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Chapter 2: Virtual Chassis Stacking
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VCStack Introduction
Virtual Chassis Stacking (VCStack™) is the name given to two or more
separate Allied Telesis switches that are configured to operate as a single
logical switch. The VCStack operates as a single device and is not
perceived by end users, or the traffic itself, to be any more than a single
network node. From a configuration and management point of view, it is as
though the switches are one device with a seamless transition from the
ports of one stack member to the ports of the next.
Each component switch in a VCStack is called a stack member. The
VCStack also contains one stack master, which is the switch that
manages the stack. To function as a VCStack the component switches are
connected using high-speed stacking links.
When configuring a VCStack, there are no limitations on how the ports on
one stack member can interact with the ports of another stack member.
VLANs, port aggregations, port mirroring, and port ranges in the
configuration can all span multiple stack members. The stack member
ports truly operate as though they all belong to one virtual switch. The
same applies with Layer 2 and Layer 3 switching (both unicast and
multicast).
A VCStack may also include a resiliency link, which is an extra,
out-of-band, data link between stack members. In the event of loss of
communication across the stacking connection, the stack members can
determine the status of other members via communication on the
resiliency link. This assists the stack members in deciding the correct
course of action when communication on the stack is lost.
For more information about Virtual Chassis Stacking (VCStack™) see the
Stacking Introduction and Stacking Commands chapters in the AlliedWare
Plus
Operating System Software Reference from www.alliedtelesis.com.
Features of
VCStacking
Creating a VCStack greatly eases network management, because you
can configure all the stacked devices via a single IP address. Creating a
VCStack will often eliminate your need to configure protocols such as
VRRP and Spanning Tree. VCStack also enables you to create highly
resilient networks. This resiliency can be applied in several ways.
Within the stack itself, switch interconnection is via two links. The second
link is able to provide an alternative data path, so the stack continues to
function if a single link fails. User ports can also be made extremely
resilient by utilizing link aggregation. Aggregated links can span ports,
modules, and even switches within the stack. Creating aggregated links
that span multiple switches within a stack creates a resilient configuration.
Communication will still exist even if a switch and its aggregated ports fail.