JN0-363 Exam Dumps : Service Provider Routing and Switching, Specialist (JNCIS-SP)

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.

References:

• Juniper Networks documentation on MPLS: MPLS Applications User Guide for Routing Devices

To create connections between routing instances on the same Junos device and route between them, you can use logical tunnel interfaces, which are virtual interfaces that can be used to route traffic between instances without the need for physical connectivity. Additionally, loopback interfaces, which represent the device itself, can be used to route traffic between routing instances as they are always up and can be reached within the device.

References

• Juniper Networks Technical Documentation on Routing Instances
• Juniper Networks Technical Documentation on Logical Tunnel Interfaces

With Label Distribution Protocol (LDP), a full mesh of label-switched paths (LSPs) is automatically created between all LDP-enabled routers, and these paths are reflected in the inet.3 table. LDP LSPs are set up when LDP is enabled on interfaces connecting routers in an MPLS network.

References:

• Juniper Networks documentation on LDP: Understanding LDP