Question 1

Regarding the BGP decision algorithm, which two statements are correct? (Choose two.)

Accepted Answer

A, C

Explanation: The Border Gateway Protocol (BGP) decision algorithm is a multi-step process used to select the single best path to a destination. A fundamental prerequisite is that the next-hop router for a path must be reachable; if the next-hop is inaccessible (i.e., no route to it exists in the Interior Gateway Protocol), the BGP path is considered invalid and is not eligible for selection. Among the valid paths, the LOCALPREF attribute is one of the first criteria evaluated. This attribute is used within an Autonomous System (AS) to influence the exit point for outbound traffic. A path with a higher LOCALPREF value is always preferred over a path with a lower value.

Question 2

What is the maximum number of unique VLAN IDs available?

Accepted Answer

C

Explanation: The maximum number of unique VLAN IDs is defined by the IEEE 802.1Q standard. The standard specifies a 12-bit field for the VLAN Identifier (VID) within the Ethernet frame's VLAN tag. A 12-bit field can represent 2^12, or 4096, unique values. This creates a theoretical range of VLAN IDs from 0 to 4095. While IDs 0 and 4095 are reserved for specific functions and are generally not usable for user-configured VLANs, the total address space defined by the 12-bit field is 4096.

Question 3

An IS-IS router has been assigned the NSAP address: 49.00F0.0100.5012.3010.00. What is the Area ID to which the router belongs?

Accepted Answer

A

Explanation: The IS-IS Network Service Access Point (NSAP) address is structured into three parts: the Area ID, the System ID, and the N-Selector (NSEL). According to the ISO/IEC 10589 standard, the NSEL is the last byte (octet), and the System ID is a fixed length of six bytes that precedes the NSEL. The remainder of the address at the beginning constitutes the Area ID. Given the address 49.00F0.0100.5012.3010.00: NSEL: 00 (the last byte) System ID: 0100.5012.3010 (the preceding six bytes) Area ID: 49.00F0 (the remaining part)

Question 4

In OSPFv2, which route characteristic is used to determine the best path?

Accepted Answer

C

Explanation: OSPF (Open Shortest Path First) is a link-state routing protocol that uses the Shortest Path First (SPF) algorithm, also known as Dijkstra's algorithm, to determine the best path to a destination. The metric used in this calculation is "cost." The cost of a path is the cumulative value of the costs assigned to each outgoing interface along the path from the source to the destination. The route with the lowest total cost is considered the best path and is installed in the IP routing table. The interface cost is typically calculated based on the interface's bandwidth, with higher bandwidth links having a lower cost.

Question 5

Which two statements are true about link-state routing protocols? (Choose two.)

Accepted Answer

A, B

Explanation: Link-state routing protocols, such as OSPF, are designed for efficiency and accuracy. They achieve this by having each router build a complete map of the network topology. Updates, known as Link-State Advertisements (LSAs), are not sent periodically but are triggered by an event, such as a link failure or a change in link cost. This makes the protocol efficient in stable networks. To ensure every router maintains an identical and accurate topology database, these updates are flooded throughout the network using a reliable transport mechanism that includes acknowledgments, ensuring all neighbors receive the information correctly.

Question 6

Review the exhibit. https://kxbjsyuhceggsyvxdkof.supabase.co/storage/v1/object/public/file-images/Ericsson_ECP-206/page_28_img_1.jpg In the exhibit, which action is performed by router R3 for traffic arriving from router R2 towards router R4?

Accepted Answer

D

Explanation: In the exhibited MPLS network, router R3 is the penultimate hop Label Switching Router (LSR) for the path ending at the egress Label Edge Router (LER), R4. The standard and most efficient operation performed by a penultimate router is Penultimate Hop Popping (PHP). With PHP, R3 removes the transport MPLS label from the packet before forwarding it to R4. This action is an optimization that reduces the processing load on the egress router (R4), as R4 receives a native IP packet and can perform a single lookup in its IP Forwarding Information Base (FIB) instead of two lookups (one in the LFIB and one in the FIB).

Question 7

Review the exhibit. https://kxbjsyuhceggsyvxdkof.supabase.co/storage/v1/object/public/file-images/Ericsson_ECP-206/page_17_img_1.jpg A service provider wants to provide L3VPN for two customers (indicated by red and green in the exhibit). Referring to the exhibit, which statement is correct?

Accepted Answer

D

Explanation: In an MPLS L3VPN architecture, the Provider (P) routers form the core of the service provider's network and are responsible for high-speed packet forwarding based on MPLS labels. They perform label switching on the transport label (outer label) to forward traffic between Provider Edge (PE) routers. P routers do not participate in the customer's routing via MP-BGP and do not maintain customer-specific routing tables (VRFs). Consequently, they have no knowledge of the customer's IP prefixes, ensuring the core remains simple, scalable, and secure.

Question 8

Which two statements are true about route summarization? (Choose two.)

