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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Virtual PortChannel Technology
Virtual PortChannels (vPCs) allow links that are physically connected to two different Cisco
®
switches to
appear to a third downstream device as coming from a single device and as part of a single port channel.
The third device can be a switch, a server, or any other networking device that supports IEEE 802.3ad
PortChannels.
The third device can be a switch, a server, or any other networking device that supports IEEE 802.3ad
PortChannels.
Cisco NX-OS Software vPCs and Cisco Catalyst
®
Virtual Switching Systems (VSS) are similar technologies. For
Cisco EtherChannel
®
technology, the term multichassis EtherChannel (MCEC) refers to either technology
interchangeably.
vPC allows the creation of Layer 2 PortChannels that span two switches. At the time of this writing, vPC is
implemented on the Cisco Nexus
implemented on the Cisco Nexus
®
7000 and 5000 Series platforms (with or without the Cisco Nexus 2000 Series
Fabric Extenders).
vPC Topologies
Cisco Nexus vPC topologies can be categorized as follows:
●
vPC on the Cisco Nexus 7000 Series (topology A):
This topology comprises access layer switches dual-
homed to the Cisco Nexus 7000 Series with a switch PortChannel with Gigabit Ethernet or 10 Gigabit Ethernet
links. This topology can also consist of PortChannels with each host connected either with one or more links
to each Cisco Nexus 7000 Series.
links. This topology can also consist of PortChannels with each host connected either with one or more links
to each Cisco Nexus 7000 Series.
●
vPC on Cisco Nexus 5000 (topology B):
This topology comprises switches dual-connected to the Cisco
Nexus 5000 (switch PortChannels) with 10 Gigabit Ethernet links, either with one or more links to each Cisco
Nexus 5000 Series Switch.. Like topology A, topology B can consist of PortChannels where servers connect
at 10 Gigabit Ethernet with one or more ports to each Cisco Nexus 5000 Series.
Nexus 5000 Series Switch.. Like topology A, topology B can consist of PortChannels where servers connect
at 10 Gigabit Ethernet with one or more ports to each Cisco Nexus 5000 Series.
●
vPC on the Cisco Nexus 5000 Series with a Cisco Nexus 2000 Fabric Extender single-homed
(also
called straight-through mode) (topology C): This topology consists of a Cisco Nexus 2000 Series Fabric
Extender single-homed with one to four times 10 Gigabit Ethernet links to a single Cisco Nexus 5000 Series
Switch, and of Gigabit-Ethernet-connected servers that form PortChannels to the fabric extender devices. It is
important to notice that each fabric extender connects to a single Cisco Nexus 5000 Series Switch and not to
both, and that the PortChannel can be formed only by connecting each of the two server network interface
cards (NICs) to two fabric extenders, where fabric extender 1 depends on Cisco Nexus 5000 Series Switch 1
and fabric extender 2 depends on Cisco Nexus 5000 Series Switch 2. If both fabric extender 1 and fabric
extender 2 depend on switch 1 or both of them depend on switch 2, the PortChannel cannot be formed. In the
Cisco Nexus 2000 Series family, the Cisco Nexus 2148T has the restriction that only 2-Ports PortChannels
are supported.
Extender single-homed with one to four times 10 Gigabit Ethernet links to a single Cisco Nexus 5000 Series
Switch, and of Gigabit-Ethernet-connected servers that form PortChannels to the fabric extender devices. It is
important to notice that each fabric extender connects to a single Cisco Nexus 5000 Series Switch and not to
both, and that the PortChannel can be formed only by connecting each of the two server network interface
cards (NICs) to two fabric extenders, where fabric extender 1 depends on Cisco Nexus 5000 Series Switch 1
and fabric extender 2 depends on Cisco Nexus 5000 Series Switch 2. If both fabric extender 1 and fabric
extender 2 depend on switch 1 or both of them depend on switch 2, the PortChannel cannot be formed. In the
Cisco Nexus 2000 Series family, the Cisco Nexus 2148T has the restriction that only 2-Ports PortChannels
are supported.
●
Dual-homing of the Cisco Nexus 2000 Fabric Extender (topology D)
requires special considerations and
is described at the end of this chapter. With this topology the server cannot create a PortChannel split
between two fabric extenders. The servers can still be dual-homed with active/standby or active/active
transmit load balancing (TLB) teaming.
between two fabric extenders. The servers can still be dual-homed with active/standby or active/active
transmit load balancing (TLB) teaming.
Note: Topologies B, C, and D are not mutually exclusive. You can have an architecture that uses the three of
these topologies concurrently.
Figure 1 illustrates topologies A and B. Figure 2 illustrates topologies C and D.