JNCIP-ENT Practice Test 20 — 15 Questions

Question 1

You are deploying an EVPN-VXLAN fabric on Juniper switches with a multi-homed server connected to two leaf switches in an all-active configuration. The server's MAC address is learned locally on both leaf switches. Which mechanism ensures that only one leaf switch forwards BUM traffic to the server, while both can forward known unicast traffic?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Designated Forwarder (DF) election based on Type 4 routes. In all-active multi-homing, the Designated Forwarder (DF) election, based on Type 4 routes, selects one PE to forward BUM traffic to the multi-homed device. This prevents duplicate BUM packets. Known unicast traffic can be forwarded by any PE because MAC addresses are learned locally and advertised via Type 2 routes, allowing load balancing. Split Horizon, anycast gateway, and aliasing serve different purposes.

Answer

Anycast gateway MAC synchronization

Answer

Split Horizon filtering based on Type 1 routes

Answer

MAC address aliasing using Type 2 routes

Question 2

You are tuning an egress interface on a Junos device for a service provider environment. You have configured three drop profiles and applied them to a scheduler map. You need to verify that the weighted random early detection (WRED) behaviour is operating as intended under congestion. Which TWO statements correctly describe how Junos implements drop profiles and WRED? (Choose two.)

Accepted Answer

Each drop profile defines fill-level thresholds and corresponding drop probabilities that determine which packets are discarded as the queue fills.. Drop profiles in Junos map queue fill levels to drop probabilities and are attached to forwarding classes through schedulers and scheduler maps, which together produce WRED behaviour that ramps up dropping as congestion increases. Statements claiming interface-level override, tail-drop-only operation, or restriction to low-priority queues misdescribe the configuration hierarchy and the gradual nature of weighted random early detection.

Answer

Drop profiles only apply to low-priority queues and are ignored for high-priority forwarding classes.

Answer

WRED drops packets randomly as soon as the queue reaches its configured maximum buffer size, regardless of fill level.

Answer

Drop profiles are applied directly to the physical interface and override any scheduler map configuration.

Question 3

An administrator is configuring BGP multipath on a Junos router. The router has two BGP paths to the same destination: one with a MED of 100 and another with a MED of 200. Both paths are from the same neighboring AS. The administrator wants both paths to be installed in the forwarding table for load balancing. Which configuration is required?

Accepted Answer

Enable multipath under BGP and ensure that the paths have the same MED by using a routing policy to set MED to a common value.. For BGP multipath to install multiple paths, the paths must be equal in terms of MED, among other attributes. If MED values differ, they are not eligible for multipath. The solution is to enable multipath and use a routing policy to set the MED to a common value on both paths, making them equal. This allows the router to load-balance traffic across both paths.

Answer

Configure 'multipath' under BGP and set the 'med' to 'always-compare'.

Answer

Configure 'multipath multiple-as' under BGP and set the MED to the same value on both paths.

Answer

Enable multipath under the BGP group and ensure that the paths have the same MED.

Question 4

You are configuring a Juniper EX Series switch to support a VoIP deployment. You want to ensure that voice traffic from IP phones is placed in VLAN 100 and data traffic in VLAN 200, with the phone tagging voice packets with 802.1p priority 5. Which feature should you configure?

Accepted Answer

Voice VLAN with VLAN ID 100 and 802.1p priority 5, and data VLAN 200 on the access port.. The voice VLAN feature on Juniper EX Series switches enables automatic assignment of voice traffic to a specific VLAN and can set 802.1p priority. By configuring voice VLAN 100 with priority 5 and data VLAN 200, the switch will recognize VoIP traffic (via LLDP-MED or MAC address) and place it in the correct VLAN with the appropriate priority, ensuring QoS for voice.

Answer

Private VLAN with primary VLAN 100 and secondary VLAN 200.

Answer

MSTP with MSTI 1 for VLAN 100 and MSTI 2 for VLAN 200.

Answer

Q-in-Q tunneling with outer VLAN 100 and inner VLAN 200.

Question 5

Which BGP attribute is used to prevent routing loops in a BGP confederation?

Accepted Answer

AS_CONFED_SEQUENCE. In a BGP confederation, the AS_CONFED_SEQUENCE attribute is used to prevent loops within the confederation. It records the sub-AS numbers that a route has traversed. When a router receives a route with its own sub-AS number in the AS_CONFED_SEQUENCE, it detects a loop and rejects the route. This attribute is only used internally within the confederation and is stripped when advertising to external peers. The other attributes serve different purposes.

