Nokia 4A0-100 Exam Dumps

Spanning Tree Protocol (STP) is used specifically in Ethernet Layer 2 networks to prevent loops caused by redundant paths.

STP detects loops and blocks one or more redundant paths to ensure there is a loop-free topology in a bridged network.

STP dynamically recalculates the topology if a link fails, reactivating previously blocked paths.

Explanation of other options:

A . MPLS with LSPs: MPLS uses its own mechanisms for path management, such as RSVP or Segment Routing. STP is not applicable here.

C . OSPF with ECMP (Equal-Cost Multi-Path): OSPF is a Layer 3 protocol that inherently supports multiple paths without loops; STP is not involved.

D . eBGP (Exterior Border Gateway Protocol): Operates at Layer 3 for inter-AS communication; STP is not used in BGP routing.

Therefore, Option B is correct, as STP is explicitly designed for Layer 2 Ethernet networks with redundant paths.

Nokia IP Networking Fundamentals Study Guide -- Chapter: 'Layer 2 Technologies'

IEEE 802.1D Standard -- Spanning Tree Protocol Overview

A Virtual Local Area Network (VLAN) is a logical separation of devices at Layer 2, even if those devices are connected to the same physical switch. Each VLAN forms its own broadcast domain, and traffic cannot cross from one VLAN to another without Layer 3 routing.

Option A is incorrect -- devices on the same switch but in different VLANs still cannot communicate directly.

Option B is incorrect -- VLANs explicitly create separate broadcast domains.

Option D is technically incorrect -- communication is possible with the right setup.

Option C is correct -- to enable communication between different VLANs, a router or a Layer 3 switch with inter-VLAN routing capability is required.

This process is called inter-VLAN routing, and it's a fundamental task in enterprise networks using VLANs.

Nokia IP Networking Fundamentals Study Guide -- Chapter: 'LAN Segmentation and VLANs'

Cisco CCNA and CompTIA Network+ -- Inter-VLAN Routing Concepts

A VPRN (Virtual Private Routed Network) provides a Layer 3 VPN service over a service provider's network.

Each customer site connects to a PE router.

Sites are connected via a routed network using separate routing instances.

Customer routers see routed connectivity, as if connected to their own private WAN.

Option C is correct -- VPRN provides routed connectivity between sites.

Nokia Service Routing Guide -- Chapter: VPRN

Nokia SRA Guide -- Service Types and Operation

The Shortest Path Tree (SPT) is calculated by Link-State routing protocols like OSPF and IS-IS using:

A complete map of the network topology.

Each router uses algorithms like Dijkstra's to compute the shortest paths to all destinations.

Option C is correct -- full network topology is used.

Option A refers to Distance Vector methods.

Option B and D are results of topology analysis but not the input used.

Nokia Routing Protocols Guide -- Section: ''SPT and Link-State Behavior''

RFC 2328 -- OSPF Specification

A /31 subnet in IPv4 provides exactly two IP addresses (e.g., 192.168.1.0/31 usable: 192.168.1.0 and 192.168.1.1). Traditionally, these would represent a network address and a broadcast address, but RFC 3021 redefines /31 subnets for point-to-point links, such as router-to-router connections.

In a /31 subnet:

Broadcast address is not used.

Both IPs are treated as usable host addresses.

It's ideal for point-to-point links, saving address space.

This is widely supported and standardized in Nokia IP and routing platforms.

Nokia IP Fundamentals Guide -- Subnetting Techniques

RFC 3021 -- 'Using 31-Bit Prefixes on IPv4 Point-to-Point Links'