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Question 81

Which protocol is commonly used to provide secure remote CLI access to a service provider router?

1. Telnet
2. FTP
3. SSH
4. TFTP

Correct Answer: 3

Explanation

Secure Shell (SSH) provides encrypted remote CLI access to network devices. It protects management traffic, including authentication credentials and commands, from being transmitted in clear text. Service provider administrators commonly use SSH to securely access routers for configuration, troubleshooting, and operational tasks. Telnet provides remote CLI access but does not encrypt the session. FTP and TFTP are primarily file-transfer protocols rather than interactive secure management protocols. SSH can also support features such as public-key authentication and secure file transfer through related protocols. Therefore, SSH is the correct choice for secure remote CLI management.

Question 82

Which security technology is commonly used to encrypt IP traffic between network endpoints?

1. IPsec
2. LDP
3. BFD
4. OSPF

Correct Answer: 1

Explanation

IPsec is a suite of protocols and technologies used to secure IP communications through authentication, integrity protection, and encryption. It can be used to create secure tunnels between network endpoints or sites. IPsec is commonly associated with VPN implementations where traffic must be protected while traversing an untrusted network. LDP distributes MPLS labels, BFD provides fast failure detection, and OSPF is an interior gateway routing protocol. IPsec therefore addresses confidentiality and integrity of IP traffic rather than routing or label distribution. Consequently, IPsec is the correct answer.

Question 83

Which IPsec protocol provides encryption and integrity protection for IP packets?

1. ARP
2. ESP
3. ICMP
4. DHCP

Correct Answer: 2

Explanation

Encapsulating Security Payload (ESP) is an IPsec protocol that can provide confidentiality through encryption as well as integrity and authentication protection. ESP is widely used in IPsec VPN implementations to protect traffic between endpoints. Authentication Header (AH) can provide authentication and integrity but does not provide encryption. ARP is used for IPv4 address resolution, ICMP provides control and diagnostic messaging, and DHCP provides address configuration. Therefore, ESP is the correct answer when encryption and integrity protection are required in an IPsec implementation.

Question 84

Which IPsec component is responsible for authenticating and protecting the integrity of an IP packet without providing encryption?

1. ESP
2. GRE
3. AH
4. LDP

Correct Answer: 3

Explanation

Authentication Header (AH) is an IPsec protocol that provides authentication and integrity protection but does not encrypt the payload. It can help verify that packets originated from an authenticated source and were not modified in transit. Encapsulating Security Payload (ESP), on the other hand, can provide encryption in addition to authentication and integrity features. GRE is a tunneling protocol and LDP is associated with MPLS label distribution. Therefore, AH is the correct answer when the requirement is integrity and authentication without encryption.

Question 85

Which protocol is commonly used to securely transfer files between network devices over an SSH-based connection?

1. SCP
2. TFTP
3. FTP
4. HTTP

Correct Answer: 1

Explanation

Secure Copy Protocol (SCP) provides secure file transfer using SSH. It can be used to copy configuration files, software images, logs, and other files between systems while protecting the transfer through encryption. TFTP is simple and does not provide encryption or authentication. Traditional FTP does not inherently encrypt its control and data traffic, while HTTP is a general application-layer protocol rather than an SSH-based secure file-copy mechanism. Service provider administrators may use SCP when securely transferring files between routers, servers, and management systems. Therefore, SCP is correct.

Question 86

Which protocol provides a secure alternative to traditional FTP for transferring files?

1. TFTP
2. SCP
3. ARP
4. ICMP

Correct Answer: 2

Explanation

SCP provides secure file transfer using SSH and is therefore commonly used as a secure alternative to unencrypted file-transfer methods. It encrypts the connection and provides authentication through SSH mechanisms. TFTP is a lightweight file-transfer protocol but does not provide built-in security comparable to SSH-based methods. ARP is used for IPv4 address resolution, while ICMP supports network diagnostics and control messaging. In service provider environments, SCP can be useful when transferring configurations or software images securely. Therefore, SCP is the correct answer.

Question 87

Which protocol is designed to transfer files with minimal overhead but does not provide built-in authentication or encryption?

1. TFTP
2. SSH
3. IPsec
4. SCP

Correct Answer: 1

Explanation

Trivial File Transfer Protocol (TFTP) is a lightweight file-transfer protocol designed with minimal overhead. It commonly uses UDP and does not provide built-in authentication or encryption. TFTP can be useful in controlled environments for tasks such as transferring configuration files or boot images, but its lack of security features makes it unsuitable for many security-sensitive scenarios. SSH and SCP provide secure communication, while IPsec protects IP traffic through security mechanisms. Therefore, TFTP is the correct answer for a lightweight but unsecured file-transfer protocol.

