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Revisit Mobility Moments at Cisco Live Milan

Well, CiscoLive Milan 2015 is behind us…..but hopefully the energy and insights you took away from it stay with you – at least till next CiscoLive. Our attendees rated it as our most successful CiscoLive EMEAR ever……and having been to a few of them myself I’d happily agree!

I had the opportunity to speak with many attendees at the World of Solutions, both on the guided tours and also at the mobility demos. The overall impression I got from speaking with you is that you are as excited (and challenged) as we are about the dramatic changes going on in IT. The transformation of IT has moved from hype to reality – and many of you at CiscoLive are the ones being asked by your company to make these changes happen.

Now, whether you attended Live and missed a session – or you were not in Milan at all – you can still check out many of the keynotes and sessions on-line.

One of the highlights was the Enterprise Networking Trends keynote Read More »

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VXLAN/EVPN: Standards based Overlay with Control-Plane

Given the tremendous interest in VXLAN with MP-BGP based EVPN Control-Plane (short EVPN) at Cisco Live in Milan, I decided to write a “short” technology brief blog post on this topic.

VXLAN (IETF RFC7348) has been designed to solve specific problems faced with Classical Ethernet for a few decades now. By introducing an abstraction through encapsulation, VXLAN has become the de-facto standard overlay of choice in the industry. Chief among the advantages provided by VXLAN; extension of the todays limited VLAN space and the increase in the scalability provided for Layer-2 Domains.

Extended Namespace – The available VLAN space from the IEEE 802.1Q encapsulation perspective is limited to a 12-bit field, which provides 4096 VLANs or segments. By encapsulating the original Ethernet frame with a VXLAN header, the newly introduced addressing field offers 24-bits, thereby providing a much larger namespace with up to 16 Million Virtual Network Identifiers (VNIs) or segments.




While the VXLAN VNI allows unique identification of a large number of tenant segments which is especially useful in high-scale multi-tenant deployments, the problems and requirements of large Layer-2 Domains are not sufficiently addressed. However, significant improvements in the following areas have been achieved:

  • No dependency on Spanning-Tree protocol by leveraging Layer-3 routing protocols
  • Layer-3 routing with Equal Cost Multi-Path (ECMP) allows all available links to be used
  • Scalability, convergence, and resiliency of a Layer-3 network
  • Isolation of Broadcast and Failure Domains

IETF RFC7348 – VXLAN: A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks

Scalable Layer-2 Domains

The abstraction by using a VXLAN-like overlay does not inherently change the Flood & Learn behavior introduced by Ethernet. In typical deployments of VXLAN, BUM (Broadcast, Unicast, Multicast) traffic is forwarded via layer-3 multicast in the underlay that in turn aids in the learning process so that subsequent traffic need not be subjected to this “flood” semantic. A control-plane is required to minimize the flood behavior and proactively distribute End-Host information to participating entities (typically called Virtual Tunnel End Points aka VTEPs) in the same segment – learning.

Control-plane protocols are mostly employed in the layer-3 routing space where predominantly IP prefix information is exchanged. Over the past years, some of the well-known routing protocols have been extended to also learn and exchange Layer-2 MAC addresses. An early technology adoption with MAC addresses in a routing-protocol was Cisco’s OTV (Overlay Transport Virtualization), which employed IS-IS to significantly reduce flooding across Data Center Interconnects (DCI).

Multi-Protocol BGP (MP-BGP) introduced a new Network Layer Reachability Information (NLRI) to carry both, Layer-2 MAC and Layer-3 IP information at the same time. By having the combined set of MAC and IP information available for forwarding decisions, optimized routing and switching within a network becomes feasible and the need for flood to do learning get minimized or even eliminated. This extension that allows BGP to transport Layer-2 MAC and Layer-3 IP information is called EVPN – Ethernet Virtual Private Network.

