Wednesday, April 11, 2012

MPLS Route Targets


  • MPLS uses Route Targets to determine in which VRFs, a PE places IBGP-learned routes.
  • It is 64-bit extended BGP community.
  • It is attached to a VPNv4 BGP route to indicate its VPN membership
  • Any number of RTs attached to a single route up to the BGP update packet size of 4096 bits.
  • Export RTs
    • Attached to a route when it is converted into a VPN4 route.
    • Identify the VPN membership by associating routes to a VRF
  • Import RTs
    • Used to select VPNv4 routes for insertion into matching VRF tables.
    • On the receiving PE router, a route is imported into a vrf only if at least one RT attached to the route matches at least one import RT configured in that VRF(route map condition must be met if configured).
  • An import or export map allows route control on a per-route basis.

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