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 adjacency 1 .

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 adjacency 1 .

These explanations are based on the Enterprise Routing and Switching Specialist (JNCIS-ENT) documents and learning resources available at Juniper Networks 2 3 .

The exhibit shows the output of the command  show vlans brief , which displays brief information about VLANs and their associated interfaces 1 .

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 traffic 1 .  This can be verified by the command  show interfaces terse , which displays the status of the interfaces 2 .

According to the Juniper documentation1, a native VLAN is a VLAN that carries untagged traffic on a trunk port. A Wi-Fi access point may need a native VLAN to associate untagged traffic with a specific VLAN, such as the management VLAN. On Juniper EX Series switches, you can enable a native VLAN on a switch port by setting the interface-mode to trunk and specifying a native-vlan-id. For example, the following configuration enables a native VLAN with ID 1 on the switch port ge-0/0/12:

set interfaces ge-0/0/1 unit 0 family ethernet-switching interface-mode trunk

set interfaces ge-0/0/1 unit 0 family ethernet-switching vlan members all

set interfaces ge-0/0/1 unit 0 family ethernet-switching native-vlan-id 1

The other options are not correct because they do not address the requirement of untagged traffic. VLAN tagging is the process of adding a VLAN identifier to a frame, which is not needed for untagged traffic. Flexible VLAN tagging is a feature that allows multiple VLAN tags on a single interface, which is not relevant for this scenario. Voice VLAN is a feature that allows voice traffic to be separated from data traffic on a switch port, which is not related to untagged traffic or Wi-Fi access points. References: Understanding Native VLANs on Trunks | Junos OS, Configuring a Native VLAN on a Trunk Port | Junos OS