Question 88

Which technology can provide network address translation for IPv4 traffic?

1. MPLS
2. NAT
3. BFD
4. LDP

Correct Answer: 2

Explanation

Network Address Translation (NAT) translates IP addresses between different addressing domains. A common use is translating private IPv4 addresses to a public IPv4 address for communication with external networks. NAT can conserve public IPv4 addresses and provide a degree of address-space separation. MPLS is a label-based forwarding technology, BFD provides rapid failure detection, and LDP distributes MPLS labels. NAT can be implemented in several forms, including static NAT, dynamic NAT, and Port Address Translation. Therefore, NAT is the correct answer.

Question 89

Which NAT method allows multiple private IPv4 hosts to share one public IPv4 address by using different transport-layer port numbers?

1. Static NAT
2. Dynamic NAT
3. PAT
4. Route Target

Correct Answer: 3

Explanation

Port Address Translation (PAT), also called NAT overload, allows multiple private IPv4 hosts to share a single public IPv4 address by differentiating sessions using transport-layer port numbers. When traffic leaves the private network, the NAT device records mappings between internal addresses and ports and the translated public address and ports. This allows many internal hosts to communicate using a limited number of public IPv4 addresses. Static NAT normally provides fixed one-to-one mappings, while dynamic NAT can allocate addresses from a pool. Therefore, PAT is correct.

Question 90

Which IPv4 address range is reserved for private addressing?

1. 8.8.8.0/24
2. 172.16.0.0/12
3. 1.1.1.0/24
4. 198.51.100.0/24

Correct Answer: 2

Explanation

The IPv4 range 172.16.0.0/12 is one of the RFC 1918 private address ranges. The three major private IPv4 ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Private addresses are not globally routable on the public Internet and are commonly used inside enterprise and service provider customer networks. The 8.8.8.0/24 range is associated with publicly reachable Google DNS addresses, while 1.1.1.0/24 is associated with Cloudflare’s public services. Therefore, 172.16.0.0/12 is correct.

Question 91

Which IPv6 address type is designed for communication with the nearest member of a group according to routing metrics?

1. Multicast
2. Anycast
3. Broadcast
4. Unicast only

Correct Answer: 2

Explanation

An IPv6 anycast address is assigned to multiple interfaces, and packets sent to that address are delivered to the topologically nearest interface according to the routing system. Anycast is useful for distributed services where multiple instances can provide the same service. IPv6 does not use broadcast in the same way IPv4 does; multicast is used for many one-to-many communication functions. Unicast identifies a single interface or destination from the perspective of routing. Therefore, anycast is the correct address type for reaching the nearest member of a group.

Question 92

Which IPv6 mechanism replaces traditional IPv4 broadcast for many discovery functions?

1. Multicast
2. NAT
3. ARP
4. GRE

Correct Answer: 1

Explanation

IPv6 uses multicast for many functions that traditionally relied on IPv4 broadcast. IPv6 Neighbor Discovery Protocol, for example, uses ICMPv6 multicast messages to discover neighbors and routers. IPv6 does not use broadcast addresses in the same manner as IPv4. ARP is also not used by IPv6; Neighbor Discovery replaces ARP functionality. NAT is an address-translation technology, while GRE is a tunneling protocol. Therefore, multicast is the correct mechanism for many IPv6 discovery operations.

Question 93

Which protocol is used by IPv6 Neighbor Discovery to discover neighboring devices and routers?

1. ICMPv4
2. ICMPv6
3. FTP
4. LDP

Correct Answer: 2

Explanation

IPv6 Neighbor Discovery Protocol uses ICMPv6 messages to perform functions such as router discovery, neighbor discovery, address resolution, and duplicate address detection. Important message types include Router Solicitation, Router Advertisement, Neighbor Solicitation, and Neighbor Advertisement. This functionality replaces several mechanisms traditionally provided by IPv4 ARP and router discovery processes. FTP is a file-transfer protocol, LDP distributes MPLS labels, and ICMPv4 is associated with IPv4. Therefore, ICMPv6 is the correct protocol for IPv6 Neighbor Discovery.

Question 94

Which IPv6 address prefix identifies link-local addresses?

