ECP-206 Free Exam Questions & Answers PDF Updated on Mar-2024 [Q25-Q40]

Explanation
Penultimate hop popping (PHP) is a function performed by certain routers in an MPLS enabled network. It refers to the process whereby the outermost label of an MPLS tagged packet is removed by a label switch router (LSR) before the packet is passed to an adjacent label edge router (LER). The purpose of PHP is to reduce the load on the LER, as it saves one cycle of label lookup. The LER can forward the packet based on its IP header or another label in the stack, without having to process the outer label. PHPfunctionality is achieved by the LER advertising a label with a value of 3 to its neighbors. This label is defined as “implicit-null” and informs the neighboring LSRs to perform PHP12.
References: Penultimate hop popping – Wikipedia, MPLS Penultimate hop popping – NetworkLessons.com

Explanation
Referring to the exhibit, the two Ericsson routers that support the 100GE interface are Router 6675 and Router
6672. The 100GE interface is a high-speed Ethernet interface that operates at 100 gigabits per second. The Ericsson Router 6000 series is a family ofrouters that provide IP transport for mobile and fixed networks. The Router 6675 is a 5G combined access and E-RAN switch with 100GE interfaces and 320Gb forwarding capacity. The Router 6672 is a high-capacity metro aggregation router with 100GE interfaces and 1.6Tb forwarding capacity12.
References: Router 6000 Series – Ericsson, New Ericsson Router 6000 series couples radio and IP transport for
5G future – Global Brands Magazine

Explanation
A reason for using VLANs in an IP network is to isolate hosts within the same IP subnet. VLANs (Virtual LANs) are logical grouping of devices in the same broadcast domain. VLANs are usually configured on switches by placing some interfaces into one broadcast domain and some interfaces into another. Each VLAN acts as a subgroup of the switch ports in an Ethernet LAN. VLANs allow network administrators to group hosts together even if the hosts are not directly connected to the same network switch. By using VLANs, hosts within the same IP subnet can be separated into different broadcast domains, which enhances security, reduces network congestion, and simplifies network management78.
References: 8 Different Types of VLANs in TCP/IP Networks, What is a VLAN? – Study-CCNA

Explanation
OSPF runs directly on IP, while IS-IS runs directly on Ethernet. This means that OSPF uses IP addresses to identify routers and links, while IS-IS uses MAC addresses or other link-layer identifiers. OSPF also requires an IP header for each packet, while IS-IS does not. Both OSPF and IS-IS are link state protocols, which means that they flood information about the network topology to all routers in the same area or domain. References: Ericsson IP Networking – Routing Protocols, Ericsson Router 6000 Series – Ericsson

Explanation
In the exhibit, the action performed by router R3 for traffic arriving from router R2 towards router R4 is PHP, which stands for penultimate hop popping. PHP is a process in which the penultimate hop router (the router before the egress router) removes the top label from an MPLS packet before forwarding it to the egress router.
This reduces the label stack depth of the packet and relieves the egress router from performing a label lookup operation. In the exhibit, router R3 is the penultimate hop for traffic arriving from router R2 towards router R4. Router R3 will perform a PHP operation, removing the top label from the incoming packet before forwarding it to router R478.
References: PHP Tutorial – W3Schools, PHP: Downloads

Explanation
Two protocols that apply to both IPv4 and IPv6 are:
SNMP: This stands for Simple Network Management Protocol, which is a protocol that allows network administrators to monitor and manage network devices such as routers, switches, servers, printers, etc.
SNMP uses a client-server model, where an SNMP manager (client) can query or configure an SNMP agent (server) on a network device using SNMP messages. SNMP can operate over both IPv4 and IPv6 networks56.
DNS: This stands for Domain Name System, which is a protocol that translates human-readable domain names (such as www.example.com) into numerical IPaddresses (such as 192.0.2.1 or 2001:db8::1) that identify network devices. DNS uses a hierarchical distributed database of name servers that store and resolve domain names and IP addresses. DNS can support both IPv4 and IPv6 addresses78.
References: Simple Network Management Protocol – Wikipedia, SNMP over IPv6 – Cisco, Domain Name System – Wikipedia, DNS for IPv6 – Cisco