EVPN is documented in the following IETF drafts

Integrated Route and Bridge (IRB) – VXLAN-EVPN offers significant advantages in Overlay networking by optimizing forwarding decision within the network based on Layer-2 MAC as well as Layer-3 IP information. The decision on forwarding via routing or switching can be done as close as possible to the End-Host, on any given Leaf/ToR (Top-of-Rack) Switch. The Leaf Switch provides the Distributed Anycast Gateway for routing, which acts completely stateless and does not require the exchange of protocol signalization for election or failover decision. All the reachability information available within the BGP control-plane is sufficient to provide the gateway service. The Distributed Anycast Gateway also provides integrated routing and bridging (IRB) decision at the Leaf Switch, which can be extended across a significant number of nodes. All the Leaf Switches host active default gateways for their respective configured subnets; the well known semantic of First Hop Routing Protocols (FHRP) with active/standby does not apply anymore.

Summary – The advantages provided by a VXLAN-EVPN solution are briefly summarized as follows:

  • Standards based Overlay (VXLAN) with Standards based Control-Plane (BGP)
  • Layer-2 MAC and Layer-3 IP information distribution by Control-Plane (BGP)
  • Forwarding decision based on Control-Plane (minimizes flooding)
  • Integrated Routing/Bridging (IRB) for Optimized Forwarding in the Overlay
  • Leverages Layer-3 ECMP – all links forwarding – in the Underlay
  • Significantly larger Name-Space in the Overlay (16M segments)
  • Integration of Physical and Virtual Networks with Hybrid Overlays
  • It facilitates Software-Defined-Networking (SDN)

Simply formulated, VXLAN-EVPN provides a standards-based Overlay that supports Segmentation, Host Mobility, and High Scale.

VXLAN-EVPN is available on Nexus 9300 (NX-OS 7.0) with  Nexus 7000/7700 (F3 linecards) to follow in the upcoming major release. Additional Data Center Switching platforms, like the Nexus 5600, will follow shortly after.

A detailed whitepaper on this topic is available on In addition, VXLAN-EVPN was featured during the following Cisco Live! Sessions.

Do you have appetite for more? Post a comment, tweet about it and have the conversation going … Thanks for reading and Happy Networking!

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Enterprise Networks Taking Center Stage at Cisco Live Milan

It is clear being an IT professional today is not easy, there are ever increasing demands on the network and on IT resources. Just look at some of the data out there:

Even in conversations with customers here at Cisco Live MilanCL Milan it is evident that IT is tasked to more with less, “I am told I need to be more agile.” Or, “Everyone is getting new Mobile Devices that are going to increase traffic.” Or “I needs to be more strategic to the business.”

It is clear that IT needs to rethink how they enable applications, secure the network and manage the infrastructure. But there is hope! Cisco is hard at work developing new solutions and products to help in meeting top of mind concerns. In recent January announcements, many being highlighted at Cisco Live Milan, Cisco has shown how new technology can help IT be more agile, support new demands and drive business impact. There have been a number of blogs talking about these announcements and below is where you can find out more about these exciting Cisco innovations.

Increasing IT Agility

  • Cisco ONE Delivers a More Valuable and Flexible way to Consume Cisco Software.
  • Cisco Meraki is delivering a global, enterprise-class, comprehensive Cloud-Managed IT solution

Supporting New Demands

Driving Business Impact

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Mobile in Milan – Cisco Live!

Whether you are among the 8,000 attendees participating at Cisco Live Milan in-person or among our many virtual attendees catching the live web broadcast, you’ll find lots to help you with your mobility-related projects.

Mobile in Milan

Read More »

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Cisco Live Europe 2015 – The ITM Millennial Team

CiscoLive! Milan 2015 kicks off on the 26th January and five Cisco IT graduates have been given the opportunity to attend the event as members of the IT Management (ITM) Program. On-site responsibilities will revolve around showcasing the impact & outcomes of Cisco IT to event attendees. We will also aim to reduce IT cost of delivering the ITM Program by assisting with operational activities, whilst gaining exposure to Cisco technologies, customers & partners.

Meet the team…  Read More »

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