Answer

ORIGINATOR_ID

Answer

AS_PATH

Answer

CLUSTER_LIST

Question 6

You are configuring an EVPN-VXLAN fabric on Juniper switches. A leaf switch needs to advertise its local VXLAN Tunnel Endpoint (VTEP) address to remote VTEPs so they can establish VXLAN tunnels. Which EVPN route type is used to advertise the VTEP IP address and support BUM traffic replication?

Accepted Answer

Type 3 route (Inclusive Multicast Ethernet Tag route). Type 3 routes, also known as Inclusive Multicast Ethernet Tag routes, advertise the VTEP IP address and VNI. They allow remote VTEPs to discover each other and build replication lists for BUM traffic. This is fundamental for VXLAN tunnel establishment in an EVPN-VXLAN fabric. Type 1, Type 2, and Type 4 routes serve different purposes and do not provide VTEP discovery.

Answer

Type 4 route (Ethernet Segment route)

Answer

Type 2 route (MAC/IP Advertisement route)

Answer

Type 1 route (Ethernet Auto-Discovery route)

Question 7

You are setting up a new EVPN-VXLAN fabric on Juniper switches. You need to configure the BGP session between two PE routers to exchange EVPN routes. Which BGP configuration is required to enable the EVPN address family on the session?

Accepted Answer

family evpn signaling. To exchange EVPN routes between PE routers, the BGP session must be configured with the EVPN address family. On Junos devices, this is done using the 'family evpn signaling' command under the BGP neighbor configuration. This enables the EVPN NLRI and allows the routers to advertise and receive EVPN route types, such as Type 2 MAC/IP Advertisement routes. Without this configuration, the EVPN control plane will not function.

Answer

family inet unicast

Answer

family inet-vpn unicast

Answer

family l2vpn signaling

Question 8

You are troubleshooting an EVPN-VXLAN network where a Juniper MX Series router is acting as a PE. You notice that traffic from a local host to a remote host is being dropped, even though the remote host's MAC address is present in the EVPN database. The BGP EVPN session is up, and Type-2 routes are exchanged. Which of the following is the most likely cause?

Accepted Answer

The VXLAN tunnel to the remote VTEP is not established because the remote VTEP's Type-3 route was not received or processed.. Even if a remote MAC address is learned via Type-2 routes, traffic cannot be forwarded unless a VXLAN tunnel exists to the remote VTEP. The tunnel is established based on Type-3 routes. If the Type-3 route is missing or not processed, the tunnel will not be created, and traffic will be dropped. This is a common troubleshooting step in EVPN-VXLAN networks.

Answer

The local host's MAC address is not being advertised to the remote VTEP, so return traffic cannot reach the local host.

Answer

The remote host's MAC address is learned via a Type-2 route, but the corresponding IP address is not present, causing the traffic to be dropped due to an ARP suppression mismatch.

Answer

The EVPN instance's route target configuration does not match on both PE routers, preventing Type-2 routes from being imported.

Question 9

You are troubleshooting an OSPF adjacency between two Juniper Networks routers on a broadcast Ethernet segment. The routers are in the same area and have matching hello and dead intervals. The adjacency remains in ExStart state. Which OSPF parameter mismatch is the most likely cause?

Accepted Answer

MTU mismatch. OSPF adjacency formation progresses through Down, Init, 2-Way, ExStart, Exchange, Loading, and Full. A stall in ExStart indicates that the routers cannot agree on the master/slave relationship and initial sequence number for database description packets. The most common cause is an MTU mismatch, because the router with the larger MTU may send packets that the other router cannot process, or the DBD packets are rejected. Matching MTU or using the 'ignore-mtu' statement resolves the issue.

Answer

Authentication mismatch

Answer

Area ID mismatch

Answer

Hello interval mismatch

Question 10

You are deploying 802.1X on an EX Series switch and want to ensure that when a supplicant fails authentication, it is placed into a VLAN that provides limited access to a remediation server. Which TWO Junos configuration elements are required to support this behavior? (Choose two.)

Accepted Answer

Configure a guest VLAN under the 802.1X authenticator interface settings. To place failed supplicants into a remediation VLAN, the switch must have a guest VLAN configured under the 802.1X interface settings, and that guest VLAN must correspond to an actual VLAN that provides the intended limited access. These two elements together enable the behavior; other settings such as MAC RADIUS or multiple supplicant mode are not required for guest VLAN assignment.

Answer

Configure the guest VLAN and ensure the interface is in multiple supplicant mode

Answer

Enable MAC RADIUS authentication as the primary method

Answer

Configure the guest VLAN and set the authentication order to include 802.1X

Question 11

A network administrator is configuring CoS on a Junos EX Series switch and wants to verify the mapping between forwarding classes and queues as currently applied to a specific interface. Which operational command should the administrator use to display the forwarding class to queue mapping along with scheduler and classifier details for a given interface?

