Routing and Switching Topics with Narbik Kocharians: Lesson 2: Applying the VRF to Interfaces


    Lesson 2: Applying the VRF to Interfaces

    In Lesson two, Narbik Kocharians begins by answering a few attendee questions about what was covered in Lesson 1. Jumping back into the session, Narbik explains that once the VRFs are configured, they have to be applied to interfaces or sub-interfaces. The process of assigning VRFs to interfaces is similar to how VLANS are configured by assigning them to each interface. When the VRF is assigned to a given interface, VRF sees and removes an IP address for an interface and provides a consol message. In a CCIE lab, Narbik explains that removing the IP address can confuse you. He recommends to go to the PE router, do a show run interface command, then go to the interface configuration mode, remove the IP address.


    Once the VRFs are configured, Narbik then turns his attention towards what the customer routes should be. Using a route distinguisher, or a 64 bit value that is attached to the customer routes to make the customer routes unique, Narbik has PBGP take the routes from one PE router to another. This allows us to distinguish one customer's routes from another. Narbik then configures this onto the VRF. ures this onto the VRFs.


    Narbik then takes you through the entire process of what he has built so far. He begins with the customer sending an update. The update is received through the interface belonging to the VRF. He then ensures the matching VRF, and attaches the value to the customer route. Together with the VRF ID and the IP address from the customer route, Narbik produces a 96-bit addressing for VPNv4. Then, by configuring an address family VPNv4, Narbik explains that the second customer router has to be configured similarly, but inversely. When the second customer router receives the VPNv4 route, it removes the route distinguisher to create an IP address.


    The missing component in this configuration, Narbik explains, is a route target, or a BGP extended community that identifies which routes should be exported out of a given VRF into PBGP, and which routes should be imported from MPBGP to a given VRF. He then goes through the process of configuring the route targets, which he attaches to the VPNv4. He then proceeds to do the same thing on the other customer router.


    Lesson 1: Introduction to MPLS and Layer 3 VPNs

    Lesson 2: Applying the VRF to Interfaces

    Lesson 3: Redistribution Methods

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