Руководство По Проектированию для Cisco Cisco Nexus 5010 Switch
Design Guide
© 2010 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information.
Page 3 of 38
Virtual PortChannel Technology
Virtual PortChannels (vPCs) allow links that are physically connected to two different Cisco
®
switches to appear to a
third downstream device to be coming from a single device and as part of a single PortChannel. 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
®
7000 and 5000 Series platforms (with or without Cisco Nexus 2000 Series Fabric
Extenders).
vPC Basics
The fundamental concepts of vPC are described at
vPCs consist of two vPC peer switches connected by a peer link. Of the vPC peers, one is primary and one is
secondary. The system formed by the switches is referred to as a vPC domain.
Following is a list of some possible Cisco Nexus vPC topologies:
●
vPC on the Cisco Nexus 7000 Series (topology A): This topology consists of 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 hosts connected with virtual PortChannels to each Cisco Nexus 7000
Series Switch.
●
vPC on Cisco Nexus 5000 Series (topology B): This topology consists of switches dual-connected to the Cisco
Nexus 5000 Series with a switch PortChannel with 10 Gigabit Ethernet links, with one or more links to each
Cisco Nexus 5000 Series Switch. Like topology A, topology B can consist of servers connected to each Cisco
Nexus 5000 Series Switch via virtual PortChannels.
●
vPC on the Cisco Nexus 5000 Series with a Cisco Nexus 2000 Series 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 eight 10 Gigabit Ethernet links (depending on the fabric extender model) to
a single Cisco Nexus 5000 Series Switch, and of Gigabit Ethernet or 10 Gigabit Ethernet-connected servers
that form virtual PortChannels to the fabric extender devices. Note that each fabric extender connects to a
single Cisco Nexus 5000 Series Switch and not to both, and that the virtual PortChannel can be formed only
by connecting the 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.
●
Dual-homing of the Cisco Nexus 2000 Series Fabric Extender (topology D): This topology is also called Cisco
Nexus 2000 Series Fabric Extender (FEX for brief) Active/Active. In this topology each FEX is connected to
each Cisco Nexus 5000 Series device with a virtual PortChannel. 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.
Note: Topologies B, C, and D are not mutually exclusive. You can have an architecture that uses these three
topologies concurrently.
topologies concurrently.