Accepted Answer

show class-of-service interface. The show class-of-service interface command is the operational command that displays the CoS elements applied to a specific interface, including the classifier, rewrite rule, scheduler map, and the resulting forwarding class to queue mapping. It is the correct tool to verify how classes map to queues on that interface.

Answer

show class-of-service forwarding-class

Answer

show configuration class-of-service

Answer

show interfaces extensive

Question 12

An administrator is troubleshooting a Juniper EX Series switch where an IP phone connected to ge-0/0/10 is not receiving PoE power. The switch is an EX4300 with PoE+ capable ports. The administrator runs 'show poe interface ge-0/0/10' and sees 'Status: Disabled'. The interface is administratively up and LLDP is operational. What is the most likely cause?

Accepted Answer

PoE has been disabled on the interface with the 'disable' command under the PoE hierarchy.. The 'Disabled' status in the PoE interface output specifically indicates that PoE is administratively turned off for that port. This is typically done with the 'disable' command under the PoE interface configuration. Even if the port is up and LLDP is functioning, PoE will not be supplied until it is re-enabled. This is a common misconfiguration when PoE is disabled for power saving or security.

Answer

The connected device does not support IEEE 802.3af/at and is not drawing power.

Answer

LLDP-MED has not been configured on the interface, preventing PoE negotiation.

Answer

The PoE controller has reached its maximum power budget and has disabled the port.

Question 13

You are configuring OSPF on a Juniper Networks router. You want to influence the DR/BDR election on a broadcast segment so that a specific router becomes the DR. Which configuration statement should you apply to the interface?

Accepted Answer

set protocols ospf area 0 interface ge-0/0/0.0 priority 100. In OSPF, the DR and BDR are elected based on the interface priority and, as a tiebreaker, the router ID. The router with the highest priority becomes the DR. On Junos devices, the priority is configured with the 'priority' statement under the OSPF interface. Setting a higher priority increases the chance of being elected DR. The metric, hello-interval, and passive settings do not influence DR election.

Answer

set protocols ospf area 0 interface ge-0/0/0.0 passive

Answer

set protocols ospf area 0 interface ge-0/0/0.0 metric 100

Answer

set protocols ospf area 0 interface ge-0/0/0.0 hello-interval 100

Question 14

An enterprise network runs PIM sparse-mode with a static RP configured on all routers. Users on a VLAN report that they can receive multicast streams from external sources, but the internal server 10.10.5.20 streaming to group 239.1.1.1 was just migrated to a new subnet. After the migration, receivers on a different VLAN stop receiving the stream, even though the new subnet is reachable and PIM is enabled on all interfaces. Which configuration element is most likely missing?

Accepted Answer

The first-hop router connected to the new source subnet must have a route to the RP and PIM enabled on the interface facing the source.. PIM sparse-mode requires the last-hop router to join the shared tree toward the RP, and the first-hop router to register active sources with the RP. When a source moves to a new subnet, the router directly attached to that subnet becomes the new first-hop router. It must have PIM enabled on the source-facing interface and a unicast route to the RP so Register messages can be delivered. Without that, the RP never learns the source and receivers on the shared tree are starved.

Answer

An MSDP peer relationship must be established between the first-hop router and the RP to carry source information.

Answer

The RP must be configured with an anycast address so that both the old and new source subnets can register simultaneously.

Answer

The new source interface must be added under the [edit protocols pim rp static] address configuration as a permitted source.

Question 15

You are deploying 802.1X on an EX Series switch. The security team requires that if the RADIUS server is unreachable during authentication, endpoints that were previously authenticated on a port must not lose network access, but new endpoints must be denied. Which action should you configure under the authenticator's interface to meet this requirement?

Accepted Answer

Configure the interface with the statement server-fail keep, which maintains existing authenticated sessions while denying new supplicants when the RADIUS server is unreachable.. When the RADIUS server is unreachable, the switch must decide how to handle the port. The server-fail keep setting preserves already-authenticated sessions and rejects new authentication attempts, which aligns with the requirement to maintain existing access while denying new endpoints. Other server-fail options either permit all traffic or affect different failure conditions.

Answer

Configure the interface with the statement server-fail permit, which allows all traffic on the port when the RADIUS server is unreachable.

Answer

Configure the interface with the statement server-reject-vlan, which places the port into a restricted VLAN when RADIUS rejects authentication.

Answer

Configure the interface with the statement mac-radius, which enables MAC RADIUS authentication as a fallback mechanism when the RADIUS server is unreachable.