On MX Series devices, MAC learning is a function of a bridge domain. To disable MAC learning for a specific logical interface, the no-mac-learning statement must be applied to that interface within the bridge domain's configuration hierarchy. The correct syntax is set bridge-domains interface no-mac-learning. Option B correctly applies this configuration, targeting only the ge-0/0/0.0 interface within the data bridge domain, fulfilling the specific requirement of the question.

A. This syntax is incorrect. The no-mac-learning statement is not a valid option directly under the [edit interfaces ge-0/0/0 unit 0] hierarchy.

C. This command disables MAC learning for the entire data bridge domain, affecting all interfaces within it, not just the specified ge-0/0/0.0 interface.

D. This syntax is incorrect. The no-mac-learning statement cannot be applied to a physical interface (ge-0/0/0) at this configuration hierarchy.

1. Juniper Networks TechLibrary, Junos OS 22.4R1. Layer 2 Configuration Guide. "Disabling MAC Learning for a Logical Interface in a Bridge Domain". This document explicitly shows the correct configuration method: [edit bridge-domains data] user@host# set interface ge-1/0/1.0 no-mac-learning, which is the command structure presented in Option B.

2. Juniper Networks TechLibrary, Junos OS 22.4R1. CLI Explorer. no-mac-learning (Bridge Domains). This reference details the statement's usage, specifying it can be configured at the [edit bridge-domains bridge-domain-name] level for the entire domain or at the [edit bridge-domains bridge-domain-name interface interface-name] level for a specific interface. This confirms the validity of Option B's syntax and the invalidity of Option C for the given scenario.

The Explicit Route Object (ERO) is used in RSVP Path messages to specify a particular path that a Label-Switched Path (LSP) must take. The ingress Label Switching Router (LSR) includes the ERO, which contains a list of specific routers (hops) for the path. This allows network administrators to explicitly control the route, overriding the path that would otherwise be selected by the Interior Gateway Protocol (IGP). This capability is fundamental to MPLS Traffic Engineering (TE).

A. The record route object (RRO) is used to record the actual path that an LSP traverses, not to influence its selection beforehand.

C. The hop object (PHOP/NHOP) identifies the previous or next hop router in the path for message processing, but does not define the entire explicit route.

D. The session object identifies the specific data flow (e.g., destination address, protocol) for which a reservation is being made, not the network path.

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1. Juniper Networks TechLibrary, MPLS Applications User Guide, "RSVP Traffic Engineering." This guide states, "To establish a TE LSP, the ingress router must determine the path to the egress router. The path can be explicit. An explicit path is a list of routers, specified in the ERO, that the LSP must traverse." This directly links the ERO to path selection.

2. Juniper Networks TechLibrary, Junos OS Routing Protocols Library for Routing Devices, "RSVP Objects." This document defines the key RSVP objects. It describes the Explicit Route Object (ERO) as being "carried in Path messages. It consists of a sequence of hops that the LSP must traverse." It also defines the Record Route Object (RRO) as being used to "record the actual route taken by the LSP," clearly distinguishing its function from the ERO.

3. Juniper Networks Day One, "This Week: An Expert Packet Walkthrough on the Junos OS," Chapter 4: MPLS. This book explains, "The ingress LER will insert an Explicit Route Object (ERO) into the RSVP Path message... The ERO contains the list of hops that the LSP must traverse." This reinforces the ERO's role in dictating the path.

When a packet matches a static route configured with the reject next-hop action, the Junos device performs two actions: it drops the packet and sends an ICMP "Destination Unreachable" message back to the source host. This behavior explicitly informs the source that the destination is unreachable, which is distinct from the discard action that drops the packet silently without any notification. The reject option is commonly used to enforce routing policies and provide immediate feedback about unreachable networks.

A. The system silently drops the packet.

This describes the discard next-hop action, not reject. Reject actively sends an ICMP notification.

B. An ICMP message is sent to the source and the packet is forwarded.

This is incorrect because the primary function of the reject action is to stop the packet from being forwarded.

D. The packet is forwarded and the packet is marked as rejected in the header.

This is incorrect. The packet is dropped, not forwarded, and there is no standard mechanism to "mark" a packet as rejected in its header for forwarding.

1. Juniper Networks TechLibrary, Junos OS Routing Protocols Library for Routing Devices: In the section describing static routing options, the reject next-hop is defined. It states, "If the routing device receives a packet for which the destination address matches a route that has reject as the next hop, the routing device drops (discards) the packet and sends an ICMP destination unreachable message to the source."

