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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The fundamental concepts of VSS are described at the following site:
The main difference between VSS and vPC is that vPC doesn’t unify the control plane, while VSS does. Table 1
summarizes the differences between the two technologies.
summarizes the differences between the two technologies.
Table 1.
VSS Compared with vPC
Cisco VSS
Cisco vPC
Platform Support
Cisco Catalyst 6500 Virtual Switching System 1440
Cisco Nexus 7000 and Nexus 5000 Series (Cisco NX-
OS Software Release 4.1(3))
OS Software Release 4.1(3))
Control Plane
One single control plane
Separate control planes
In-Service Software Upgrade
(ISSU)
(ISSU)
Across chassis
Within a single system on the Cisco Nexus 7000 Series,
there is a mechanism to prevent unwanted vPC
configurations during ISSU.
there is a mechanism to prevent unwanted vPC
configurations during ISSU.
Configuration
Synchronization
Synchronization
Automatic
Manual, but assisted by protocol verification (Cisco
Fabric Services)
Fabric Services)
EtherChannel to Prefer Local
Links
Links
Yes (both inbound and outbound)
Yes (both inbound and outbound)
Dual-Active Detection
Yes, through Enhanced Port Aggregation Protocol
(EpagP), bidirectional forwarding detection (BFD), or
Dual-Fast Hello
(EpagP), bidirectional forwarding detection (BFD), or
Dual-Fast Hello
Yes, through fault-tolerant link (routed)
Port Channel Protocol
Link Aggregation Control Protocol (LACP), PagP
LACP
Ports in a Single Port Channel
8 without LACP, 16 (8 active, 8 standby) with LACP
8 without LACP or 16 (8 active, 8 standby) with LACP
on a single Cisco Nexus 7000 Series or 16 all active
with 8 active per Cisco Nexus 7000 Series, 16 all active
on Cisco Nexus 5000 Series
on a single Cisco Nexus 7000 Series or 16 all active
with 8 active per Cisco Nexus 7000 Series, 16 all active
on Cisco Nexus 5000 Series
Number of MCEC Supported
Up to 128 port channels per system in standalone
mode, and 512 multichassis EtherChannels in VSS
mode
mode, and 512 multichassis EtherChannels in VSS
mode
The hardware supports 768 virtual PortChannels. The
control plane supports as many as indicated in the
release notes. The number is increasing as new
releases are introduced and higher-density
configurations are tested.
480 2-port virtual PortChannels (as defined in this
document) on the Cisco Nexus 5000 Series with NX-
OS Software Release 4.1(3)
control plane supports as many as indicated in the
release notes. The number is increasing as new
releases are introduced and higher-density
configurations are tested.
480 2-port virtual PortChannels (as defined in this
document) on the Cisco Nexus 5000 Series with NX-
OS Software Release 4.1(3)
Spanning Tree Neighbors
Single switch
Single switch as seen on the vPC ports (but 2 switches
as seen on non-vPC ports)
as seen on non-vPC ports)
Cisco Discovery Protocol
Neighbors
Neighbors
One single neighbor
Each switch appears individually
Layer 2 and Layer 3 MCEC
Yes
vPC is by default a switch port, thus Layer 2
HSRP Configuration
Not required
Standard HSRP configuration, enhanced to prefer local
forwarding
forwarding
Back-to-Back MCEC
Yes Yes
Dual-Layer MCEC
Yes Yes
For more details on the vPC technology, please see Chapter 3.
Spanning Tree Protocol
Spanning Tree Protocol doesn’t disappear in vPC-based data centers. Spanning Tree Protocol still runs, except that
dual-connected switches have no port blocking.
dual-connected switches have no port blocking.
If links that are unbundled from the vPC end up in the Individual (I) state, Spanning Tree Protocol intervenes to
prevent a loop. Hence vPC-based topologies provide double protection from Layer 2 loops.
prevent a loop. Hence vPC-based topologies provide double protection from Layer 2 loops.
Just as with regular non-vPC designs, with Spanning Tree Protocol the choice between Multiple Spanning Tree
(MST) and Rapid Per-VLAN Spanning Tree Plus ( Rapid PVST+) depends on the number of VLANs requested by the
design and how many of these VLANs need to be on any individual links (logical interfaces count).
(MST) and Rapid Per-VLAN Spanning Tree Plus ( Rapid PVST+) depends on the number of VLANs requested by the
design and how many of these VLANs need to be on any individual links (logical interfaces count).
Chapter 4 covers the design choice of MST versus Rapid PVST+ in a vPC-based data center.