Netgear XCM8806 Chassis User Manual - Page 564

NETGEAR 8800 User Manual Note: If two switches are configured for the same CIST and MSTI region, in order for them to understand that they are in the same region, both must also belong to the same VLAN which is added to the STP domain. If they belong to different VLANs, each switch believes that each belongs to a different region. When an MSTP BPDU is sent, it carries a VID digest created by VLAN memberships in the CIST domain and the MSTI domain. Boundary Ports Boundary ports are bridge ports that are only connected to other MSTP regions or 802.1D or 802.1w bridges. The ports that are not at a region boundary are called internal ports. The boundary ports exchange only CIST BPDUs. A CIST BPDU originated from the CIST root enters a region through the CIST root port and egresses through boundary ports. This behavior simulates a region similar to an 802.1w bridge, which receives BPDUs on its root ports and forwards updated BPDUs on designated ports. Figure 52 shows an MSTP network that consists of two MSTP regions. Each region has its own CIST regional root and is connected to the CIST root through master ports. The CIST regional roots in each region are the MSTP bridges having the lowest CIST external root path cost. The CIST root is the bridge with the lowest bridge ID and is an 802.1w bridge outside of either MSTP region. = boundary port = master port = MSTI root port (10) CIST root bridge A C B (20) CIST regional root MSTP D Region 1 E I (40) CIST regional root, MSTI regional root MSTP Region 2 J F K (50) MSTI (60) regional root (80) (90) G H (100) EX_167 Figure 52. Sample MSTP Topology with Two MSTP Regions 564 | Chapter 18. STP