1. FE80::/10
2. FC00::/7
3. 2000::/3
4. FF00::/8

Correct Answer: 1

Explanation

IPv6 link-local addresses use the FE80::/10 prefix. These addresses are automatically available on IPv6-enabled interfaces and are intended for communication on the local link. They are not routed between different IPv6 links. The FC00::/7 range is associated with unique local addresses, 2000::/3 contains global unicast addresses, and FF00::/8 identifies multicast addresses. Link-local addresses are especially important for IPv6 neighbor discovery and routing protocol operations. Therefore, FE80::/10 is the correct prefix.

Question 95

Which IPv6 address type is commonly used for private internal addressing?

1. Global unicast
2. Unique local
3. Multicast
4. Link-local only

Correct Answer: 2

Explanation

Unique Local Addresses (ULAs) are IPv6 addresses intended for local or private use within organizations and networks. They are defined within the FC00::/7 range, with commonly used ULA space coming from the FD00::/8 portion. ULAs are not intended to be globally routed across the public Internet. Global unicast addresses are globally routable, multicast addresses identify groups of interfaces, and link-local addresses operate only on the local link. Therefore, unique local addressing is the appropriate IPv6 equivalent for private internal addressing.

Question 96

Which technology can provide redundancy by allowing multiple routers to share a virtual gateway address?

1. HSRP
2. LDP
3. BGP
4. NTP

Correct Answer: 1

Explanation

Hot Standby Router Protocol (HSRP) provides first-hop gateway redundancy by allowing multiple routers to participate in a virtual router group. Hosts can use a virtual IP address as their default gateway, while one router actively forwards traffic and another can take over if the active router fails. This improves gateway availability without requiring hosts to change their configured default gateway. LDP is used for MPLS label distribution, BGP exchanges routing information, and NTP synchronizes clocks. Therefore, HSRP is the correct technology for this type of gateway redundancy.

Question 97

Which protocol is commonly used to provide gateway redundancy with an open standard rather than a Cisco-proprietary protocol?

1. HSRP
2. VRRP
3. LDP
4. RSVP

Correct Answer: 2

Explanation

Virtual Router Redundancy Protocol (VRRP) is an open-standard first-hop redundancy protocol. It allows multiple routers to participate in a virtual router group and share a virtual IP address. One router performs the active forwarding role while another can assume that role if the active router fails. HSRP also provides first-hop redundancy but is historically associated with Cisco implementations. LDP and RSVP are MPLS-related protocols. Therefore, VRRP is the correct answer when an open-standard gateway redundancy protocol is required.

Question 98

Which technology allows two or more physical links to operate as a single logical bundle?

1. LACP
2. BFD
3. LDP
4. NTP

Correct Answer: 1

Explanation

Link Aggregation Control Protocol (LACP) is used to dynamically negotiate and maintain link aggregation between compatible devices. Multiple physical Ethernet links can be combined into a logical port-channel, increasing available bandwidth and providing redundancy. If one physical member fails, traffic can continue through the remaining active members, subject to the configuration and capacity. BFD is used for failure detection, LDP distributes MPLS labels, and NTP provides time synchronization. Therefore, LACP is the correct protocol for dynamically managing a link aggregation group.

Question 99

Which protocol is commonly used to detect and prevent Layer 2 switching loops?

1. BGP
2. STP
3. LDP
4. RSVP

Correct Answer: 2

Explanation

Spanning Tree Protocol (STP) prevents Layer 2 switching loops by logically blocking redundant paths while maintaining them as potential backup paths. Without loop prevention, redundant Ethernet connections could cause broadcast storms, duplicate frames, and MAC-table instability. STP builds a loop-free logical topology and can reconverge when topology changes occur. BGP is a Layer 3 routing protocol, LDP distributes MPLS labels, and RSVP can support signaling and traffic engineering. Therefore, STP is the correct technology for preventing Layer 2 switching loops.

Question 100

Which service provider technology is designed to transport Layer 2 frames across an MPLS network using a pseudowire?

1. L2TP
2. VPWS
3. NTP
4. BFD

Correct Answer: 2

Explanation

Virtual Private Wire Service (VPWS) provides point-to-point Layer 2 VPN connectivity across a service provider network. It can use a pseudowire to emulate a direct Layer 2 connection between customer endpoints across an MPLS infrastructure. Customer Ethernet frames are transported through the provider network while the underlying provider topology remains hidden from the customer. VPWS is therefore useful when customers require transparent point-to-point Layer 2 connectivity. NTP provides time synchronization, BFD provides failure detection, and L2TP has different tunneling applications. Therefore, VPWS is the correct answer.