Juniper JN0-664 Exam With Confidence Using Practice Dumps

Option A (Correct):

In IS-IS, the Designated Intermediate System (DIS) is elected based on the highest configured priority (as defined in Junos OS).

If priorities are equal, the router with the highest MAC address becomes the DIS.

A priority value of 10 will always override a lower priority (e.g., 1).

In the exhibit, we see two VRF (Virtual Routing and Forwarding) instances, CE-1 and CE-2, configured on a Juniper router. Each VRF is associated with a route-distinguisher (RD) and a vrf-target value.

Understanding the Role of vrf-target

The vrf-target is used to define Route Targets (RT), which control the import and export of VPN routes in MPLS Layer 3 VPNs (L3VPNs).

If two VRFs share the same RT, they will import each other's routes, allowing communication between them.

In this case, both VRFs have the same vrf-target:

vrf-target target:65512:100;

Since both CE-1 and CE-2 have the same RT (65512:100), they will import and export each other’s routes, enabling route sharing between them.

Understanding route-distinguisher (RD)

The RD (Route Distinguisher) only ensures uniqueness of overlapping IP prefixes within the MPLS network.

It does not control route sharing between VRFs.

In the exhibit, both VRFs have the same RD (65512:1), but this does not influence whether they share routes.

Correct Answer Selection

A (Correct): The vrf-target configuration enables route sharing between CE-1 and CE-2 since they have the same RT (65512:100).

B (Incorrect): The vrf-target does the opposite—it allows sharing, not blocking.

C (Incorrect): The route-distinguisher only provides unique route identification, but does not affect route sharing.

D (Incorrect): Again, route-distinguisher has no impact on route sharing.

Reference from Juniper Official Documentation

✅ Juniper Documentation - Junos MPLS VPNs Configuration Guide:

"Route targets (vrf-target) are used to control the import and export of VPN routes between different VRFs. VRFs with the same route target can import and export routes to each other, enabling inter-VRF communication."

Thus, the correct answer is:

✅ A. The vrf-target configuration will allow routes to be shared between CE-1 and CE-2.

AToM (Any Transport over MPLS) is a framework that supports various Layer 2 transport types over an MPLS network core. One of the transport types supported by AToM is LDP Layer 2 circuit, which is a point-to-point Layer 2 connection that uses LDP for signaling and MPLS for forwarding. LDP Layer 2 circuit can support Layer 2 connectivity without using BGP and can be scalable and efficient by using a single MPLS LSP for multiple VPN connections. The customer can maintain all routing for their private network by using their own CE switches.