Select Two (Multi-Select) Questions

The route to the source points towards a null or reject route.

If the RPF lookup resolves to a reject or discard route, the RPF check fails.

There is no matching route in the unicast routing table or MBGP table for the source IP address.

A missing route to the source results in an automatic RPF failure.

The incoming interface of the multicast packet does not match the outgoing interface of the RPF route towards the source.

If a packet arrives on an interface different from the route's next-hop interface, an RPF failure occurs.

discard

A policer's discard action drops excess traffic immediately at the interface, enforcing the committed rate without buffering. This satisfies the stem's requirement for actions triggered when traffic exceeds the specified rate, since discarding is one of the three standard policer outcomes alongside rate-limiting and marking.

loss-priority high

Marking packets with high loss-priority makes them the first discarded during congestion, so the policer enforces the committed rate while allowing bursty traffic to pass. This is one of the three actions a policer can apply, alongside discard and forwarding.

forward

A policer's forward action passes out-of-profile traffic through unchanged, without marking or discarding it. This satisfies the question's requirement by naming a valid policer action alongside discard and loss-priority marking, allowing excess packets to proceed.

A Designated Forwarder is elected to forward BUM traffic from the core to the multi-homed site.

The DF is responsible for sending BUM traffic down to the attached customer site.

Segment preference values and IP addresses are evaluated to determine the forwarding role deterministically.

The DF algorithm uses configured segment preferences and router IPs as tie-breakers.

PE routers exchange Route Type 4 (Ethernet Segment Routes) to discover peers attached to the same segment.

Type 4 routes advertise ESI reachability and enable PEs to discover each other on the same segment.

A route reflector must never reflect routes received from a non-client peer back to other non-client peers.

Standard iBGP full-mesh rules apply between non-client peers; a route reflector reflects routes from clients to all clients and non-clients, and from non-clients to clients only.

The Originator ID attribute is added by the route reflector to prevent routing loops from client peers.

The route reflector adds the Originator ID to ensure that if the originator receives its own advertised route back, it ignores it.

Redundant route reflectors within the same cluster must be configured with the same cluster ID.

Sharing a cluster ID prevents redundant route reflectors from accepting and reflecting routes back and forth infinitely.

It uses sequence numbers attached to Type-2 routes to track host movement between different PEs.

EVPN MAC mobility relies on sequence numbers carried in Type-2 (MAC/IP Advertisement) routes, allowing every PE to determine the most recent advertisement for a given MAC. When a host moves to another PE, the higher sequence number wins, so stale entries are withdrawn and traffic follows the host, satisfying the requirement to track movement between PEs.

It prevents traffic blackholing when a virtual machine or host moves from one multi-homed attachment circuit to another.

EVPN MAC mobility advertises the moved MAC with an incremented sequence number, letting remote peers withdraw the stale path and relearn the new one. That mechanism directly prevents traffic blackholing when a virtual machine or host moves between multi-homed attachment circuits, satisfying the stem's mobility constraint.

Modify the OSPF route metric using the metric action.

The export policy's metric action assigns the OSPF external metric carried in the AS-external LSA when redistributing routes into OSPF. This satisfies the stem's requirement, letting the filter control the advertised cost of redistributed routes rather than relying on defaults.

Set the external metric type to Type-1 or Type-2.

Redistribution into OSPF accepts an export policy that sets the external metric type, choosing Type-1 (metric added to internal cost) or Type-2 (metric fixed regardless of path). This directly satisfies the stem's requirement, since the export filter controls how redistributed routes are advertised.

VLAN action rules (pop, push, or swap)

VLAN action rules define whether the provider edge pushes, pops or swaps tags as frames traverse the tunnel. Aligning these operations on both sides preserves the customer's inner VLAN while adding the service tag, which is the core mechanism of Q-in-Q forwarding.

Tag Protocol Identifier (TPID) EtherType values

The TPID EtherType identifies whether a frame carries an outer service tag, so customer and provider edges must agree on its value (typically 0x8100 or 0x88a8). Mismatched EtherTypes cause the provider edge to misread or discard tunnelled frames, breaking Q-in-Q encapsulation entirely.

