Reference Guide

206 | Stacking
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MAC Addressing
All port interfaces in the stack use the MAC address of the management interface on the master switch.
The MAC address of the chassis in which the master Aggregator is installed is used as the stack MAC
address.
The stack continues to use the masters chassis MAC address even after a failover. The MAC address is
not refreshed until the stack is reloaded and a different unit becomes the stack master.
Stacking LAG
When you use multiple links between stack units, FTOS automatically bundles them in a stacking link
aggregation group (LAG) to provide aggregated throughput and redundancy. The stacking LAG is
established automatically and transparently by FTOS (without user configuration) after peering is detected
and behaves as follows:
The stacking LAG dynamically aggregates; it can lose link members or gain new links.
Shortest path selection inside the stack: if multiple paths exist between two units in the stack, the
shortest path is used.
Stacking VLANs
When you configure an Aggregator to operate in stacking mode (Configuring and Bringing Up a Stack),
VLANs are reconfigured as follows:
If an Aggregator port belonged to all 4094 VLANs in standalone mode (default), all VLAN
membership is removed and the port is assigned only to default VLAN 1. You must configure
additional VLAN membership as necessary.
If you had manually configured an Aggregator port to belong to one or more VLANs (non-default) in
standalone mode, the VLAN configuration is retained in stacking mode only on the master switch.
When you reconfigure an Aggregator from stacking to standalone mode:
Aggregator ports that you manually configured for VLAN membership in stacking mode retain their
VLAN configuration in standalone mode.
To restore the default auto-VLAN mode of operation (in which all ports are members of all 4094
VLANs) on a port, enter the auto vlan command; for example:
FTOS(conf)# interface tengigabitethernet 0/2
FTOS(conf-if-te-0/2)# auto vlan