Category: Tags

SD-WAN

Software-Defined WAN (SD-WAN) is the second “software-defined” marketing attempt (after the original SDN) to dress a conglomerate of old technologies into shiny new clothes. Even Wikipedia article promotes some of the usual software-defined hype, quoting Network World claim that:

SD-WAN simplifies the management and operation of a WAN by decoupling the networking hardware from its control mechanism. This concept is similar to how software-defined networking implements virtualization technology to improve data center management and operation.

Is It Real?

Want to know how real those claims are? Start the journey with this series of myth-busting blog posts:

Does SD-WAN make sense? Sure:

Need More Details?

I covered the basics of SD-WAN in Choose the Optimal VPN Service and SDN Use Cases webinars.

Pradosh Mohapatra described the basics of SD-WAN and its typical components and architectures:

Want to know more about Cisco’s SD-WAN solution (formerly known as Viptela)? Enjoy David Peñaloza Seijas’ deep dive into its architecture and implementation details:

Real-Life SD-WAN

SD-WAN sounds great, but does it work as expected? Maybe not:

Is it secure? Some products seem to be nothing more than a bunch of open-source component glued together with clueless Python code:

Some service providers want to use SD-WAN to offer managed services. Not surprisingly, some people1 don’t find that a good idea:

Then there are some technical details vendors love to gloss over:

Does it work within a public cloud? Yeah, sort of… with a few challenges:

Want Even More?

Love marketing-related rants? Here are a few:

Last, but definitely not least, you might enjoy these (more esoteric) solutions:

Blog Posts I Forgot to Categorize

  1. Including those working for said service providers or their customers ↩︎

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EIGRP

EIGRP was the best choice for an interior gateway protocol in late 1990s – it was fast, efficient, and easy to deploy. OSPF and IS-IS implementations improved in the intervening 30 years, slowly turning EIGRP into a forgotten technology.

On a more serious note, I wouldn’t deploy EIGRP in new network designs for compatibility reasons (no major networking vendor apart from Cisco implemented it), and I’d use BGP in designs where a single router has to deal with hundreds of adjacent routers (the only scenario where EIGRP still outshines OSPF and IS-IS).

While the ultimate sources of EIGRP wisdom remain the EIGRP Network Design Solutions Cisco Press book and RFC 7868, you might want to read these articles and blog posts describing EIGRP implementation details and deployment guidelines.

The Basics

Implementation Details

EIGRP Deployment Scenarios

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DMVPN

DMVPN is an old1 Cisco-proprietary technology that combines NHRP, IPsec, IKEv2 and multipoint GRE tunnels to build dynamically-provisioned multi-access VPNs.

The easiest way to master DMVPN is to watch the ipSpace.net DMVPN webinars, and every now and then someone still finds them somewhat useful:

I also wrote dozens of DMVPN-related blog posts. Hope you’ll enjoy them!

The Basics

DMVPN always relies on a hub-and-spoke topology, but enables direct communication between spokes (Phase-2 DMVPN) and simplified routing with NHRP redirects (Phase-3 DMVPN).

Routing Protocols in DMVPN Networks

Routing protocols face significant challenges in DMVPN networks due to very large number of directly-connected neighbors, with EIGRP faring better than OSPF, and BGP being the only viable solution in deployments with a very large hub-to-spoke ratio.

Typical DMVPN Designs

DMVPN Deployment Guidelines

Integration with Other Network Technologies

DMVPN Alternatives

Quirks and Implementation Details

I wrote numerous blog posts documenting DMVPN quirks while preparing the materials for the DMVPN webinars. Most of these blog posts were written in early 2010s and might no longer be relevant.

  1. As in: created around 2010. For more details, listen to the History of DMVPN with Mike Sullenberger. ↩︎

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