MPLS VPN components:

• VRF:
• Allows multiple tables on the same routers.
• Each vrf have separate:
• RIB
• FIB
• LFIB
• VRF is locally significant to router.
• The traffic entered into the VRF enabled interfaces is belong to that vrf.
• Only one vrf can be assigned to each VRF but one VRF contain any number of interfaces.
• Route Distinguishers:
• VPN routes are propagated across a MPLS VPN network by MP-iGMP
• To make these routes unique RDs are used.
• RD is locally significant & globally relevance.
•  Routing Timers:
• Export RTs
• Attached to a route when it is converted into VPNv4 route
• Import RTs
• RTs are used to select VPNv4 routes to insert into matching VRF tables.
• The matched route is only added to vrf table only when RT is attached to the matched route on PE router.
• Routing Protocols:
• IGP 1: 
• Between CEs & PEs
• used to advertise routes in the VRF routing table
• IGP will be any of the IGP protocol/static route/ebgp
• IGP 2:
• This is core MPLS IGP
• Support the LDP
• LDP:
• Between MPLS enabled routers
• MP-BGP:
• Only between PE routers
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• 2 Types of labels in label stack:
• Outer/Top/LDP label:
• Used for switching the label in the mpls core network
• Inner/Bottom/VPN label:
• Used for switching towards the egress pe router & identify the outgoing interface.
• MPLS VPN Label Operations:
• Every PE router assign a VPN label to every local VRF route.
• This vrf routes with VPN labels are advertised to remaining PE routers in MP-iBGP updates.
• After converging on PE routers,
• For every non-local VRF route will be labeled with VPN/inner label along with inner/LDP label for every BGP next-hop.
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