Which statement about the Cisco MPLS TE forwarding adjacency feature is true?
Which statement about the Cisco MPLS TE forwarding adjacency feature is true?
The Cisco MPLS TE forwarding adjacency feature allows an MPLS Traffic Engineering tunnel to be advertised as a link in the Interior Gateway Protocol (IGP) routing tables. This enables the MPLS core network to facilitate traffic engineering by providing the capability to include MPLS TE tunnels as part of the IGP’s topology.
B. Is correct. "When the MPLS Traffic Engineering Forwarding Adjacency feature is enabled on a TE tunnel, the link is advertised in the IGP network as a type, length, value (TLV) 22 object without any TE sub-TLV." ...THEN, "You must configure MPLS TE forwarding adjacency tunnels bidirectionally" See section: "Restrictions for MPLS Traffic Engineering Forwarding Adjacency": https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_te_path_setup/configuration/xe-16-6/mp-te-path-setup-xe-16-6-book.pdf
Link is broken, her is the new one: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_te_path_setup/configuration/xe-16-6/mp-te-path-setup-xe-16-6-book/mpls-traffic-engineering-forwarding-adjacency.pdf
B is correct, I worked with this technology.
From Cisco training (no link): Fast Reroute (FRR) is a mechanism for protecting a Cisco MPLS TE LSP from link and node failures by locally repairing the LSP at the point of failure. The FRR mechanism allows data to continue to flow while the headend router attempts to establish a new end-to-end LSP that bypasses the failure. FRR locally repairs any protected LSPs by rerouting them over backup tunnels that bypass failed links or nodes. The headend is notified of the failure through the IGP and through RSVP. The headend then attempts to establish a new LSP that bypasses the failure (LSP rerouting). The important fact to remember is that when using fast reroute, the protection kicks in as soon as the protected interface fails, which in turn forces the head end to recalculate a new path for the dynamic Cisco MPLS TE tunnel. In that brief period of time, between when the head-end of tunnel 1 realizes that the path is invalid and when the new path is calculated, the fast reroute happens via a predefined tunnel. Fast Reroute prevents end to end traffic loss during the path recalculation.
Sorry, ignore the above!
Using forwarding adjacency, which allows the tunnel to be announced via OSPF or IS-IS as a point-to-point link to other routers. To be used for data forwarding, such a traffic tunnel has to be set up bidirectionally.