Juniper JN0-664 Exam With Confidence Using Practice Dumps

OSPF uses different types of LSAs to describe different aspects of the network topology. Type 1 LSAs are also known as router LSAs, and they describe the links and interfaces of a router within an area. Type 3 LSAs are also known as summary LSAs, and they describe routes to networks outside an area but within the same autonomous system (AS). By default, OSPF will summarize routes from Type 1 LSAs into Type 3 LSAs when advertising them across area boundaries .

BGP signaled Layer 2 VPN is a type of VPN that uses BGP to distribute VPN labels and information for Layer 2 connectivity between sites over an MPLS network. BGP signaled Layer 2 VPN requires the support of the l2vpn NLRI on all core BGP devices1. The l2vpn NLRI is a new address family that carries Layer 2 VPN information such as the VPN identifier, the attachment circuit identifier, and the route distinguisher. The l2vpn NLRI is used for both auto-discovery and signaling of Layer 2 VPNs2. In this scenario, we are configuring a BGP signaled Layer 2 VPN across an MPLS enabled core network. Therefore, we need to ensure that all core BGP devices support the l2vpn NLRI.

References: 1: 2:

For a Layer 3 VPN to function correctly, an MPLS Label Switched Path (LSP) must be established between the Provider Edge (PE) routers. The MPLS LSP is necessary for the transport of VPN traffic across the service provider's backbone network. If the MPLS LSP is not established, the PE routers cannot forward the VPN traffic properly, causing the routes to be hidden in the BGP routing table.

Here’s a breakdown of why the other options are less likely:

A. The routes use overlapping IP addresses.

Overlapping IP addresses might cause issues with route advertisement and selection, but they would not typically cause routes to be hidden in the bgp.l3vpn.0 table.

C. There is a routing loop in the service provider backbone.

While routing loops are problematic, they would not specifically cause the routes to be hidden in the bgp.l3vpn.0 table. Routing loops would more likely result in dropped packets or increased latency.

D. Route targets are not configured.

Incorrect or missing route target configuration would prevent routes from being imported into the correct VRF, but it would not usually result in the routes being hidden. Instead, they would simply not appear in the relevant VRF.

Thus, the absence of an established MPLS LSP is the most plausible cause for the routes being hidden.