JNCIA MPLS and VPNs 2

Question 1

In Junos L3VPN, what is the function of a Route Target (RT)?

Accepted Answer

Controls which VRFs import which VPNv4 routes, implementing the VPN topology (full-mesh, hub-spoke, extranet)

Answer

Uniquely identifies each VPN route in the global BGP table

Answer

Specifies the MPLS label value for the VPN

Answer

Sets the routing metric within the VPN

Question 2

What is VPLS (Virtual Private LAN Service) in Junos?

Accepted Answer

A Layer 2 VPN service that provides multipoint Ethernet connectivity across an MPLS network, emulating a LAN switch for geographically dispersed sites

Answer

A Layer 3 routing-based VPN similar to L3VPN

Answer

A point-to-point Layer 2 circuit replacement for leased lines

Answer

A Juniper-proprietary VPN protocol

Question 3

How does Junos implement MPLS traffic engineering (TE)?

Accepted Answer

Using RSVP-TE to signal LSPs with explicit routes and bandwidth reservations, with OSPF or IS-IS TE extensions advertising link bandwidth

Answer

Using BGP to distribute MPLS labels with bandwidth constraints

Answer

Through static MPLS label assignments with manual path configuration

Answer

Traffic engineering is handled automatically by LDP

Question 4

What is 'fast reroute' (FRR) in Junos MPLS?

Accepted Answer

A protection mechanism that pre-computes backup paths for LSPs, enabling sub-50ms traffic rerouting upon link or node failure without waiting for IGP reconvergence

Answer

A method to quickly re-establish failed BGP sessions

Answer

A feature that automatically reroutes traffic based on load

Answer

A rapid OSPF reconvergence technique

Question 5

In Junos, what command shows the MPLS label forwarding table?

Accepted Answer

show route table mpls.0

Answer

show mpls labels

Answer

show forwarding-table mpls

Answer

show label-table

Question 6

What is Segment Routing (SR-MPLS) and how does it differ from LDP-based MPLS?

Accepted Answer

SR-MPLS encodes the entire path in the packet header as a stack of node/adjacency SIDs, eliminating per-flow state in the network core and simplifying operations

Answer

SR-MPLS uses BGP instead of OSPF for path computation

Answer

SR-MPLS requires dedicated hardware not used by traditional MPLS

Answer

SR-MPLS only works with IPv6 traffic