Port-Based Virtual LANs (VLANs) and GVRP

Port-Based Virtual LANs (Static VLANs)

include the link carrying the Management VLAN, which will cause loss of management access to some devices. This can also occur where meshing is configured and the Management VLAN is configured on a separate link.

VLAN 20 (Management VLAN)

Even though the ports on the Management VLAN link do not belong to any of the VLANs in the mesh, the link will be blocked if you enable Spanning Tree. This is because Spanning Tree operates per-switch and not per-VLAN.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mesh Domain

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Includes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Membership in

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Three VLANs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VLAN 10

VLAN 30

VLAN 40

Switch

 

 

 

 

Switch

 

 

 

 

2

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 11-23. Example of Inadvertently Blocking a Management VLAN Link by Implementing Spanning Tree

Effect of VLANs on Other Switch Features

Spanning Tree Operation with VLANs

Because the Series 5300XL switches follows the 802.1Q VLAN recommenda­ tion to use single-instance spanning tree, Spanning Tree operates across all ports on the switch (regardless of VLAN assignments) instead of on a per- VLAN basis. This means that if redundant physical links exist between the switch and another 802.1Q device, all but one link will be blocked, regardless of whether the redundant links are in separate VLANs. However, you can use port trunking to prevent Spanning Tree from unnecessarily blocking ports (and to improve overall network performance). Refer to “STP Operation with 802.1Q VLANs” on page 13-4.

Note that Spanning Tree operates differently in different devices. For example, in the (obsolete, non-802.1Q) HP Switch 2000 and the HP Switch 800T, Span­ ning Tree operates on a per-VLAN basis, allowing redundant physical links as long as they are in separate VLANs.

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