Juniper JN0-351 Enterprise Routing and Switching, Specialist Exam Practice Test

Answer : B, D

The two reasons for the failure to form an adjacency in a network running IS-IS could be:

B) There is no configured ISO address on any IS-IS interface.IS-IS requires each router interface to have an ISO address configured.Without this address, the routers cannot form an adjacency1.

D) The family iso configuration is missing from the adjacency interface.The 'family iso' configuration is essential for IS-IS to function correctly.If this configuration is missing from the adjacency interface, it could prevent the formation of an adjacency1.

These explanations are based on the Enterprise Routing and Switching Specialist (JNCIS-ENT) documents and learning resources available at Juniper Networks23.

Answer : C

The exhibit shows the output of the commandshow vlans brief, which displays brief information about VLANs and their associated interfaces1.

The output has four columns: Routing instance, VLAN name, Interfaces, and Tagging.

The * symbol indicates that the interface is active, meaning that it is up and forwarding traffic1.This can be verified by the commandshow interfaces terse, which displays the status of the interfaces2.

Answer : B, C

Bis 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.

Cis 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.

Answer : A, D

On Juniper switches, the default VLAN is set to a VLAN ID of 1 by default12.This means that all interfaces on the switch are members of VLAN 1 until they are specifically assigned to another VLAN12. Therefore, option A is correct.

The default VLAN ID can be changed12.This allows network administrators to configure the switch to use a different VLAN as the default, if necessary12. Therefore, option D is correct.

Answer : B

The exhibit shows the configuration of BFD liveness detection for BGP at the global level, which applies to all BGP neighbors by default1.However, this configuration does not specify the session mode, which determines whether BFD uses single-hop or multihop mode to communicate with a neighbor2.

For single-hop BGP neighbors, which are directly connected on the same subnet, the session mode can be either automatic or single-hop.For multihop BGP neighbors, which are not directly connected and require multiple hops to reach, the session mode must be multihop2.

Since your BGP neighbors are in different countries, they are likely to be multihop neighbors.Therefore, you need to configure the session mode as multihop for each neighbor individually at the [edit protocols bgp group group-name neighbor address bfd-liveness-detection] hierarchy level2. For example:

protocols { bgp { group usa { neighbor 192.0.2.1 { bfd-liveness-detection { session-mode multihop; } } } group france { neighbor 198.51.100.1 { bfd-liveness-detection { session-mode multihop; } } } } }

If you do not configure the session mode for multihop neighbors, BFD will use the default mode of automatic, which will try to use single-hop mode and fail to establish a BFD session with the remote neighbor2. This will prevent BGP from using BFD to detect liveliness and failover.

Therefore, the answerBis correct, as you need to configure the BFD liveness detection on the BGP neighbor level with the appropriate session mode for multihop neighbors.

Answer : A, C

BGP attributes are properties that BGP uses for route advertisement, path selection, and loop prevention1.There are four categories of BGP attributes123:

Well-known mandatory: Must be recognized by all BGP routers, present in all BGP updates, and passed on to other BGP routers123.

Well-known discretionary: Supported by all BGP implementations, and are optionally included in BGP updates1.

Optional transitive: May not be supported by all implementations of BGP1.

Optional non-transitive: May not be supported by all implementations of BGP1.

The well-known mandatory attributes must be supported by all BGP implementations and must be included in every update123.These include the AS path and next hop attributes23. Therefore, options A and C are correct.

Answer : A, C

Ais correct because RSTP alternate ports block traffic while receiving superior BPDUs from a neighboring switch.An alternate port is a backup port for a root port, which means it receives better BPDUs from another bridge than the current root port1.However, an alternate port does not forward any traffic, as it is in a discarding state2. It only listens to BPDUs and waits for the root port to fail.If the root port fails, the alternate port can immediately transition to a forwarding state and become the new root port1.

Cis correct because RSTP alternate ports provide an alternate higher cost path to the root bridge.An alternate port is selected based on the same criteria as the root port, which are the lowest bridge ID, the lowest path cost, the lowest sender port ID, and the lowest receiver port ID3.However, an alternate port receives a higher cost BPDU than the root port, otherwise it would be the root port itself1. Therefore, an alternate port provides an alternate higher cost path to the root bridge than the root port.