Nexus 5k & 2k when using FabricPath at the 5k

[william.briere]

Hi,

When you're using FabricPath between 5k's and have dual homed fex from the 2k's to the 5k's do the 2k's use both links to each 5k's in an active/active state like they do if i created vPC links?

Thanks in advance.

[Reza Sharifi]

Hi,

Correct, both links from the 2k go onto a vpc and are forwarding.

For FEXs, the vpc number starts from 101.

HTH

[william.briere]

So I undertsand what you're are saying, you are telling me that I still need to create a vPC between my 2248's and the 5548's using the 10g-fex sfp's. Right?

[Reza Sharifi · Accepted solution]

That is correct.  You need to put the links from each 2248 in a vpc. Here is sample config from one 5k.  You would need the same config on the other 5k.  These FEXs are also 2248.

interface port-channel101

  switchport mode fex-fabric

  fex associate 101

  vpc 101

interface port-channel102

  switchport mode fex-fabric

  fex associate 102

  vpc 102

interface Ethernet1/5

  switchport mode fex-fabric

  fex associate 101

  channel-group 101

interface Ethernet1/6

  switchport mode fex-fabric

  fex associate 102

  channel-group 102

HTH

[william.briere]

I guess my question deepens to this. Is FabricPath an alternative to vPC, or something used "with" vPC? I assumed that when I turned ports that connected 5k's together to use switchport mode FabricPath it then made the need for vPC unnecessary.

[william.briere]

I guess my question deepens to this. Is FabricPath an alternative to vPC, or something used "with" vPC? I assumed that when I turned ports that connected 5k's together to use switchport mode FabricPath it then made the need for vPC unnecessary.

[Reza Sharifi · Accepted solution]

I have not deployed fabricpath, but I guess it depends on your design and the amount of bandwidth you need.  If you want one big layer-2 domain with hundreds or thousands of servers then fabticpath may be the way to go.

Cisco FabricPath Use Cases

The  value proposition of Cisco FabricPath - to create simple, scalable, and  efficient Layer 2 domains - is applicable to many network scenarios.  Since Cisco FabricPath began shipping in October 2010, Cisco customers  have been implementing a wide variety of network designs, from full-mesh  to ring topologies. Some of these use cases are presented in this  section.

Cisco FabricPath in a Typical Data Center Design

Cisco  FabricPath is often associated with scalability and performance.  However, today's data centers are generally built around small Layer 2  blocks, called pods. An example of such a network is data center A,  represented in Figure 3. Within a pod, switching is handled by Cisco  NX-OS vPC technology. vPC provides an active-active environment that  does not depend on Spanning Tree Protocol and that converges quickly in  the event of failure. Because vPC seems sufficient at this scale, it is  important to note some other aspects of Cisco FabricPath that makes it  attractive in this scenario:

•  Cisco FabricPath is simple to configure and to manage. There is no need  to identify a pair of peers or configure PortChannels. All the devices  in the fabric have the same role and same minimal configuration.

•  Cisco FabricPath is flexible and does not require a particular  topology. Even if the network is currently cabled for the classic  triangle vPC topology, Cisco FabricPath can accommodate any design that  might be needed in the future.

•  Cisco FabricPath does not use or even extend Spanning Tree Protocol.  Even a partial introduction of Cisco FabricPath has a beneficial effect  on the network because it segments the span of Spanning Tree Protocol.  Because it is an optimization of Classical Ethernet, vPC still requires  Spanning Tree Protocol on top of it to address certain scenarios.

•  Cisco FabricPath can be extended easily without degrading operations.  Adding a switch or a link in a Cisco FabricPath fabric does not result  in a single frame loss. It is thus possible to start with a small  network and extend it gradually, as needed.

More info:

http://www.cisco.com/en/US/prod/collateral/switches/ps9441/ps9402/white_paper_c11-605488.html

HTH