP rings that each contain 128 VLANs, you can
configure a topology group for each ring. If a link failure in a ring causes a topology change, the
change is applied to all the VLANs in the ring topology group. Without topology groups, you would
need to configure a separate ring for each VLAN.
Master VLAN and member VLANs
Each topology group contains a master VLAN and can contain one or more member VLANs and
VLAN groups:
• 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 MRP, the topology group master VLAN
contains the ring 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 Layer 2 protocol configuration or Layer 2 topology
affects all the member VLANs. Member VLANs do not independently run a Layer 2 protocol.
• Member VLAN groups - A VLAN group is a named set of VLANs. The VLANs within a VLAN group
have the same ports and use the same values for other VLAN parameters.
When a Layer 2 topology change occurs on a port in the master VLAN, the same change is applied to
that port in all the member VLANs that contain the 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 that contain that port. However, the state change does not affect port 1/1 in
VLANs that are not members of the topology group.
Control ports and free ports
A port that is in a topology group can be a control port or a free port:
• Control port - A control port is a port in the master VLAN, and is therefore controlled by the Layer 2
protocol configured in the master VLAN. The same port in all the member VLANs is controlled by
the master VLAN Layer 2 protocol. Each member VLAN must contain all of the control ports and
can contain additional ports.
• Free port - A free port is not controlled by the master VLAN Layer 2 protocol. The master VLAN can
contain free ports. (In this case, the Layer 2 protocol is disabled on those ports.) In addition, any
ports in the member VLANs that are not also in the master VLAN are free ports.
NOTE
Since free ports are not controlled by the master port Layer 2 protocol, they are assumed to always be
in the Forwarding state.
Master VLAN and member VLANs
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