Accepted Answer

A, B

Explanation: Route summarization, or route aggregation, is a core technique for improving the scalability of routing protocols. Its primary benefit is reducing the number of entries in a router's routing table by advertising a single, less-specific summary route in place of multiple, more-specific routes. This directly leads to smaller routing tables, which consume less memory and processing power. A crucial secondary benefit is enhanced network stability. By summarizing routes, individual link failures within the aggregated address block are not advertised to the rest of the network, thus reducing the volume of routing update messages (signaling) and preventing route flapping from propagating.

Question 9

Which conceptual table created by routing protocols is used when processing an IP packet?

Accepted Answer

D

Explanation: The Forwarding Information Base (FIB), also known as a forwarding table, is the specific data structure used by a router's data plane to make forwarding decisions for IP packets. While routing protocols (operating in the control plane) populate a Routing Information Base (RIB) with all known routes, the FIB is a streamlined, optimized version containing only the best, unambiguous routes. This optimization allows for the extremely fast lookups required for line-rate packet processing. When a packet arrives, its destination IP address is looked up in the FIB to determine the next-hop and egress interface.

Question 10

Which two statements are true about priority queuing (PQ)? (Choose two.)

Accepted Answer

A, C

Explanation: Priority Queuing (PQ) is a Quality of Service (QoS) scheduling algorithm that services queues based on a strict priority hierarchy. It always dequeues packets from the highest-priority queue first. As long as there are packets in the highest-priority queue, no other queue is serviced. This ensures that the most critical traffic experiences the lowest possible latency and jitter. However, a major drawback of this method is "starvation," where a continuous flow of high-priority traffic can prevent lower-priority queues from ever being serviced, denying them any bandwidth. PQ does not provide minimum bandwidth guarantees.

Question 11

Which protocol would be used to bundle multiple Ethernet ports into a virtual link with an aggregated bandwidth?

Accepted Answer

B

Explanation: The Link Aggregation Control Protocol (LACP) is the standard protocol used for the dynamic creation and management of Link Aggregation Groups (LAGs). LACP, defined in the IEEE 802.1AX standard (formerly IEEE 802.3ad), allows multiple physical Ethernet ports to be bundled together to form a single, high-bandwidth logical link. This aggregation not only increases the total available bandwidth but also provides link-level redundancy. If a physical link within the LAG fails, traffic is automatically redistributed across the remaining active links without disrupting the logical connection.

Question 12

What are two roles of the DHCP protocol in a network? (Choose two.)

Accepted Answer

A, B

Explanation: The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on IP networks for automatically assigning IP addresses and other communication parameters to devices. Its fundamental role (A) is to provide a client with a unique IP address, subnet mask, and a lease for that address. Additionally, DHCP is designed to deliver other critical configuration options, including the IP address of the default gateway (B), which enables the host to communicate with devices outside its local subnet. It also commonly provides DNS server addresses.

Question 13

Which statement is true about LDP?

Accepted Answer

C

Explanation: The Label Distribution Protocol (LDP) is a signaling protocol, not a routing protocol. Its primary function is to advertise and distribute MPLS labels for Forwarding Equivalence Classes (FECs). To determine the path for a Label Switched Path (LSP), LDP consults the IP Routing Information Base (RIB), which is populated by an Interior Gateway Protocol (IGP) like OSPF or IS-IS. LDP binds labels to prefixes learned from the IGP and uses the IGP's next-hop information to forward labeled packets. Therefore, LDP is entirely dependent on the IGP for path calculation and all routing-related decisions.

Question 14

What is a label-edged router (LER)?

Accepted Answer

C

Explanation: A Label Edge Router (LER) is a router that operates at the boundary of an MPLS network. Its primary functions are to classify incoming IP packets into Forwarding Equivalence Classes (FECs), push a label onto them as they enter the MPLS domain (ingress LER), and pop the label as they exit the domain (egress LER). This role is precisely fulfilled by a Provider Edge (PE) router, which serves as the gateway between a customer's network (connected via a CE router) and the provider's MPLS core. The PE router handles the critical label imposition and disposition operations that define the edge of the label-switched path.

Question 15

A network operator wants to make sure voice data is prioritized. In this scenario, to which Ethernet traffic class should it be assigned.

Accepted Answer

D

Explanation: The IEEE 802.1p standard, part of the IEEE 802.1Q specification for VLAN tagging, defines a 3-bit Priority Code Point (PCP) field to enable Quality of Service (QoS) at the MAC layer. This field allows for eight traffic classes (0-7). According to standard recommendations, traffic class 6 is designated for voice traffic. This class is engineered for applications with very low latency and jitter requirements (typically <10 ms), ensuring that real-time voice packets are prioritized over other types of data, such as video (class 5) or best-effort traffic (class 0), to maintain high-quality communication.

Free Ericsson ECP-206 IP Networking Actual Exam Questions