Owner's Manual

528 | Chapter 18. STP
NETGEAR 8800 User Manual
If you configure EMISTP or PVST+, the STPD ID must be identical to the VLAN ID of the
carrier VLAN in that STPD. See
Specifying the Carrier VLAN on page 528 for an example.
If you have an 802.1D configuration, NETGEAR recommends that you configure the StpdID
to be identical to the VLAN ID of the carrier VLAN in that STPD. See
Basic 802.1D
Configuration Example on page 575 for an example.
If you configure Multiple Spanning Tree (MSTP—IEEE 802.1Q-2003, formerly IEEE 802.1s)
you do not need carrier VLANs for MSTP operation. With MSTP, you configure a Common
and Internal Spanning Tree (CIST) that controls the connectivity of interconnecting MSTP
regions and sends BPDUs across the regions to communicate the status of MSTP regions.
All VLANs participating in the MSTP region have the same privileges. For more information
about MSTP, see
Multiple Spanning Tree Protocol on page 557.
Protected VLAN
Protected VLANs are all other VLANs that are members of the STPD. These VLANs
“piggyback” on the carrier VLAN. Protected VLANs do not transmit or receive STP BPDUs,
but they are affected by STP state changes and inherit the state of the carrier VLAN.
Protected VLANs can participate in multiple STPDs, but any particular port in the VLAN can
belong to only one STPD. Also known as non-carrier VLANs.
If you configure MSTP, all member VLANs in an MSTP region are protected VLANs. These
VLANs do not transmit or receive STP BPDUs, but they are affected by STP state changes
communicated by the CIST to the MSTP regions. Multiple spanning tree instances (MSTIs)
cannot share the same protected VLAN; however, any port in a protected VLAN can belong
to multiple MSTIs. For more information about MSTP, see
Multiple Spanning Tree Protocol on
page 557.
Specifying the Carrier VLAN
The following example:
• Creates and enables an STPD named s8.
• Creates a carrier VLAN named v5.
• Assigns VLAN v5 to STPD s8.
• Creates the same tag ID for the VLAN and the STPD (the carrier VLAN’s ID must be
identical to the STPD’s ID).
create vlan v5
configure vlan v5 tag 100
configure vlan v5 add ports 1:1-1:20 tagged
create stpd s8
configure stpd s8 add vlan v5 ports all emistp
configure stpd s8 tag 100
enable stpd s8
Notice how the tag number for the VLAN v5 and the STPD s8 is identical (the tag is 100). By
using identical tags, you have selected the carrier VLAN. The carrier VLAN’s ID is identical to
the STPD’s ID.