Skip navigation
Cisco Learning Home > CCNP R&S Study Group > Discussions
1682 Views 7 Replies Latest reply: Aug 27, 2012 11:29 AM by d.serra RSS

Currently Being Moderated

What is Overlay Network?

Feb 13, 2012 11:07 PM

Praveen Rai 17 posts since
Feb 13, 2012

Hi team,


today while  reading MPLS i got to know this term m confused about whats all about it after reading i found overlay network is somewhat like Frame relay in which we create VC to connect customer L3 IP to L2 services and isolate it from other so pls correct me m right or it is something else pls make this clear to me


whats the advantage of it..............................if somebody clear it with visual it would give morwe sense....................

  • rmhango 555 posts since
    Aug 12, 2008
    Currently Being Moderated
    1. Feb 14, 2012 3:46 AM (in response to Praveen Rai)
    Re: What is Overlay Network?

    Don't allow the term to confuse you, Overlay Networks are nothing new and have evolved over time, its just a matter of understanding the operation, today MPLS is the most prominent and the advantages are clear!  

  • Anthony Sequeira, CCIE,VCP 1,011 posts since
    Nov 9, 2008
    Currently Being Moderated
    2. Feb 14, 2012 5:05 AM (in response to Praveen Rai)
    Re: What is Overlay Network?

    There have been two primary VPN models that have been used by Service Providers:


    • The overlay model - where the service provider provides emulated leased lines to the customer. The overlay model typically uses the virtual circuits of a Frame Relay or ATM service. The overlay model has advantages such as permitting the duplication of addresses and the isolation of the control and security planes.
    • The peer-to-peer model - where the service provider and the customer exchange Layer 3 routing information and the provider relays the data between the customer sites on the optimum path between the sites. Layer 3 MPLS VPNs permit the creation of a peer-to-peer model with many of the advantages of the overlay model, such as the duplication of addresses.


    Anthony Sequeira

    Twitter: @compsolv


  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,395 posts since
    Oct 7, 2008
    Currently Being Moderated
    3. Feb 14, 2012 10:31 AM (in response to Praveen Rai)
    Re: What is Overlay Network?

    When one type of network runs on top of another network, that's an overlay.  As noted, MPLS VPNs are a primary example of that, because what a customer views as "the network" is a very limited scope of the REAL network making all that possible.


    So one is overlaid on top of the other.





  • chrisjoms 378 posts since
    Jul 22, 2010
    Currently Being Moderated
    Re: What is Overlay Network?

    Hi Scott, really make sense your explanation for the term overlay. I was reading your response on the other thread regarding SONET. 


    And you commented on that link that MPLS is overlay,  then i found another post of yours that clears the dark clouds of my understanding for the term overlay.


    Thank you so much.


    I just hope one day, when CISCO wants you to write a book that you will do the same, stick to the point and clear as a crystal water the explanation.


    Because some of the author for Cisco book, they will drive you around in circles before you get the idea. when in fact it is just a very small matter.


    anyway i think that's how marketing strategy works.


    to the original poster, don't really  mean to hijack this post.


    But can't find a way to thank Scott except to do this. Thanks again Sir Scott.

  • Scott Morris - CCDE/4xCCIE/2xJNCIE 8,395 posts since
    Oct 7, 2008
    Currently Being Moderated
    5. Feb 22, 2012 5:24 AM (in response to chrisjoms)
    Re: What is Overlay Network?

    heheheh...  I'm discovering the difficulty in that is it takes a lot of time and energy to write a book!  But yes, what I'm working on, I'm trying to make crystal clear as well as fun and simple to read! 


    Glad to help!



  • klaus 124 posts since
    Feb 1, 2012
    Currently Being Moderated
    Re: What is Overlay Network?

    Just curious who will win the battle, peer to peer or overlay networks interns of usage?

  • d.serra 7 posts since
    Nov 12, 2009
    Currently Being Moderated
    Re: What is Overlay Network? much as I respect Scott and everything he had achieved and contributed to so many CCIEs, I have to respectfully disagree with MPLS being an ‘overlay network’ and agree with Anthony Sequeria.  It is all about who you peer routing with.  Frame-Relay is an overlay network because the provider does not participate in customer routing.  MPLS is a ‘peer-to-peer’ model network because the provider Does participate in customer routing. 


More Like This

  • Retrieving data ...

Bookmarked By (0)