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MPLS Based VPNs and MP-BGP

posted in Cisco Networking, Technical
by on September 10th, 2009 tags: , , ,

Welcome to Multi Protocol Label Switching Virtual Private Networks with Multi Protocol Border Gateway Protocol. This article is designed for those who have only briefly seen MPLS and those that may already be working with an MPLS provider network and wish to have a peek into what is actually going on within the provider network.

Keep in mind however that MPLS networks almost by their definition can be deployed in a variety of ways and that is reflected by the way it is presented at the Customer Edge. Here it is presented as a L3 routed VPN.

I have put together a few videos that takes you from the very start of setting up your own MPLS lab. From dragging the router icons into the GNS workspace all the way through to testing connectivity from the customers perspective.

This is a diagram of the lab we will be setting up:

MP-BGP Diagram

Part 1 – Basic Setup


1) Each Router is given a loopback address of the router number as its octets with a 32bit mask.
2) Remember to define the loopback before setting up configuring “mpls ip” on any interface.
3) Test connectivity as you go.

Part 2 – Setting up the IGP (OSPF) and MP-BGP on the Provider Routers


1) Although we had set-up MPLS with the “mpls ip” on each interface in the previous video, LDP does not actually bring up the adjacencies until we bring the loopback address into OSPF.
2) Check that the OSPF and LDP adjacencies comes up as you move from router to router.
3) As the provider network is not a full mesh we are using route reflectors in the core network to move the customers routes around.
4) The command “no bgp default ipv4-unicast” disables Ipv4 unicast session establishment.
i.e. BGP will not peer unless you “activate” it.

Part 3 – Setting up the Provider Edge and the Customer Edge


1) It is function of the Provider Edge routers to bring in the Customers BGP routes from the VRF into the BGP VPN.
2) Route Distinguishers “rd 1:1” are used to distinguish between two different customers that use the same prefix. e.g. Customer 1 and Customer 2 both using

Part 4 – Testing The Configuration



MPLS Configuration on Cisco IOS Software
MPLS and VPN Architectures (Vol 1)
Configuring MPLS Layer 3 VPNs

Check out roggy’s blog for more Cisco technical articles.


A thread has been created on the site forum specifically for commenting on this blog post.

6 Responses to “MPLS Based VPNs and MP-BGP”

  1. Vito_Corleone


  2. ronal120

    Hi I have a question about the GSN3.

    that has the features PC used during the practice??

  3. roggy

    I think you mean the spec of the pc?
    Its a windows 7 box with a 3.8ghz quad core and 4gb of ram, however you can get away with alot less once idle pc is configured correctly. Remember for idlepc to work you have to be in exec mode.

  4. ronal120


    PD:sorry, I do not speak English

  5. Chinese Buffet

    Good video Richard!