Why do Cisco MPLS TE tunnels require a link-state routing protocol?
Why do Cisco MPLS TE tunnels require a link-state routing protocol?
Cisco MPLS TE tunnels require a link-state routing protocol because the tunnel endpoints use the link-state database to evaluate the entire topology and determine the best path. Link-state protocols provide comprehensive information about the network's topology, which is essential for determining optimal routing paths for traffic engineering. This capability is crucial for the efficient implementation of MPLS TE tunnels, as it allows for better path calculation and network resource management.
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Information distribution is a link state protocol, such as Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS), which is necessary to discover the topology. These protocols have been enhanced to carry additional information related to TE, such as bandwidth available and other related parameters. IS-IS uses new Type Length Values (TLVs) and OSPF uses Type 10 (Opaque) Link State Advertisements (LSAs) for this purpose. Other IGPs cannot be used to implement MPLS TE. https://community.cisco.com/t5/networking-knowledge-base/how-mpls-traffic-engineering-works/ta-p/3128593