Allied Telesis AT-GS920/16, Installation And User Manual

Page: 115 / 118

Chapter : Loop Prevention Feature
115
When a loop is detected in the example shown in Figure 67 on page 115,
Port 2 on the Switch C is blocked to relieve the loop. Port 2 on Switch C
and Port 6 on Switch B have the same hop count and both ports are
connected to an AT-GS920/8 switch, which means the same switch
priority. However, the MAC address of Switch C is larger than the MAC
address of Switch B. Therefore, Port 2 on Switch C is chosen to be
blocked.
Figure 67. Case 3: Selecting a Port to be Blocked
Port Blocked on
One Switch
When a loop occurs within one GS920 Series switch, all the ports have the
same hop count, same switch priority, and same MAC address. Loop
Prevention selects a port to block based on the port numbers.
When a loop occurs within one AT-GS920/8 switch, Loop Prevention
blocks the port with the smaller port number. See Figure 68 as an
example.
Figure 68. Blocked Port on One AT-GS920/8 Switch
When a loop occurs within one AT-GS920/16 or AT-GS920/24 switch,
Loop Prevention blocks the port with the larger port number. See
Figure 69 as examples.
Figure 69. Blocked Port on One AT-GS920/16 or AT-GS920/24 Switch