Руководство По Проектированию для Cisco Cisco Nexus 5010 Switch
Design Guide
© 2010 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
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Top-of-the-rack topologies:
This topology consists of one-rack unit (1RU) or 2RU devices at the top or
bottom of each server rack, providing server (or blade server) connectivity within each rack and aggregated by
a switch at the aggregation layer. Top-of-the-rack topologies are more efficient in terms of cabling because
fewer cables are required from each rack to the end-of-the-row switch. On the other hand, top-of-the-rack
topologies require more switches than end-of-the-row topologies require for the same number of switch ports,
which increases the management burden.
a switch at the aggregation layer. Top-of-the-rack topologies are more efficient in terms of cabling because
fewer cables are required from each rack to the end-of-the-row switch. On the other hand, top-of-the-rack
topologies require more switches than end-of-the-row topologies require for the same number of switch ports,
which increases the management burden.
Layer 2
Layer 2 has been well known for its flexibility in providing VLAN access anywhere in the data center. Layer 2 is also
known for the potential impact of Layer 2 loops. Overall, the benefits of Layer 2 largely outweigh the risk of loops, so
most environments today consist of Layer 2 pods or even have multiple pods that are part of the same Layer 2
domain.
known for the potential impact of Layer 2 loops. Overall, the benefits of Layer 2 largely outweigh the risk of loops, so
most environments today consist of Layer 2 pods or even have multiple pods that are part of the same Layer 2
domain.
A Layer 3 boundary is always recommended to connect servers to clients. The placement of the Layer 3 boundary
defines the scale of the Layer 2 domain, with the result that the size of Layer 2 domains varies enormously between
customers.
defines the scale of the Layer 2 domain, with the result that the size of Layer 2 domains varies enormously between
customers.
The factors that determine the size of Layer 2 domains include:
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The percentage of high-availability, clustered servers
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The need for virtual machine mobility
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The need to quickly provision new servers in the same subnet
The availability of new application technologies will influence new data centers toward more or less use of Layer 2,
but the current trend indicates a permanent need for a scalable Layer 2 infrastructure.
but the current trend indicates a permanent need for a scalable Layer 2 infrastructure.
Cisco is delivering technology that makes Layer 2 topologies more solid and more efficient in terms of bandwidth, and
that helps you extend Layer 2 where needed.
that helps you extend Layer 2 where needed.
V-Shape
While several network designs fit the requirements of consolidation, as well as the cabling requirements of end-of-
the-row or top-of-the-rack topologies, the most widely deployed network design model is referred to as “V-shape,”
whereby each “access” switch is dual-homed to the aggregation layer, and Spanning Tree Protocol keeps the
topology free from loops.
the-row or top-of-the-rack topologies, the most widely deployed network design model is referred to as “V-shape,”
whereby each “access” switch is dual-homed to the aggregation layer, and Spanning Tree Protocol keeps the
topology free from loops.
Common Designs
Figure 1 illustrates a legacy design.