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Dynamic Multipoint VPN (DMVPN) Setup.

Since DMVPN has been added to the CCIE v5 BluePrint ( I figured that now was just as good of a time as any to write this blog.

DMVPN stands for Dynamic Multipoint VPN and it is an effective solution for dynamic secure overlay networks.

DMVPN is combination of the following technologies:

  • Multipoint GRE (mGRE)
  • Next-Hop Resolution Protocol (NHRP)
  • Dynamic Routing Protocol (EIGRP, RIP, OSPF, BGP)
  • Dynamic IPsec encryption
  • Cisco Express Forwarding (CEF)

Topology that we will be starting with:

Colby's Blog Image 1

First thing will be to complete the base configurations on R1, R2 & R3. This will consist of configuring the IP addresses on the above interfaces and setting up the routing protocol to distribute the routes. In this case we will use EIGRP 123. Read More »

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Cisco Opens Up EIGRP

What’s new and exciting with EIGRP (Enhanced Interior Gateway Routing Protocol)? Actually, lots…  First a bit a background on EIGRP.

EIGRP is an advanced distance vector routing protocol used extensively by enterprise customers.  It is very popular because it is simple to deploy and support. Some major attributes are:

  • EIGRP does not mandate many network design requirements and is therefore perceived as “forgiving” and “flexible”.  For example, EIGRP does not require support for multiple routing sub-domains or Areas.
  • While route summarization is a recommended best practice to minimize route table size, it is optional with EIGRP.
  • EIGRP can scale to support thousands of routers in a Hub and Spoke configuration.  The Hub and Spoke design is especially popular in WAN networks.

For additional information on EIGRP, please click here.  There is also a great BLOG that compares EIGRP and OSPF that I think you will find informative and is posted here.

While EIGRP has a large customer following, some customers have hesitated because of concerns of EIGRP being “proprietary”, which would prevent them from multi-vendor network support.  In some cases this has caused customers to design their networks to limit usage of EIGRP, even though they would like to deploy it ubiquitously.  One result has been non-optimal network design and traffic flow, resulting from multiple IGP (Interior Gateway Protocol) redistribution points.

That brings me back to what is new and exciting with EIGRP. Read More »

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A week in my life at Cisco Live London

February 1, 2013 at 4:23 am PST

It is not often you get a peek in the behind scenes of the Cisco Employees who put their personal lives on hold to support a major event like Cisco Live.  I am very sure this blog will not do justice to sharing one person’s perspective, but lets give it a try shall we?

Read More »

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EIGRP vs OSPF – Take 2

September 13, 2012 at 8:01 am PST

First a bit of disclosure.  I have worked for Cisco over 15 years, much of that time as the lead developer for EIGRP. I think I understand its strengths and weakness’ very well, and have spent a great deal of energy minimizing them.

I often find comparing protocols similar to the old “tab vs spaces” or “emacs vs vi” wars.  There are valid reasons to choose one over the other and in the grand scheme of things it comes down to a wash; often preference or ‘religion’.  EIGRP seems to victim to this .  I mean where are the “ISIS vs OSPF” debates?  With EIGRP, network engineers that love it – love it. Those that don’t, well they don’t. Arguing its merits often results in an equally long list of “yea but” demerits.

For example, most everyone would agree eigrp is “simple to deploy”, but detractors would argue that simplicity leads to sloppy designs and only though complexity can we force network engineers to “do their job” and design the network properly. Read More »

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