Juniper JN0-351 Enterprise Routing and Switching, Specialist (JNCIS-ENT) Online Training

Question #11

Which statement is correct about IP-IP tunnels?

A . IP-IP tunnels only support encapsulating IP traffic.
B . IP-IP tunnels only support encapsulating non-IP traffic.
C . The TTL in the inner packet is decremented during transit to the tunnel endpoint.
D . There are 24 bytes of overhead with IP-IP encapsulation.

Question #12

You are configuring an IS-IS IGP network and do not see the IS-IS adjacencies established. In this scenario, what are two reasons for this problem? (Choose two.)

A . MTU is not at least 1492 bytes.
B . IP subnets are not a /30 address.
C . The Level 2 routers have mismatched areas.
D . The lo0 interface is not included as an IS-IS interface.

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Question #13

You are asked to create a new firewall filter to evaluate Layer 3 traffic that is being sent between VLANs. In this scenario, which two statements are correct? (Choose two.)

A . You should create a family Ethernet-switching firewall filter with the appropriate match criteria and actions.
B . You should apply the firewall filter to the appropriate VLAN.
C . You should create a family inet firewall filter with the appropriate match criteria and actions.
D . You should apply the firewall filter to the appropriate IRB interface.

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Correct Answer: CD
CD

Explanation:

A firewall filter is a configuration that defines the rules that determine whether to forward or discard packets at specific processing points in the packet flow. A firewall filter can also modify the attributes of the packets, such as priority, marking, or logging. A firewall filter can be applied to various interfaces, protocols, or routing instances on a Juniper device1.

A firewall filter has a family attribute, which specifies the type of traffic that the filter can evaluate. The family attribute can be one of the following: inet, inet6, mpls, vpls, iso, or ethernet-switching2. The family inet firewall filter is used to evaluate IPv4 traffic, which is the most common type of Layer 3 traffic on a network.

To create a family inet firewall filter, you need to specify the appropriate match criteria and actions for each term in the filter. The match criteria can include various fields in the IPv4 header, such as source address, destination address, protocol, port number, or DSCP value. The actions can include accept, discard, reject, count, log, policer, or next term3.

To apply a firewall filter to Layer 3 traffic that is being sent between VLANs, you need to apply the filter to the appropriate IRB interface. An IRB interface is an integrated routing and bridging interface that provides Layer 3 functionality for a VLAN on a Juniper device. An IRB interface has an IP address that acts as the default gateway for the hosts in the VLAN. An IRB interface can also participate in routing protocols and forward packets to other VLANs or networks4.

Therefore, option C is correct, because you should create a family inet firewall filter with the appropriate match criteria and actions. Option D is correct, because you should apply the firewall filter to the appropriate IRB interface.

Option A is incorrect, because you should not create a family ethernet-switching firewall filter with the appropriate match criteria and actions. A family ethernet-switching firewall filter is used to evaluate Layer 2 traffic on a Juniper device. A family ethernet-switching firewall filter can only match on MAC addresses or VLAN IDs, not on IP addresses or protocols5.

Option B is incorrect, because you should not apply the firewall filter to the appropriate VLAN. A VLAN is a logical grouping of hosts that share the same broadcast domain on a Layer 2 network. A VLAN does not have an IP address or routing capability. A firewall filter cannot be applied directly to a VLAN; it must be applied to an interface that belongs to or connects to the VLAN6.

Reference: 1: Firewall Filters Overview 2: Configuring Firewall Filters 3: Configuring Firewall Filter Match

Conditions and Actions 4: Understanding Integrated Routing and Bridging Interfaces 5: Configuring

Ethernet-Switching Firewall Filters 6: Understanding VLANs

Question #14

Exhibit

You have configured a GRE tunnel. To reduce the risk of dropping traffic, you have configured a keepalive OAM probe to monitor the state of the tunnel; however, traffic drops are still occurring.

Referring to the exhibit, what is the problem?

