An engineer is troubleshooting L3VPN traffic loss over the MPLS-enabled core network when new core links were enabled.
Assuming that the IGP is properly configured, which issue causes a temporary data flow blackholing when the IGP and LDP reconverges?
Click on the arrows to vote for the correct answer
A. B. C. D.C.
When new core links are enabled, it is common for the IGP and LDP to reconverge. During this time, temporary data flow blackholing can occur. Let's take a look at the potential causes of this issue based on the given answer choices:
A. LDP is a Layer 2 protocol forwarding label packets before the IGP reconverged.
This answer is incorrect because LDP is not a Layer 2 protocol. It is a Layer 3 protocol used to distribute labels across an MPLS network.
B. MP-BGP sessions between PE and RR routers require extra time to reconverge than the underlying IGP.
This answer is partially correct. When a new core link is enabled, the IGP will reconverge first, followed by MP-BGP sessions between PE and RR routers. This can cause a temporary data flow blackholing issue because traffic may be forwarded based on outdated information until the MP-BGP sessions reconverge.
C. IP packets are forwarded as soon as routes are learned over a new IGP adjacency before the label exchange happens over the new links.
This answer is also partially correct. When a new core link is enabled, the IGP will reconverge first, followed by the label exchange over the new links. During this time, traffic may be forwarded based on outdated information until the label exchange is completed.
D. MPLS-TE tunnels without LDP adjacencies are used over the new links black-holing the traffic: before the LDP label exchange is completed.
This answer is incorrect because MPLS-TE tunnels are typically used to optimize traffic engineering in an MPLS network, and they do not cause temporary data flow blackholing during IGP and LDP reconvergence.
In conclusion, the most likely cause of temporary data flow blackholing when the IGP and LDP reconverge after new core links are enabled is due to the delay in MP-BGP sessions between PE and RR routers reconverging, or due to the forwarding of IP packets based on outdated information before the label exchange is completed over the new links.