Explanation
The protocol that would be used to bundle multiple Ethernet ports into a virtual link with an aggregated bandwidth is LACP, which stands for Link Aggregation Control Protocol. LACP is a protocol that allows two or more devices to negotiate the formation of a link aggregation group (LAG), also known as an EtherChannel or a port channel. A LAG combines multiple physical links into one logical link that provides increased bandwidth, load balancing, and redundancy. LACP is defined in IEEE 802.3ad and 802.1AX standards12.
References: Link Aggregation Control Protocol – Wikipedia, What is “link aggregation” and how does it benefit your network? | PC Gamer

Explanation
An LDP implicit null label causes penultimate hop popping by a downstream router. LDP is a protocol that distributes labels for MPLS forwarding along the shortest path calculated by an IGP. An implicit null label is a special label value of 3 that indicates that the downstream router does not need a label to forward the packet to its destination. When an upstream router receives an implicit null label from a downstream router, it removes (or pops) the label from the packet before sending it to the downstream router. This process is called penultimate hop popping (PHP) and it reduces the load on the downstream router, which can forward the packet based on its IP header or another label in the stack59.
References: MPLS Label Distribution Protocol Commands – Cisco, Solved: Implicit null and Explicit null – Cisco Community

Explanation
IPv6 link-local addresses are designed to be used in three situations: for neighbor discovery, for local IP communication on the IPv6 capable routers, and for addressing on a single link for purposes such as auto-address configuration. Neighbor discovery is a protocol that allows IPv6 nodes to discover each other and learn their link-layer addresses on a local network. Neighbor discovery uses link-local addresses to send and receive messages such as router advertisements, router solicitations, neighbor advertisements, and neighbor solicitations34. Local IP communication on the IPv6 capable routers refers to the ability of routers to exchange routing information or management traffic using their link-local addresses as source and destination addresses. This reduces the need for global unicast addresses on router interfaces that are not reachable from outside the local network35. Addressing on a single link for purposes such as auto-address configuration refers to the use of link-local addresses to enable IPv6 nodes to obtain an address without manual configuration or a DHCP server. Link-local addresses can be automatically derived from the interface identifier in the modified EUI-64 format or randomly generated. Link-local addresses can also be used to test the connectivity of a link before obtaining a global unicast address36.
References: Understand the IPv6 Link-Local Address – Cisco, Link Local Address – GeeksforGeeks, IPv6 Address Types | Link-Local, Global Unicast, etc. IPCisco, MPLS Label Distribution Protocol Commands – Cisco

Explanation
Route summarization is a technique that reduces the number of routes that a router advertises to its neighbors by creating a single summary route that covers multiple subnets or networks. Route summarization has several benefits, such as:
It reduces the size of a routing table, which saves memory and CPU resources on the router. A smaller routing table also improves the lookup efficiency and convergence time of the routing protocol.
It reduces signaling, which means that less bandwidth is consumed by routing updates and less processing is required by neighboring routers. This also enhances the stability and scalability of the network, as fewer routing changes are propagated.
It improves route aggregation, which means that more specific routes are replaced by a less specific route that can be advertised to other autonomous systems or routing domains. This simplifies the inter-domain routing and hides the internal topology details.
Route summarization does not necessarily summarize the routing table entries into a default route, although a default route can be considered a special case of route summarization where all destinations are covered by one route. Route summarization also does not improve the best route calculation, as it may introduce suboptimal routing or black holes if not done properly. : Introduction to Route Summarization – NetworkLessons.com, Route Summarization > Example for Understanding Route Summarization – Cisco Press

