Tuesday, April 10, 2012

MPLS Tunnel


  • MPLS tunnels are known as LSP(label switching path)
  • MPLS tunnels(LSP) are unidirectional.
  • MPLS main advantages No need to know about source & destination IP address.
  • No need to run BGP in MPLS core. 
  • Router outside the sp network can be label switched based on the BGP next-hop
  • MPLS tunnel label, transports MPLS labeled VPN packets b/n Provider Edge routers along the LSP.
  • MPLS VPN label remains the same between PEs.
  • MPLS tunneling is most widely supported, particularly for manually configured, point to point tunnels.
  • MPLS tunnel problems:
    • BGP next-hop values must be loopback interface of remote PE.
    •  BGP next-hop determine what label value should be used.
    • Incorrect next-hop vlalue can result in traffic black hole in MPLS network
      • label is PHPed one shop to soon
  • MPLS tunnels are similar to Frame-Relay or ATM PVCs.
    • Frame-Relay packets are switched based on the DLCI value found in the header.
    • This DLCI value is purely local
    • These DLCI value on packet header is rewritten every time the packet switched out.
    • similar principle is employed in MPLS.
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