Junos OS 24.4 on EX Series switches provides robust support for LLDP (Link Layer Discovery Protocol) and its extension,LLDP-MED(Media Endpoint Discovery).
* LLDP-MED Power Negotiation:This feature allows a switch (Power Sourcing Equipment or PSE) and a connected device (Powered Device or PD), such as an IP phone or access point, to negotiate power requirements beyond the standard IEEE 802.3af/at classes. The switch candynamically allocate the exact amount of power the device needs (in 0.1W increments), which optimizes the power budget of the switch.
* LLDP Scope:LLDP is a Link Layer protocol (Layer 2), but it is not restricted to Layer 2 interfaces; it can also operate onLayer 3 interfacesto advertise system identity and capabilities. This makesOption A incorrect.
* Link-Local Protocol:LLDP frames use a specific multicast MAC address (01:80:c2:00:00:0e) that is not floodedor forwarded by switches. They are strictly link-local between two directly connected neighbors. This makesOption Bincorrect.
* Endpoint Focus:LLDP-MED is specifically designed forMedia Endpoint Devices(like VoIP phones), providing TLVs for network policy (VLAN/QoS), location identification, and inventory management.
Standard LLDP is used for discovering network connectivity devices. This makesOption Dincorrect.

To simplify VLAN management and automate the creation and pruning of VLANs across a network, Juniper utilizes theMultiple VLAN Registration Protocol (MVRP).
* MVRP on Trunk Interfaces (Option C):MVRP is the IEEE 802.1ak standard that replaces the older, proprietary GVRP. It is designed to run ontrunk interfacesbetween switches.
* Dynamic Creation:When a VLAN is added to one switch, MVRP advertises its existence to neighboring switches. If those switches need to reach that VLAN, they can dynamically create it in their database.
* Pruning:If a switch no longer has any active ports or downstream neighbors interested in a specific VLAN, it stops advertising that VLAN on its trunks. This "prunes" the VLAN traffic from those links, saving bandwidth.
* Incorrect Options:Option A and Bare incorrect because GVRP is legacy and no longer the recommended protocol for modern Junos deployments.Option Dis incorrect because MVRP is meant for inter-switch trunk links to manage the fabric, not for edge access ports where VLAN membership is usually static.

In Junos OS Class of Service (CoS),schedulersare the components that define how traffic in a specific queue is treated before it is transmitted out of an interface.
* Queue Priority (Statement C):A scheduler identifies thepriorityof the queue (e.g., low, medium-low, medium-high, or high). This determines the order in which the hardware handles traffic from different queues.
* Buffer Size (Statement D):A scheduler defines thebuffer size(amount of memory) allocated to a queue, which can be specified as a percentage, a temporal value (in microseconds), or the remainder of available buffer space. This helps manage bursts of traffic and prevent tail drops.
* Other Components:Rate-limiting (Statement A) is typically handled bypolicersor interface-level shaping, while code translation (Statement B) is the role ofrewrite rules.

Junos OS 24.4 provides several server-failover options for 802.1X authentication to maintain network availability when the RADIUS server is unreachable.
* Fallback Behavior (Option D):Theuse-cachefallback action allows the switch to consult its local cache of previously authenticated MAC addresses.
* If a device was already authorized and its information is in the cache, the switch willcontinue to permit accessbased on those cached credentials.
* However, if a new device (not in the cache) attempts to connect while the server is down, the switch cannot verify its credentials and willdeny the access attempt. This matches the specific requirement to permit authorized devices while denying new ones.
* Other Fallback Options:
* permit (Option C):This would allowalldevices (even new ones) to access the network, typically in a restricted "guest" or "bypass" VLAN.
* deny (Option A):This would drop all traffic from all devices on the port if the server is unreachable.
* vlan-name (Option B):This moves authenticated or unauthenticated users into a specific fallback VLAN.

To provide IP phones with geographic location details (such as civic addresses or coordinates) automatically, Juniper EX Series switches utilize theLLDP-MED (Link Layer Discovery Protocol - Media Endpoint Discovery)protocol.
* VoIP Specifics:While standard LLDP (C) is for general device discovery,LLDP-MEDis an enhancement specifically designed for network-to-endpoint communication for VoIP devices.
* Location Identification:LLDP-MED supportsLocation Identification TLVs(Type-Length-Values).
These allow a switch to push geographic or civic location data to an IP phone, which is critical for E911 services and asset tracking.
* Junos Implementation:On EX Series switches, this is typically configured under protocols lldp-med to ensure the switch advertises the necessary location information to connected endpoints.