Flexible VLAN tagging enabled on physical interfaces

Flexible VLAN tagging lets a single physical interface accept both single-tagged and dual-tagged frames, which is essential when customer and provider edges disagree on tag depth. Enabling it on the physical interfaces ensures Q-in-Q frames are not dropped before the VLAN action rules process them.

Enabling OSPFv3 under the protocols ospf3 hierarchy

OSPFv3 is configured under protocols ospf3.

Assigning interfaces to OSPFv3 areas

Interfaces must be explicitly added to OSPFv3 areas.

Defining OSPFv3 area identifiers

Areas must be defined under protocols ospf3.

It automates network policy configuration for voice, video, and guest VLANs.

LLDP-MED network policy TLVs let the switch push VLAN ID, 802.1p priority and DSCP values to attached endpoints, so voice, video and guest traffic land in the correct VLAN automatically. This is the policy automation behaviour Junos EX Series implements for media endpoints.

It allows the switch to exchange location identification information with emergency-capable endpoints.

LLDP-MED location identification TLVs carry civic address, coordinate or ECS ELIN data from the switch to emergency-capable endpoints, such as IP phones. The endpoint forwards this to the PSAP during an emergency call, satisfying the location exchange behaviour the question describes.

It provides inventory management by advertising hardware, software, and serial number details from the endpoint.

LLDP-MED inventory management TLVs advertise model, firmware, software and serial number data from the endpoint to the switch. Junos EX Series stores this in its LLDP neighbour database, giving administrators asset visibility without manual auditing, which is the inventory management behaviour the question tests.

mac-radius

MAC-RADIUS combines MAC address authentication with RADIUS, letting the switch authenticate a device by its MAC before any 802.1X supplicant responds. This satisfies the stem's requirement for a valid authentication-order method, since Junos accepts mac-radius alongside dot1x, captive-portal and mac-radius-restrict on EX Series interfaces.

dot1x

Dot1x is a valid entry in the authentication-order statement, letting the switch attempt IEEE 802.1X port-based authentication before falling through to later methods. It satisfies the stem's requirement for a specifiable method on an EX Series interface, where supplicants authenticate via EAPOL before network access is granted.

Weight (local to the router)

Weight is evaluated first in Junos BGP path selection.

Local Preference

Local preference is evaluated after weight.

MED (Multi-Exit Discriminator)

MED is evaluated during the standard selection steps before router ID.

Run 'show pim join' to inspect upstream neighbor information and verify the RPF interface for the source.

The 'show pim join' command displays PIM join state and confirms the upstream RPF neighbor toward the source or RP.

Run 'show igmp group' to verify that receivers have successfully joined the multicast group on the local interface.

Checking local IGMP membership via 'show igmp group' ensures that receivers are actively requesting the stream on the last-hop router.

Run 'show multicast route' to verify if (S,G) or (*,G) entries exist and check packet forwarding counters.

'show multicast route' displays the installed (S,G) and (*,G) forwarding entries plus packet counters, confirming whether the specific source's traffic is being forwarded or dropped, which directly verifies the multicast forwarding state and RPF path on the Junos router.

show ospf neighbor

`show ospf neighbour` displays adjacency states and the router IDs of peers, exposing stuck ExStart or Exchange states that indicate MTU mismatches or mismatched authentication. This directly satisfies the stem's requirement for an OSPF troubleshooting command, since neighbour formation failures are the most common cause of missing routes.

show ospf database

`show ospf database` inspects the link-state advertisements held in the device's OSPF link-state database, revealing each LSA's type, age, sequence number and advertising router. This exposes adjacency or flooding problems — such as mismatched LSAs or missing routes — satisfying the stem's requirement for an OSPF troubleshooting command on Junos.

The BSR collects Candidate-RP messages and periodically distributes the RP-set to all PIM routers.

The BSR gathers Candidate-RP advertisements and floods the resulting RP-set to every PIM router in the domain, enabling group-to-RP mapping without static configuration. This satisfies the dynamic RP discovery requirement, since routers learn which RPs serve which multicast groups.