Explanation
The correct ordering (outer to inner) of packet headers in an IP/MPLS packet is Ethernet, MPLS, IP. An IP/MPLS packet is a packet that is encapsulated with an MPLS label stack between the Ethernet header and the IP header. The Ethernet header contains the source and destination MAC addresses and the EtherType field that indicates the type of the payload. The MPLS label stack contains one or more labels that are used for forwarding decisions by the MPLS routers. Each label consists of four fields: label value, experimental bits, bottom of stack, and time to live. The IP header contains the source and destination IP addresses and other information for routing and fragmentation. The order of the headers is important because it determines how the packet is processed by different devices in the network12.
References: MPLS Label Stack – Cisco, MPLS Fundamentals: 3 – MPLS Packet Forwarding

Explanation
In OSPFv2, the route characteristic that is used to determine the best path is the cost. The cost is a metric that represents the link bandwidth, delay, reliability, or other factors. The cost is inversely proportional to the bandwidth, meaning that a higher bandwidth link has a lower cost. The cost of a route is calculated by adding the costs of all links along the path. OSPFv2 uses the following formula to calculate the cost of an interface:
Cost = Reference bandwidth / Interface bandwidth in bps
The reference bandwidth is a constant value that can be configured by the network administrator. By default, it is 100 Mbps. The interface bandwidth is the actual bandwidth of the interface in bits per second. For example, if an interface has a bandwidth of 10 Mbps, its cost would be 100 Mbps / 10 Mbps = 101415.
OSPFv2 does not use jitter, packet loss, or delay as route characteristics to determine the best path. Jitter is the variation in latency or delay between packets. Packet loss is the percentage of packets that are dropped or corrupted during transmission. Delay is the time it takes for a packet to travel from source to destination. These characteristics are not part of the OSPFv2 protocol and are not advertised in OSPFv2 LSAs1617.
References: OSPF Metric cost Calculation Formula Explained – ComputerNetworkingNotes, OSPF Cost – OSPF Routing Protocol Metric Explained – Study-CCNA, Open Shortest Path First – Wikipedia, OSPF Metric
= Cost – Cisco

Explanation
The next-hop to reach the host 192.168.1.129 is 10.126.131.250. This can be determined by looking at the routing table in the exhibit. The host 192.168.1.129 falls within the range of the network 192.168.1.64/26, which has a next-hop of 10.126.131.250. References: Ericsson IP Networking – IP Addressing, Software Installation and Upgrade Overview (Junos OS)

Explanation
The subnet address for 10.57.126.156/29 is 10.57.126.152. To find the subnet address, we need to perform a bitwise AND operation between the IP address and the subnet mask. The subnet mask for /29 is
255.255.255.248, which in binary is 11111111.11111111.11111111.11111000. The IP address in binary is
00001010.00111001.01111110.10011100. The result of the AND operation is
00001010.00111001.01111110.10011000, which in decimal is10.57.126.152. References: Ericsson IP Networking – IP Addressing, Software Installation and Upgrade Overview (Junos OS)

Explanation
IPsec provides two main features: protecting packets from modification and hiding the content of packets from observation. IPsec protects packets from modification by using cryptographic algorithms to generate and verify message authentication codes (MACs) or digital signatures for each packet. These mechanisms ensure that the packets have not been tampered with or altered in transit by unauthorized parties. IPsec hides the content of packets from observation by using encryption algorithms to scramble the payload of each packet. This prevents eavesdroppers or interceptors from reading or analyzing the data carried by the packets12.
References: What is IPsec? | How IPsec VPNs work | Cloudflare, IPsec – Wikipedia

Explanation
The operating system used in Ericsson Router 6000 products is ERS (Ericsson Router Software). ERS is based on IPOS (IP Operating System), which is a common operating system for Ericsson’s IP portfolio. ERS provides advanced features and functionality for IP transport, such as MPLS, Segment Routing, QoS, IPSec, synchronization, SDN, and more. ERS also supports seamless integration with Ericsson Radio System and Ericsson Network Manager.
References: Router 6000 Series – Ericsson, Router 6675 Datasheet – Winncom