Appendix A: MSTP Overview
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Figure 143. CIST and VLAN Guideline - Example 2When port 3 on switch B receives a BPDU, the switch notes the port sending the packet belongs only to CIST 0. Therefore, switch B uses CIST 0 in determining whether a loop exists. The result would be that the switch detects a loop because the other port is also receiving BPDU packets from CIST 0. Switch B would block port 3 to cancel the loop.To avoid this issue, always assign all VLANs on a switch, including the Default VLAN, to an MSTI. This guarantees that all ports on the switch have an MSTI ID and helps to ensure that loop detection is based on MSTI, not CIST.1357911
1315
AT-GS950/16PSGigabit Ethernet PoE+ Switch
plus1357911
1315R
246 81012 14 16R 1516
1357
2468
9 11 13 15R
10 12 14 16R
15 16
100 LINKACT
1000 LINK
SFP
ACT
CLASS 1
LASER PRODUCT
SFP
PD ERRPD ON
ACT1000 LINK
ACT10/100 LINK
PORT ACTIVITY
POE MAX
SYSTEM
POE
1357911
1315
AT-GS950/16PSGigabit Ethernet PoE+ Switch
plus1357911
1315R
246 81012 14 16R 1516
1357
2468
9 11 13 15R
10 12 14 16R
15 16
100 LINKACT
1000 LINK
SFP
ACT
CLASS 1
LASER PRODUCT
SFP
PD ERRPD ON
ACT1000 LINK
ACT10/100 LINK
PORT ACTIVITY
POE MAX
SYSTEM
POE
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