Exam 350-501 topic 1 question 143 discussion

Correct answer is B. You can use the vrf keyword to select which virtual routing and forwarding (VRF) instance is to be protected if the device is configured with at least one virtual private network (VPN) VRF instance. You cannot specify more than one VRF with the mpls ldp session protection command. To specify multiple VRFs, issue the command multiple times. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_ldp/configuration/15-s/mp-ldp-15-s-book/mp-ldp-sessn-prot.pdf

What about Option D? Don't we have to configure the LDP session protection for the neighbors that dont have it ?

Answer should be A since ALL VRF's need protection and thus no limiting as such needs to be put into place. The latter would be done by providing the VRF keyword or doing it per VRF which is not the question in this case.

Sorry, need to correct my own answer. It is A, because configure is also a key word. It is configuring globally and not within each individual VRF instance. You need to issue the command for each VRF globally.

The statement explicitly stated "all VRFs". So The answer is B. Because qouted tekst from link: "You can use the vrf keyword to select which virtual routing and forwarding (VRF) instance is to be protected if the device is configured with at least one virtual private network (VPN) VRF instance. You cannot specify more than one VRF with the mpls ldp session protection command. To specify multiple VRFs, issue the command multiple times."

A for the following reason: 1 - "The default behavior of the mpls ldp session protection command allows MPLS LDP Session Protection for ALL neighbor sessions. You can issue either the vrf or for keyword to limit the number of neighbor sessions that are protected: The wording "on the device only" only is used to distinguish from the other answer "on the device AND on each neighbor..." The question does not tell us it does NOT need to be configured somewhere, only that on "all VRFs on the router" it is not enabled. So to enable it globally will fix it. The question is asking about a "single Cisco device" so we don't care about any other devices. B - again we do not need to enable it within the individual VRFs if we do it globally C - pure nonsense D - configuring it globally makes it unnecessary to ALSO configure on the individual VRFs so this makes no sense

I think the difference here is that the "A" answer includes the "on the device only" parameter. If LDP Session Protection isn't configured on the other nodes as well, it isn't gonna work. So i'm gonna go with B

A - The default behavior of the mpls ldp session protection command allows MPLS LDP Session Protection for all neighbor sessions.

From the link provided - The mpls ldp session protection command entered without a keyword protects all LDP sessions.

correct answers appears B