Tüm alıştırma soruları

1987 soru

Tüm türler1,987 Çoktan seçmeli1,020 Çoklu seçim452 Sayısal18 Eşleştirme229 Sıralama203 Boşluk doldurma22 Kısa cevap43

A network engineer is configuring first-hop redundancy on router R1's GigabitEthernet0/1 interface, which has been assigned the physical IPv4 address $192.168.20.1/24$ . The engineer initially attempts to configure HSRP Group 20 using the command `standby 20 ip 192.168.20.1`, but then evaluates migrating the design to VRRPv2 using the command `vrrp 20 ip 192.168.20.1`. Assuming default protocol parameters are used, which operational distinction correctly describes how HSRP and VRRP handle this configuration attempt and default preemption behavior?

HSRP rejects configuring the virtual IP address to match a physical interface IP address, whereas VRRP permits it, automatically assigning a priority of 255 to the IP address owner with mandatory preemption enabled.

HSRP accepts assigning the physical interface IP address as the virtual IP address but disables preemption by default, whereas VRRP rejects any virtual IP configuration that matches an existing physical interface IP.

Both protocols permit assigning the physical interface IP address as the virtual IP address, but HSRP enables preemption by default while VRRP disables preemption by default.

VRRP rejects using the physical interface IP address because VRRP master election requires an unassigned host address, whereas HSRP requires the virtual IP to match the active router's physical interface IP address.

Cevabı ve açıklamayı göster

Cevap: HSRP rejects configuring the virtual IP address to match a physical interface IP address, whereas VRRP permits it, automatically assigning a priority of 255 to the IP address owner with mandatory preemption enabled.

Cevap

The correct answer accurately contrasts the Virtual IP assignment constraints and preemption defaults between Cisco HSRP and standard VRRP. HSRP mandates that the virtual IP address must be an unassigned, unique IP within the local subnet and will throw a configuration error if matched to a physical interface address. Furthermore, HSRP preemption is disabled by default. In contrast, VRRP allows the virtual IP address to be identical to a physical interface IP address on the router (making it the IP address owner with priority 255), and VRRP preemption is enabled by default.

Adım Adım Çözüm

Evaluate HSRP Virtual IP assignment rules

HSRP requires the Virtual IP address to be a unique IP address within the subnet that is NOT assigned to any physical interface on participating routers.

Cisco IOS HSRP prevents IP address duplication on physical interfaces to prevent ARP and routing loop anomalies.

Evaluate VRRP Virtual IP assignment rules (IP Address Owner)

VRRP permits the virtual IP address to match the primary physical IPv4 address of an interface.

When a router's interface physical IP matches the VRRP virtual IP, that router acts as the VRRP IP Address Owner and is automatically assigned the maximum priority of 255.

Analyze default preemption behavior in HSRP versus VRRP

HSRP preemption is disabled by default, whereas VRRP preemption is enabled by default.

VRRP RFC standards mandate that preemption is enabled out-of-the-box, ensuring a higher priority router always assumes the Master role, especially when priority is 255.

Anahtar Kavram

First Hop Redundancy Protocol (FHRP) Virtual IP Assignment and Preemption Defaults

Tahmini Süre:2m 0s

Soru 1642Soru →

A network technician needs to configure a Cisco router to operate as an Network Time Protocol (NTP) client and synchronize its internal system clock with a central time server located at IP address 172.16.10.100. Which global configuration command must be executed on the router to accomplish this task?

ntp server 172.16.10.100

ntp peer 172.16.10.100

ntp master 172.16.10.100

clock set 172.16.10.100

Cevabı ve açıklamayı göster

Cevap: ntp server 172.16.10.100

Cevap

The command 'ntp server 172.16.10.100' in global configuration mode configures the local Cisco device as an NTP client that synchronizes its system time from the specified IP address.

The command 'ntp server 172.16.10.100' instructs the Cisco IOS router to operate as an NTP client in client-server mode, sending unicast NTP requests to the specified IP address to synchronize its clock.

Adım Adım Çözüm

Identify the role required for the router.

The router must act as an NTP client receiving time from an external server.

The requirement states that the router needs to synchronize its clock to an existing centralized server at IP address 172.16.10.100.

Evaluate Cisco IOS NTP configuration commands.

The command 'ntp server <ip-address>' establishes client-server NTP association.

