Juniper Juniper Certifications JN0-351 Questions & Answers

• Question 171:

  You need to configure a LAG between your switches. In this scenario, which two statements are correct? (Choose two.)

  A. Duplex and speed settings are not required to match on both participating devices.

  B. Duplex and speed settings are required to match on both participating devices.

  C. Member links are not required to be contiguous ports.

  D. Member links are required to be contiguous ports.

  Correct Answer: BC

  B is correct because duplex and speed settings are required to match on both participating devices. According to the Juniper Networks documentation1, all the interfaces in a LAG must have the same speed and be in full-duplex mode. This

  ensures that the LAG can operate as a single logical link without any performance or compatibility issues.

  C is correct because member links are not required to be contiguous ports. According to the Juniper Networks documentation2, you can group any Ethernet interfaces on a switch into a LAG, regardless of their physical location or slot

  number. This provides flexibility and scalability for configuring LAGs on switches.

• Question 172:

  Which statement about aggregate routes is correct?

  A. Aggregate routes can only be used for static routing but not for dynamic routing protocols.

  B. Aggregate routes are automatically generated for all of the subnets in a routing table.

  C. Aggregate routes are always preferred over more specific routes, even when the specific routes have a better path.

  D. Aggregate routes are used for advertising summarized network prefixes.

  Correct Answer: D

  Explanation: Aggregate routes are used for advertising summarized network prefixes12. They help minimize the number of routing tables in an IP network by consolidating selected multiple routes into a single route advertisement1. This

  approach is in contrast to non-aggregation routing, in which every routing table contains a unique entry for each route1.

  Therefore, option D is correct. Options A, B, and C are not correct because:

  Aggregate routes can be used with both static routing and dynamic routing protocols1.

  Aggregate routes are not automatically generated for all of the subnets in a routing table. They need to be manually configured1.

  Aggregate routes are not always preferred over more specific routes. The route selection process in Junos OS considers several factors, including route preference and metric, before determining the active route1.

• Question 173:

  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.

  Correct Answer: CD

  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. References:

  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 174:

  Which two statements about BGP facilitate the prevention of routing loops between two autonomous systems? (Choose two.)

  A. EBGP routers will append their AS number when advertising routes to their neighbors.

  B. EBGP routers will only accept routes that contain their own AS number in the AS_PATH.

  C. EBGP routers will drop routes that contain their own AS number in the AS_PATH

  D. EBGP routers will prepend their AS number when advertising routes to their neighbors

  Correct Answer: AC

  Explanation: BGP (Border Gateway Protocol) is a protocol designed to exchange routing and reachability information among autonomous systems (AS) on the internet1. Option A is correct. When an EBGP router advertises routes to its

  neighbors, it appends its AS number to the AS_PATH attribute1. This is a key mechanism in BGP to prevent routing loops1.

  Option C is correct. BGP has a built-in loop prevention mechanism whereby if a BGP router detects its own AS in the AS_PATH attribute, it will drop the prefix and will not continue to advertise it2. This helps to prevent routing loops2. Option B

  is incorrect. EBGP routers do not accept routes that contain their own AS number in the AS_PATH2. Instead, they drop such routes as part of the loop prevention mechanism2.

  Option D is incorrect. While it's true that EBGP routers append their AS number when advertising routes, they do not prepend their AS number1. The term "prepend" in BGP usually refers to a technique used to influence path selection by

  artificially lengthening the AS_PATH3.

• Question 175:

  Exhibit Referring to the exhibit, which two configuration changes must you apply for packets to reach from R1 to R3 using IS-IS? (Choose two.)

  

  Explanation: A. On R1, enable Level 1 on the ge-0/0/1 interface. In IS-IS, both levels (Level 1 and Level 2) are enabled by default when you enable IS-IS on an interface1. Level 1 systems route within an area2. If the destination is outside an area, Level 1 systems route toward a Level 2 system2. Therefore, enabling Level 1 on the ge-0/0/1 interface on R1 would allow packets to reach from R1 to R3.

  A. On R1, enable Level 1 on the ge-0/0/1 interface.

  B. On R3 disable Level 2 on the ge-0/0/4 interface.

  C. On R1, disable Level 2 on the ge-0/0/1 interface.

  D. On R3 enable Level 1 on the ge-0/0/4 interface

  Correct Answer: AD

  D. On R3 enable Level 1 on the ge-0/0/4 interface Similarly, enabling Level 1 on the ge- 0/0/4 interface on R3 would allow packets to reach from R1 to R3. These explanations are based on the IS-IS configuration documents and learning resources available at Juniper Networks1 and Cisco34.