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The exhibit shows that the Label Switched Path (LSP) is down. One common reason for this could be that the IGP is not providing traffic engineering information to the MPLS process. Since the exhibit shows the OSPF configuration, enabling traffic engineering extensions for OSPF would allow OSPF to distribute the labels and traffic engineering information necessary for LSP establishment.

References

Juniper Networks Technical Documentation on MPLS and OSPF

https://www.networkfuntimes.com/junos-aggregate-routes-vs-generate-routes-how-to-summarise-on-juniper-routers/

Generated routes are a type of route that can be created to summarize and generate more specific routes within the routing table. Unlike aggregate routes, which summarize existing routes and inherit a next-hop, generated routes do not necessarily have to match an existing route and will have a next-hop of reject by default unless specified otherwise.

References

Juniper Networks Technical Documentation on Routing Policies and Route Generation

In MPLS (Multiprotocol Label Switching) networks, routers use label switching to forward packets. The first router at the edge of the MPLS network (R1) will perform a lookup in the mpls.0 table to determine the label to attach to the packet as it enters the MPLS network. This label informs the next routers in the MPLS network (like R2) on how to forward the packet. Internal MPLS routers, like R2, also perform lookups in their mpls.0 table to determine how to switch the packet toward its destination (label swapping). The inet.3 table is used for resolving next-hop information for labeled routes, but it's the mpls.0 table that is used for label switching decisions.

According to the exhibit, the primary LSP is configured with a strict path via R2 to R4. Since the configuration shows valid next-hops and there is no indication of any issues, the primary LSP will be signaled and its state will be up. The secondary LSP with any-path is also configured and will be signaled as a backup; therefore, its state will be up as well, ready to take over if the primary fails.

BGP selects the active route based on an ordered list of attributes. The correct order is:

Weight (Cisco proprietary, not listed in the options)

Local Preference

Network (route) originated from the BGP router itself

Shortest AS Path

Lowest Origin Type

Lowest MED

eBGP over iBGP paths

Closest IGP Neighbor

Lowest Router ID

The next hop is checked for reachability but is not part of the BGP decision process for selecting the best path.

References

Juniper Networks Technical Documentation on BGP

To influence the path taken through an autonomous system, the Multi-Exit Discriminator (MED) attribute can be used. By setting a lower MED on R2 for routes advertised to R1 and R3, it will make the path through R2 to the 203.0.113.0/24 network more preferable.

In the given exhibit, interface ge-0/0/0 is configured to accept VLANs 101-120 and ge-0/0/1 is configured with flexible VLAN tagging, which means it can tag traffic with any VLAN ID specified. However, only VLAN 200 is explicitly mentioned for ge-0/0/1.

A. Traffic tagged with VLAN 101 will pass through ge-0/0/0 and will egress on ge-0/0/1 with the same VLAN tag, because the VLAN ID is within the allowed range on both interfaces.

B. VLAN 100 is not specified in the allowed VLAN range for ge-0/0/0 (which is 101-120), nor is it specified under ge-0/0/1. Therefore, it will be dropped.

To enable MPLS on a physical interface in Junos, the family mpls statement must be added to the interface configuration. Additionally, the interface itself must be specified under the protocols mpls section of the configuration.

In Junos OS, traffic engineering extensions for OSPF, which are required for an LSP to use the OSPF link state database for path computations, are not enabled by default. They must be explicitly enabled in the OSPF configuration. Therefore, answer C is correct. Answer B is incorrect and contradicts C. The 'no-cspf' command would disable CSPF (Constrained Shortest Path First), which is used for path computations in MPLS traffic engineering, so it should not be used if you want the LSP to utilize OSPF's link state database for path computations. Therefore, answer A is incorrect. The 'policing' parameter is not relevant to enabling traffic engineering extensions in OSPF, so answer D is incorrect.

A Level 1 router can become adjacent with the Level 1 and Level 1-2 (L1/L2) router. A Level 2 router can become adjacent with Level 2 or Level 1-2 (L1/L2) router. There is no adjacency between L1 only and L2 only router. HOWEVER: If two routers are in different areas, they can only form a Level 2 adjacency. As such, two routers in different areas can NOT form a Level 1 adjacency. If you want two routers to form a Level 1 adjacency, they have to be in the same area.

IS-IS (Intermediate System to Intermediate System) operates at two levels: Level 1 and Level 2. Level 1 routers are only aware of their own area's topology, while Level 2 routers have knowledge of the topology across areas. A Level 1 router cannot form an adjacency with a Level 2 router unless the Level 2 router is also operating as a Level 1 router (Level 1-2 router). Level 2 routers can form adjacencies regardless of their area IDs because Level 2 operates at the domain level and is used to interconnect different IS-IS areas.

References

Juniper Networks Technical Documentation on IS-IS

IS-IS Levels and Areas Explanation - Juniper Networks