It seems appropriate to write a FFF post about Virtual Extensible LAN (VXLAN) now since VXLAN is the new hotness in the data center these days. With VMware's NSX using VLXAN (among other overlays) as a core part of its overall solution and the recent announcement of Cisco's Application Centric Infrastructure (ACI) and the accompanying Nexus 9000 switch, both of which leverage VXLAN for delivering a network fabric, it seems inevitable that network engineers will have to use and understand VXLAN in the not too distant future.

As usual, this post is not meant to be an introduction to the technology; I assume you have at least a passing familiarity with VXLAN. Instead, I will jump right into 5 operational/technical/functional aspects of the protocol.

For more information on VXLAN, check out the draft at the IETF.

We're halfway through 2013 and we have our second new member of the Nexus family of switches for the year: the Nexus 7700. Here are the highlights:

• Modular, chassis-based system
  • 18 slot (16 IO modules) and 10 slot (8 IO modules)
• True front-to-back airflow
• New fabric modules
  • (6) fabric modules (maximum) per chassis
  • 220G per slot per fabric module
  • 1.32Tbps per IO module slot
• Supports F2E and newly announced F3 IO modules

Here's a topic that comes up more and more now that FabricPath is getting more exposure and people are getting more familiar with the technology: Can FabricPath be used to interconnecting data centers?

FabricPath has some characteristics that make it appealing for DCI. Namely, it extends Layer 2 domains while maintaining Layer 3 — ie, routing — semantics. End host MAC addresses are learned via a control plane, FP frames contain a Time To Live (TTL) field which purge looping packets from the network, and there are no such thing as blocked links — all links are forwarding and Equal Cost Multi-Pathing (ECMP) is used within the fabric. In addition, since FabricPath does not mandate a particular physical network topology, it can be used in spine/leaf architectures within the data center or point-to-point connections between data centers.

Sounds great. Now what are the caveats?

There's a new Nexus in the family, the Nexus 6000. Here are the highlights.

Do you ever find yourself in a conversation with someone where you attempt to explain a concept in detail and you realize that you don't know that concept at the level of detail that you thought you did? That happened to me recently. I thought I had a better handle on TRILL and FabricPath than I really did. Since I retain things far better when I write them down, I'm going to blog the differences between TRILL and FabricPath when it comes to address learning and what role the control plane plays in building the network topology

FabricPath is Cisco's proprietary, TRILL-based technology for encapsulating Ethernet frames across a routed network. Its goal is to combine the best aspects of a Layer 2 network with the best aspects of a Layer 3 network.

• Layer 2 plug and play characteristics
• Layer 2 adjacency between devices
• Layer 3 routing and path selection
• Layer 3 scalability
• Layer 3 fast convergence
• Layer 3 Time To Live field to drop looping packets
• Layer 3 failure domain isolation

An article on FabricPath could go into a lot of detail and be many pages long but I'm going to concentrate on five facts that I found particularly interesting as I've learned more about FabricPath.