Wednesday, April 11, 2012

PE Role in MPLS


  • PE router:
    • An LSR that shares a link with at least one Customer Edge router, 
    • edge of MPLS VPN, IBGP & VRF tables
  • PE & P routers can together label switch packets from the ingress PE to the egress PE router.
  • PE .have several other duties:
    • Learn customer routes
    • & keep track of which routes belong to which customer.
    • Exchange routes with connected CE routers from various customers.
    • To keep the track of the possibly overlapping prefixes.
  • PE routers do not put the routers in normal IP routing table
    • instead , PEs store routes in separate per-customer routing tables, called VRFs
  • To exchange these customer routes with other PEs use IBGP.
    • never advertise these routes to P routers.
  • PEs advertise Route Targets in BGP updates as BGP Extended Community Path Attributes (PAs)