3Com SuperStack 4 Configuration Manual page 419

XRN Features
Distributed Device
Management (DDM)
Distributed Resilient
Routing (DRR)
Switching capacity that increases as you add a Switch to the Fabric. So
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network performance and resilience expand as the Fabric grows.
Link Aggregation supported across the Distributed Fabric.
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Flexibility provided by:
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Support across any of the Switches within an individual SuperStack 4 Switch
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5500G-EI family to create an XRN Distributed Fabric.
This section describes the key features of XRN.
DDM provides single IP address management across the interconnected Switches
that form the Distributed Fabric. This allows the entire Distributed Fabric to be
managed and configured as a single managed entity. In the event of failure in one
of the Switches in the Distributed Fabric, management access to the remaining
Switch is retained on the same IP address.
DDM allows you to manage the Distributed Fabric via the command line
interface (CLI), Web interface, or SNMP.
DDM provides you with the ability to carry out the following:
Single step Switch software upgrades across the Distributed Fabric (provided
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the Switches are of the same family).
Distributed Fabric-wide configuration of all software features.
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Configuration of port-specific software features across the Distributed Fabric
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via a single management interface.
DRR allows the Switches in the Distributed Fabric to act as a single logical router
which provides router resiliency in the event of failure in one of the interconnected
Switches. With DRR, Switches in the Distributed Fabric are routing, which
significantly increases the overall Layer 3 capacity of the core of the network.
DRR can intelligently distribute the routing load across both Switches in the
Distributed Fabric, which maximizes routing performance and makes full use of
bandwidth capacity.
Switches in the Distributed Fabric provide Layer 3 local forwarding for directly
connected hosts and devices.
Switch units within the Distributed Fabric provide the same router interfaces and
mirror each other's routing tables. This allows each unit to keep the routing local
to the unit for locally connected hosts and devices.
In the example shown in
Distributed Fabric with router interfaces (R1, R2, and R3) shared by both units.
If there is a loss of a unit in an XRN Distributed Fabric it does not affect routing
provided you are using Distributed Link Aggregation or the devices in the wiring
closet are multihomed.
Figure 106, there is a single logical router across the XRN
XRN Features 431