434 APPENDIX D: 3COM XRN
the Command Guide supplied in PDF format on the CD-ROM that accompanies
your Switch or on the 3Com Web site.
Important
Considerations and
Recommendations
This section contains important points and recommendations that you need to
consider or be aware of when designing a network using XRN .
■ Bandwidth across the XRN Interconnect is detailed in Tabl e 464. Intelligent
Local Forwarding and DRR ensures efficient use of bandwidth across the Fabric
Interconnect.
Table 464 Bandwidth across the XRN Interconnect
■ When you create a Distributed Fabric the relevant port-based tables do not
double in size, they remain as they were.
■ When Switch 5500G-EI units are in an XRN Distributed Fabric their unit IDs are
user configurable.
■ The maximum number of Switch units that can be interconnected is shown in
Tabl e 465.
Table 465 Number of Switch units that can create an XRN Distributed Fabric
■ It is not possible to create an XRN Distributed Fabric with Switches from
different SuperStack
4 5500 families, for example, a Switch 5500-EI with a
5500G-EI. You can only use Switches within an individual SuperStack
4 5500
family to create an XRN Distributed Fabric, for example, a Switch
5500G-EI
52-Port with a Switch 5500G-EI 28-Port.
■ 3Com strongly recommends that you upgrade all Switches to be
interconnected to the latest software agent.
■ 3Com recommends that you initialize a Switch unit that has previously been
used elsewhere in your network before you interconnect to an existing unit. If
you do not initialize the unit, problems may be caused by conflicting Switch
configurations.
■ When a port is operating in XRN mode it will no longer be configurable in the
normal way, that is, you cannot control port features such as auto-negotiation,
VLANs, static addresses, STP, Aggregated Links, Resilient Links, and so on.
Recommendations for
Achieving Maximum
Resilience
To achieve maximum network-level resilience 3Com recommends that:
■ Servers and wiring closets are multihomed. That is, each server or wiring closet
is connected to both units within the Distributed Fabric.
■ On all multi-homed links you use link aggregation (preferably configured
automatically via LACP rather than configured manually) across an XRN
Distributed Fabric, and you have STP/RSTP enabled across your network. (See
“Legacy Aggregated Links” on page 439 for more information.)
Switch Model Bandwidth across the XRN Interconnect
Switch 5500G-EI 48 Gbps, 96 Gbps (full duplex)
Switch Model Max number of units Method
Switch 5500G-EI 8 Loop
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