Source: Junos OS Routing Protocols Library for Routing Devices, "Static Route Options" section.

2. Juniper Networks TechLibrary, static (Protocols) Configuration Statement: The configuration guide for static routes explicitly lists the possible next-hop actions.

Source: static (Protocols) Statement Reference, under [edit routing-options static route destination-prefix]. The documentation for the reject option specifies: "Reject the packet and send an ICMP unreachable message."

Bridge Protocol Data Units (BPDUs) are the control messages exchanged between switches running Spanning Tree Protocol (STP). Their primary purpose is to build a loop-free logical topology. This is achieved through two main functions: first, switches use the Bridge ID information within BPDUs to elect a single root bridge for the entire Layer 2 domain. Second, after the root bridge is elected, switches use the path cost information contained in BPDUs to calculate and determine the shortest (least-cost) path to that root bridge. These two functions are fundamental to establishing the stable, loop-free spanning tree.

A. to exchange MAC addresses: General MAC address learning for forwarding data frames occurs by inspecting the source address of incoming data traffic, not through STP BPDUs.

C. to determine the root-alternate port: The designation of a port as root-alternate (a role in RSTP) is a result of the BPDU exchange and path cost calculations, not the primary purpose of the BPDU message itself.

1. Juniper Networks TechLibrary, Junos OS Documentation. "Understanding Spanning Tree Protocol". In the section "STP Operation," it states, "To establish a loop-free network, STP uses a special data packet called a bridge protocol data unit (BPDU). Switches exchange BPDUs to elect a root bridge and to identify the status of ports that will be used to communicate with the root bridge." This directly supports the election of the root bridge (D) and the process of finding the best path to it (B).

2. Juniper Networks TechLibrary, Junos OS Documentation. "Understanding BPDU Protection for Spanning-Tree Protocols". The document's overview explains, "Spanning-tree protocols use special data frames called bridge protocol data units (BPDUs) to exchange information about bridge IDs and root path costs." This explicitly links BPDUs to the two core components: determining the root bridge (via bridge IDs) and determining the least-cost path (via root path costs).

3. Stanford University, CS 144: Introduction to Computer Networking. "Lecture 6: Switching". In the section on "Spanning Tree Algorithm," the lecture notes detail the contents of a BPDU: "Each BPDU contains: ID of switch sending it, ID of what sender thinks is root, Distance (cost) from sender to root." This confirms that BPDUs carry the necessary information to both determine the root bridge (D) and the least-cost path (B).

The core requirement is to control the specific path an MPLS Label Switched Path (LSP) takes through the network. This capability is known as explicit path routing or constrained-path routing, a fundamental component of MPLS Traffic Engineering (TE). The Resource Reservation Protocol (RSVP) is the signaling protocol designed for this purpose. By implementing RSVP and defining an explicit path (a list of specific router addresses), an administrator can force the LSP to traverse a predetermined route, overriding the default shortest path calculated by the Interior Gateway Protocol (IGP). The Label Distribution Protocol (LDP) does not support this functionality; it is designed to establish LSPs that strictly follow the IGP's best path.

A: Fast Reroute is a resiliency feature that provides a pre-computed backup path; it does not define the primary explicit path for the LSP.

C: The Label Distribution Protocol (LDP) lacks the capability for explicit path routing; it automatically follows the shortest path determined by the IGP.

D: LDP does not have traffic engineering extensions for defining explicit routes. This functionality is a key feature of RSVP-TE, not LDP.

1. Juniper Networks TechLibrary, Junos OS 22.4, MPLS Applications Configuration Guide. In the section "Configuring Constrained-Path LSPs," the documentation states, "To configure a constrained-path LSP, you must enable MPLS and RSVP on the router... An explicitly defined path consists of a sequence of router addresses." This directly confirms that RSVP is used to establish an LSP with a defined, explicit route.

2. Juniper Networks TechLibrary, Junos OS 22.4, MPLS Path Selection. This document clarifies the difference between the protocols: "LDP directs traffic by forwarding packets along the best path to the destination, as determined by the IGP." In contrast, for RSVP, it states, "You can configure LSPs that are explicitly routed. An explicitly routed LSP is one for which you manually specify the path the LSP should take." This highlights why LDP (options C and D) is incorrect for this scenario.

3. Juniper Networks Day One Library, "This Week: An Expert Packet Walkthrough of LDP and RSVP." In the "RSVP-TE" section, it explains, "RSVP-TE allows for the creation of explicitly routed LSPs, where the path is defined by the network administrator rather than being determined by the IGP." This reinforces that RSVP is the correct protocol for meeting the requirement.