BGP (Border Gateway Protocol)uses amulti-step decision processto select the best route among multiple paths. It doesnot use SPF or simple metrics like hop count.

Key BGP selection criteria include:

Local preference

AS path length

Origin type

MED (Multi-Exit Discriminator)

eBGP over iBGP

IGP metric to next hop

Option C is correct– BGP evaluatesmultiple attributesfor route selection.

TheNokia 7750 SR architectureseparates its operations intocontrol planeanddata planefunctions.

TheData Planeincludes hardware components responsible for forwarding traffic at line rate. These components include:

MDA (Media Dependent Adapter)– interfaces with physical media.

IOM (Input/Output Module)– performs high-speed packet forwarding and processing.

XMA (eXpandable Media Adapter)– extends port capacity and media support.

TheControl Planeincludes theCPM (Control Processor Module), which is responsible for running routing protocols, managing configuration, system operations, and other control-related functions. The CPM does not participate in data forwarding and is thusnot part of the data plane.

Spanning Tree Protocol (STP)is used specifically inEthernet Layer 2 networkstoprevent loopscaused byredundant paths.

STPdetects loops and blocks one or more redundant pathsto ensure there is aloop-free topologyin a bridged network.

STP dynamicallyrecalculates the topologyif 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 Bis correct, as STP is explicitly designed forLayer 2 Ethernet networkswithredundant paths.

AVPRN (Virtual Private Routed Network)provides aLayer 3 VPN serviceover a service provider’s network.

Each customer site connects to aPE router.

Sites are connected via arouted networkusingseparate routing instances.

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

Option C is correct– VPRN providesrouted connectivitybetween sites.

Thesystem interfacein Nokia SR OS is aloopback-style logical interfacethat represents therouter itself. It is used for:

Router ID assignment (if not manually set)

Source IP for control-plane protocols (OSPF, BGP)

Reachability testing

Important properties:

It istype loopback✔

Itexists by default✔

If router ID is unset, it uses thesystem IP address✔

Butthe IP address on the system interfacedoes not need to be /32❌

It can haveother prefix lengths, especially in service provider scenarios.

Thus, Option B is FALSE.

In Nokia SR OS:

Aphysical interfacerefers to a physical port on the router (e.g., port 1/1/1).

It can be configured withIP addresses, associated with services (e.g., IES, VPRN), and connects to other routers or customer devices.

Systemandloopbackinterfaces arelogical interfaces, not physical.

Option D is FALSE, because a physical interfacecannotbe of type "system" or "loopback" — those arevirtual/logicalinterfaces in the Nokia router architecture.

TheShortest Path Tree (SPT)is calculated byLink-State routing protocolslikeOSPFandIS-ISusing:

Acomplete map of the network topology.

Each router uses algorithms likeDijkstra’sto compute the shortest paths to all destinations.

Option C is correct– fullnetwork topologyis used.

Option Arefers to Distance Vector methods.

Option BandDare results of topology analysis but not the input used.

On theNokia 7750 SR, theControl Processor Module (CPM)includes two compact flash slots,CF1 and CF2, which are used for storing crucial system files. These include:

Runtime software image

Configuration files

Logs and backup configurations

BothCF1 and CF2are used for redundancy and flexibility. Typically, CF1 is designated as the primary storage location for the active software image and configuration, while CF2 serves as a backup. In some configurations, the router can boot from either CF1 or CF2 depending on system settings and availability.

This redundancy is essential for high availability and fast recovery in the event of a failure or manual software update.

TheIngress Label Edge Router (LER)is the first router that:

Receives an unlabeled IP packet.

Applies an MPLS labelbased on its forwarding decision.

Forwards it into theMPLS core.

Option A is correct– Ingress LER does MPLS label push.

Option B (Egress LER)– removes labels at the end of the path.

Option C (LSR)– switches labels, but doesn’t push them onto unlabeled packets.

Option D– is not a specific MPLS role.