When you go to set up a server in the data center it usually requires planning and coordination between independent teams such as the network, server, storage, and application teams.   Depending on the size of the company and how the internal organization is set up this can become a huge hassle and take weeks to accomplish the simplest items.  Also, when you go to move a server to a different location, usually this means changing its IP address.  And as we all know changing an IP address on a server is usually not simple or fun (Huge understatement).  It can affect applications that point to it, you might need to change rules on a firewall, etc.  Cisco FabricPath gives you the foundation for building highly scalable datacenter network and moving server locations with none of these issues.  It does this by making the network look like a single virtual switch when looking from the outside in.

So how does it do this?  When a server or an end user sends an Ethernet frame, FabricPath takes the frame and encapsulates with a FabircPath header which consists of the source and destination addresses.  The source address being the address of the switch which received the frame, and the destination address being the switch to which the frame is going to.  When the frame arrives at the destination switch it is de-encapsulated and delivered to the destination host.  Here is a graphic from Cisco that shows the process.

<a href="http://egroup.jasonmangone.com/?attachment_id=6379" rel="attachment wp-att-6379"><img class="alignnone size-medium wp-image-6379" src="http://egroup.jasonmangone.com/wp-content/uploads/2012/03/white_paper_c11-605488-1-300x117.jpg" alt="" width="300" height="117" /></a>

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So what are the benefits to implementing FabricPath?  Well besides being just awesome and fun to implement, Cisco has given us the following:

– Cisco FabricPath is extremely simple to configure. In fact, the only necessary configuration consists of distinguishing the core ports, which link the switches, from the edge ports, where end devices are attached. There is no need to tune any parameter to get an optimal configuration, and switch addresses are assigned automatically.

– A single control protocol is used for unicast forwarding, multicast forwarding, and VLAN pruning. The Cisco FabricPath solution requires less combined configuration than an equivalent Spanning Tree Protocol-based network, further reducing the overall management cost.

– Static network designs make some assumptions about traffic patterns and the locations of servers and services. If those assumptions are incorrect, a situation that often happens after a while, complex redesign may be necessary. A network based on Cisco FabricPath can be modified as needed in a nondisruptive manner for the end stations.

– The capabilities of Cisco FabricPath troubleshooting tools surpass those of the tools currently available in the IP world. The ping and traceroute features now offered at Layer 2 can measure latency and test a particular path among the multiple equal-cost paths to a destination within the fabric.

– A device that does not support Cisco FabricPath can be attached redundantly to two separate Cisco FabricPath bridges with enhanced virtual PortChannel (vPC+) technology, providing an easy migration path.

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These are huge benefits.  You don’t have to tune the parameters, you can modify the FabricPath configuration with no downtime, and the modified ping command.  As a network admin these are all things we have wished we have had for many years now.

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So when would you use FabricPath?  Pretty much in any datacenter design that you wanted to build that is easy to configure, highly scalable, and easy to manage.  Data centers today are typically built in small layer 2 blocks.  In a Cisco NX-OS environment today all switching is usually handled by vPC.   While this removes spanning-tree seems sufficient here are some reasons from Cisco and why FabricPath is so much better.

• 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.

Here is a graphic from Cisco showing the two different datacenters.

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I hope this has given an overview on FabricPath and the benefits to using it.  Check back soon for my next port on FabricPath.  FabricPath part 2:  How to implement FabricPath.