A . For GRE tunnels, the OAM protocol requires that the BFD protocols also be used.
B . The "event link-adjacency-loss" option must be set.
C . LLDP needs to be removed from the gr-1/1/10.1 interface.
D . The hold-time value must be two times the keepalive-time value

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Correct Answer: D
D

Explanation:

A keepalive OAM probe is a mechanism that can be used to monitor the state of a GRE tunnel and detect any failures in the tunnel path. A keepalive OAM probe consists of sending periodic packets from one end of the tunnel to the other and expecting a reply. If no reply is received within a specified time, the tunnel is considered down and the line protocol of the tunnel interface is changed to down1.

To configure a keepalive OAM probe for a GRE tunnel, you need to specify two parameters: the keepalive-time and the hold-time. The keepalive-time is the interval between each keepalive packet sent by the local router. The hold-time is the maximum time that the local router waits for a reply from the remote router before declaring the tunnel down2.

According to the Juniper Networks documentation, the hold-time value must be two times the keepalive-time value for a GRE tunnel2. This is because the hold-time value must account for both the round-trip time of the keepalive packet and the processing time of the remote router. If the hold-time value is too small, it may cause false positives and unnecessary tunnel flaps.

In the exhibit, the configuration shows that the keepalive-time is set to 10 seconds and the hold-time

is set to 15 seconds for the gr-1/1/10.1 interface. This means that the local router will send a keepalive packet every 10 seconds and will wait for 15 seconds for a reply from the remote router. However, this hold-time value is not two times the keepalive-time value, which violates the recommended configuration. This may cause traffic drops if the remote router takes longer than 15 seconds to reply.

Therefore, option D is correct, because the hold-time value must be two times the keepalive-time value for a GRE tunnel. Option A is incorrect, because BFD is not required for GRE tunnels; BFD is another protocol that can be used to monitor tunnels, but it is not compatible with GRE keepalives3. Option B is incorrect, because the “event link-adjacency-loss” option is not related to GRE tunnels; it is an option that can be used to trigger an action when a link goes down4. Option C is incorrect, because LLDP does not need to be removed from the gr-1/1/10.1 interface; LLDP is a protocol that can be used to discover neighboring devices and their capabilities, but it does not interfere with GRE tunnels5.

Reference:

1: Configuring Keepalive Time and Hold time for a GRE Tunnel Interface 2: keepalive | Junos OS |

Juniper Networks 3: Configuring Bidirectional Forwarding Detection 4: event link-adjacency-loss |

Junos OS | Juniper Networks 5: Understanding Link Layer Discovery Protocol

Question #15

Exhibit

You are a network operator troubleshooting BGP connectivity.

Which two statements are correct about the output shown in the exhibit? (Choose two.)

A . Peer 10.32.1.2 is configured for AS 63645.
B . The BGP session is not established.
C . The R1 is configured for AS 65400.
D . The routers are exchanging IPv4 routes.

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Question #16

What is the maximum allowable MTU size for a default GRE tunnel without IPv4 traffic fragmentation?

A . 1496 bytes
B . 1480 bytes
C . 1500 bytes
D . 1476 bytes

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Question #17

You are a network operator who wants to add a second ISP connection and remove the default route to the existing ISP You decide to deploy the BGP protocol in the network.

What two statements are correct in this scenario? (Choose two.)

A . IBGP updates the next-hop attribute to ensure reachability within an AS.
B . IBGP peers advertise routes received from EBGP peers to other IBGP peers.
C . IBGP peers advertise routes received from IBGP peers to other IBGP peers.
D . EBGP peers advertise routes received from IBGP peers to other EBGP peers.

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Question #18

You are troubleshooting a BGP routing issue between your network and a customer router and are reviewing the BGP routing policies.

Which two statements are correct in this scenario? (Choose two.)

A . Export policies are applied to routes in the RIB-ln table.
B . Import policies are applied to routes in the RIB-Local table.
C . Import policies are applied after the RIB-ln table.
D . Export policies are applied after the RIB-Local table.

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Question #19

You are asked to connect an IP phone and a user computer using the same interface on an EX Series switch. The traffic from the computer does not use a VLAN tag, whereas the traffic from the IP phone uses a VLAN tag.

Which feature enables the interface to receive both types of traffic?