All PIM routers in the domain dynamically learn the RP-set from the BSR messages.

BSR messages carry the RP-set to every PIM router via hop-by-hop flooding, so each router learns candidate RPs dynamically without manual configuration. This satisfies the stem's requirement for dynamic RP-set distribution across the domain, unlike static RP configuration where each router must be configured individually.

They can specify the Layer 2 priority and DSCP values for QoS.

Network policy TLVs include Layer 2 priority (802.1p) and DSCP values, enabling the phone to mark voice traffic appropriately for QoS. This ensures that voice packets are prioritized across the network. These parameters are essential for maintaining voice quality in congested networks.

They can specify the VLAN ID for voice traffic.

LLDP-MED network policy TLVs include the VLAN ID, which tells the phone which VLAN to use for voice traffic. This is a key function of LLDP-MED, allowing the phone to tag voice frames with the correct VLAN. Without this, the phone would not know which VLAN to use, potentially causing connectivity issues.

Drop profile curves plot drop probability against queue buffer fill level

The graph maps drop probability versus fill level percentage.

Drop profiles help prevent TCP global synchronization by dropping packets before buffers are completely full

RED drops packets early to signal TCP senders.

The switch moves authenticating clients into a designated critical VLAN or applies a critical profile.

When the RADIUS server is unreachable, the switch places newly authenticating supplicants into a designated critical VLAN or applies a critical profile, preserving network access rather than denying it. This satisfies the stem's fallback requirement, since critical authentication specifically handles server-unreachable conditions on EX Series switches.

Critical authentication can be configured separately for 802.1X and MAC RADIUS authentication methods.

Critical authentication is configured independently per authentication method, so 802.1X supplicants and MAC RADIUS devices each retain their own fallback settings. This satisfies the scenario's requirement that fallback behaviour be tunable separately when the RADIUS server becomes unreachable, letting one method's critical VLAN differ from the other's without affecting either.

The switch continues to probe the primary RADIUS servers at configured intervals to detect recovery.

The switch keeps polling the unreachable primary RADIUS servers at the configured interval, so it can detect when they come back online and resume normal authentication. This satisfies the fallback requirement that recovery is automatic, without administrator intervention, once the primary server becomes reachable again.

show vstp vlan

Displays VSTP status per VLAN.

show vstp interface

Displays VSTP operational state and port roles per interface.

Type 1 routes are advertised either per-EVI or per-Ethernet Segment (ES).

Type 1 routes carry the Ethernet Segment Identifier and can be advertised per-EVI or per-Ethernet Segment, satisfying the stem's requirement for valid EVPN auto-discovery behaviour. Per-ES advertisement supports multihoming split-horizon and designated-forwarder election, while per-EVI advertisement applies to single-homed access, so both granularities are legitimate.

Per-EVI Type 1 routes enable multi-homing aliasing so PEs can load balance traffic even before learning a MAC locally.

Per-EVI Type 1 routes advertise each EVI's multihoming state, letting remote PEs install aliasing entries pointing to all attached PEs. This allows load balancing across the Ethernet Segment before any MAC is learned locally, satisfying the aliasing requirement.

An LLDP-MED network policy defining the voice VLAN must be configured and applied to the interface.

LLDP-MED conveys the voice VLAN through a network policy TLV, so an LLDP-MED network policy defining VLAN 50 must exist and be applied to the interface. Without it, no policy is advertised and the phone cannot discover the voice VLAN, satisfying the stem's discovery requirement.

The connected IP phone must support LLDP-MED and be capable of processing network policies.

LLDP-MED network policy TLVs are only interpreted by endpoints implementing the LLDP-MED extension; a phone lacking that support cannot parse the advertised voice VLAN. This satisfies the stem's requirement that the phone discover and use the voice VLAN via LLDP-MED.

LLDP must be enabled globally and on the specific switch interface.

LLDP-MED voice VLAN advertisement requires LLDP active both globally and on the access port facing the phone; without interface-level LLDP, no TLVs are transmitted, so the phone cannot learn the voice VLAN ID or tag its traffic correctly.