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. 

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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). 

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.