D-Link xStack DGS-3620 Series Reference Manual page 49

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xStack DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch Web UI Reference Guide
Within each of these topologies, each switch plays a role in the Switch stack. These roles can be set by the user
per individual Switch, or if desired, can be automatically determined by the Switch stack. Three possible roles exist
when stacking with the Switch.
NOTE: When stacking is enabled (40G by default), the last two SFP+ ports are dedicated stacking
ports and cannot be used to uplink to other devices or switches. Stacking can only be
performed using these ports. When 80G stacking is enabled, the last four SFP+ ports are
dedicated stacking ports and cannot be used to uplink to other devices or switches. Stacking
can only be performed using these ports.
NOTE: In the 40G mode, the duplex ring's bandwidth can be up to 40G. In the 80G mode, the duplex
ring's bandwidth can be up to 80G.
NOTE: SIO1 is a logical stacking port pair. SIO2 is also a logical stacking port pair. A logical stacking
port pair must always be connected to the same Switch in the stack. Splitting logical stacking
port pairs between different Switches in the stack might not guarantee a stable stacking
connection. For example, using DGS-3620-28 switches with 80G stacking, connecting port 25
from Switch A to port 25 on Switch B and then connecting port 27 from Switch A to port 27 on
Switch C would cause a problem.
Primary Master – The Primary Master is the leader of the stack. It will maintain normal operations, monitor
operations and the running topology of the Stack. This switch will also assign Stack Unit IDs, synchronize
configurations and transmit commands to remaining switches in the switch stack. The Primary Master can be
manually set by assigning this Switch the highest priority (a lower number denotes a higher priority) before
physically assembling the stack, or it can be determined automatically by the stack through an election process
which determines the lowest MAC address and then will assign that switch as the Primary Master, if all priorities
are the same. The Primary master are physically displayed by the seven segment LED to the far right on the front
panel of the switch where this LED will flash between its given Box ID and 'H'.
Backup Master – The Backup Master is the backup to the Primary Master, and will take over the functions of the
Primary Master if the Primary Master fails or is removed from the Stack. It also monitors the status of neighboring
switches in the stack, will perform commands assigned to it by the Primary Master and will monitor the running
status of the Primary Master. The Backup Master can be set by the user by assigning this Switch the second
highest priority before physically assembling the stack, or it can be determined automatically by the stack through
an election process which determines the second lowest MAC address and then will assign that switch as the
Backup Master, if all priorities are the same. The Backup master are physically displayed by the seven segment
Figure 3-35 Switches stacked in an 80G Duplex Ring
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