JN0-664 Sample Questions & Answers

Configuring a scheduler with priority strict-high ensures that the queue for the voice-traffic forwarding class will be serviced until it is empty before any lower-priority queues are serviced. This provides the lowest possible latency. Combining this with a transmit-rate (e.g., transmit-rate 5m) guarantees a minimum amount of bandwidth for this traffic. The strict-high priority handles the real-time requirement, while the transmit rate ensures its bandwidth needs are met. Other queues are not starved because once the strict-high queue is empty, the scheduler moves on to service the other queues.

A Not-So-Stubby Area (NSSA) is a special area type that allows the injection of external routes via an ASBR while still blocking external routes (Type 5 LSAs) from the rest of the OSPF domain. External routes redistributed into an NSSA are carried in Type 7 LSAs, which are only flooded within that NSSA. When these Type 7 LSAs reach the NSSA's Area Border Router (ABR), the ABR translates them into standard Type 5 LSAs and floods them into the backbone area (area 0) and subsequently to other non-stub areas.

This statement is true. LDP-signaled VPLS relies on a full mesh of pseudowires between all participating PE devices to create the multipoint-to-multipoint LAN service. Each pseudowire is signaled using a dedicated targeted-LDP session between the two PE loopback addresses. This requirement is a primary scaling limitation of LDP VPLS, which BGP-signaled VPLS and EVPN were designed to overcome.

When a BGP route's accumulated penalty surpasses the configured suppress threshold, BGP route damping marks the route as hidden or suppressed. In this state, the route is no longer considered a candidate for the best path, it is not installed in the forwarding table, and it is not advertised to any BGP neighbors. The route will remain suppressed until its penalty decays below the reuse threshold.

In Junos OS, policers are typically applied to interfaces as an action within a firewall filter. The correct procedure is to define the policer under [edit firewall], create a firewall filter under [edit firewall family inet filter] that uses the policer as a then action (e.g., then policer my-policer), and finally apply this filter to the interface's input traffic using set interfaces ge-0/0/1 unit 0 family inet filter input my-filter.

The default IS-IS metric (narrow metric) is limited to a maximum value of 63 per link and a total path metric of 1023. To overcome this limitation, IS-IS was extended to support 'wide metrics', which use a 24-bit field, allowing for much larger and more granular metric values. Enabling wide metrics across the entire IS-IS domain is the standard solution to support large-scale networks and prevent metric overflow issues.

PIM uses IGMP on router interfaces connected to receiver segments to manage group membership. The router, acting as an IGMP querier, sends periodic Membership Queries onto the LAN. If any host on that segment is a member of the multicast group, it will respond with an IGMP Membership Report. If the router receives at least one report for a group, it knows it must continue forwarding traffic for that group out the interface. If no reports are received after a timeout, the router prunes the interface from the multicast distribution tree for that group.

A fundamental rule for OSPF virtual links is that the area through which the virtual link is configured (the transit area) cannot be a stub area of any kind (stub, totally stubby, NSSA, or totally NSSA). This is because stub areas are designed to block certain types of LSAs (specifically Type 4 and 5) to reduce the size of their link-state databases. A virtual link relies on the transit area having a full routing table to establish connectivity, which is not possible in a stub area.