Difference between VPC and Enhanced VPC

[Frankaviglia]

Hi all,

I can't figure out what is the difference between these two vPC modes.

I am interested in connecting a 2K to 2x Separate 7K (mod 7010) using vPC. Do we need any special requirements or this falls just within the normal vPC configurtion?

Many thanks,
Francesco

[Anuj Thapa]

Enahnced vPC is when FEX vPC to Southbound Host and Northbound to N5k.

Afaik ,Straight through vPc is supported today b/w Fex/N7k. ( may somebody can pitch in here)

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/release/notes/52_nx-os_release_note.html

Host vPC with FEX

The host vPC with FEX feature provides the ability to have a vPC from a host connected to two independent Cisco Nexus 2000 Series Fabric Extenders with a Cisco Nexus 7000 Series switch that acts as a parent switch to the FEX. The two Cisco Nexus 7000 Series switches that act as the parent switch form the vPC peers. The connectivity between the FEX and Cisco Nexus 7000 Series switch cannot be a vPC. It can be a link or a port channel.

Also check Slide 22 on https://communities.cisco.com/docs/DOC-35725

[Frankaviglia]

Aj, thank you for your comment.

Could you please show me where, in the Relese notes you attached, you can see that 7K supports FEX dual homing?

Also, in the second part of your post you say that the uplink from the 2K can not be a vPC? What is it supposed to be then?

Francesco

[Steve Fuller · Accepted solution]

Hi Franscesco,

Let me first give you some background on vPC and Enhanced vPC and then try and answer your specific questions.

Enhanced vPC is a method that allows the connection of FEX in an active-active manner using vPC between the FEX and upstream Nexus switch, and at the same time connection of a device to the FEX host interfaces with a vPC.

When the FEX was originally introduced it could only be connected to a single upstream switch in what's referred to as FEX "straight through" mode. In Cisco NX-OS 4.1(3)N1 the vPC feature was introduced that allowed the FEX to be connected in an "active-active" manner i.e., dual-homed.

The problem with FEX active-active at that time was that the servers connected to the host interfaces of the FEX could not be connected using port-channels i.e., link aggregation.

What Enhanced vPC does is to remove that limitation such that we can have FEX active-active with vPC to the upstream Nexus switch, and at the same time connect hosts with port-channels.

Each of the three models is shown in the attached diagram.

Could you please show me where, in the Relese notes you attached, you can see that 7K supports FEX dual homing?

In terms of support for Enhanced vPC, that is available from NX-OS 5.1(3)N1 on the Nexus 5500 series switches and on the Nexus 6000 series switches. There is no support for Enhanced vPC on the Nexus 7000 series switch currently.

When connecting FEX to Nexus 7000 switches, active-active is not supported today i.e., up to and including NX-OS 6.2. To see what topologies are supported in the Nexus 7000, take a look at the  document Nexus 7000 Fex Supported/Not Supported Topologies.

Also, in the second part of your post you say that the uplink from the 2K can not be a vPC? What is it supposed to be then?

As you're probably aware, virtual Port-Channel (vPC) is a method used in Cisco Nexus switches that make two switches appear to a downstream device as a single switch. When connecting a FEX to a single upstream Nexus 7000 series switch there is no vPC configuration required on the switch and the FEX is simply connected using a standard port-channel. On slide 22 of the Quick Start guide that AJ referenced you'll notice that there is no vpc command under the interface port-channel 199.

Regards

[Frankaviglia]

WOW, Great explanation - clear and mistakeproof with all the diagrams attached.

Makes perfcet sense and also the compatibility table.

Many thanks,

Francesco

[markus.radis]

I know its been quite some time now. But does anyone know if it is possible to connect Switches (eg. 2960s) via Port-Channel / VPC to the fex modules instead of clients?

[collinsjl]

No.  They do not participate in Spanning tree.  You can connect them to the 5K / 7K directly but not to the FEX

[ygazel]

That is a normal VPC, the N7K does not support multihoming a FEX, there is no special configuration for this, this is a regular VPC

HTH

Yamil