Global configuration command 'ntp server 172.16.10.100' configures the router to query the NTP daemon at 172.16.10.100 for time updates.

Anahtar Kavram

NTP Client Configuration

Soru 1643Soru →

An enterprise client host without a cached DNS entry needs to connect to an external server using its domain name. Place the steps of the full name resolution flow in the correct chronological order, starting from the client's initial lookup request to the final response delivery.

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Cevap

The correct chronological sequence begins with the client host issuing a recursive query to the internal DNS server after checking its local cache. Next, the internal DNS server executes iterative lookups starting at a root DNS server, followed by the TLD DNS server, and finally the domain's authoritative DNS server. Upon receiving the A/AAAA record from the authoritative server, the internal DNS server caches the result and delivers the IP address to the requesting client.

The correct order follows the standard hierarchy of enterprise DNS name resolution. First, the client checks its local cache and queries its local DNS server recursively. Second, if un-cached, the internal recursive DNS server initiates iterative lookups starting at the root servers. Third, the root server redirects the query to the TLD server. Fourth, the TLD server refers the query to the authoritative name server. Fifth, the authoritative name server provides the IP mapping, which the internal server caches before replying to the client host.

Adım Adım Çözüm

Evaluate host-level resolution steps

Client host checks local cache/hosts file, then sends a recursive lookup request to the configured internal DNS server.

Hosts must exhaust local name resolution mechanisms before querying network resolvers over port 53.

Trace top-of-hierarchy DNS server lookup

Internal recursive server queries a Root name server and receives a referral to the TLD name servers.

Iterative resolution moves top-down through the domain namespace starting at the root (".").

Trace mid-hierarchy DNS server lookup

Internal recursive server queries the TLD server (such as .com) and receives a referral to the authoritative name server.

TLD servers delegate authority for specific subdomains to organizational name servers.

Trace authoritative response acquisition

Internal recursive server queries the domain's authoritative name server and receives the final mapping.

Only the authoritative DNS server for a domain holds the definitive zone file records.

Complete recursive loop to client

Internal recursive server caches the mapping according to TTL and returns the resolved address to the client.

The client receives a single final response to satisfy its initial recursive query.

Anahtar Kavram

DNS Resolution Hierarchy and Iterative vs Recursive Query Roles

Soru 1644Soru →

A network administrator is configuring a backup floating static route on router R1 to reach the internal subnet $10.20.0.0/16$ . The primary path to this destination is currently learned dynamically via OSPF, which has a default Administrative Distance of $110$ . The backup route should traverse next-hop IPv4 address $192.168.12.2$ and must enter the routing table only when the primary OSPF path becomes unavailable. Which Cisco IOS command correctly achieves this objective?

ip route 10.20.0.0 255.255.0.0 192.168.12.2 120

ip route 10.20.0.0 255.255.0.0 192.168.12.2 90

ip route 10.20.0.0 255.255.0.0 192.168.12.2 110

ip route 10.20.0.0 0.0.255.255 192.168.12.2 120

Cevabı ve açıklamayı göster

Cevap: ip route 10.20.0.0 255.255.0.0 192.168.12.2 120

Cevap

The correct command is 'ip route 10.20.0.0 255.255.0.0 192.168.12.2 120'.

A floating static route is configured by specifying an administrative distance higher than that of the primary routing protocol. Since OSPF has an Administrative Distance of 110, setting an AD of 120 ensures the static route remains untracked in the routing table during normal operation and only activates if the primary OSPF route drops out.

Adım Adım Çözüm

Determine the destination prefix and subnet mask for 10.20.0.0/16.

Destination prefix is 10.20.0.0 and the 16-bit subnet mask in dotted-decimal format is 255.255.0.0.

Cisco IOS static route syntax uses subnet masks rather than wildcard masks.

Identify the next-hop IP address.

Next-hop IP address is 192.168.12.2.

The scenario explicitly designates 192.168.12.2 as the exit path for backup traffic.

Select an Administrative Distance (AD) greater than the primary route's AD.

OSPF default AD is 110; therefore, the floating static route requires an AD greater than 110 (such as 120).

Routers prefer lower Administrative Distance values. Assigning a value higher than 110 ensures the static route remains inactive in the routing table until OSPF fails.

Anahtar Kavram

Floating Static Routes and Administrative Distance

Soru 1645Soru →

Four Cisco routers (R1, R2, R3, and R4) are connected to a shared Ethernet broadcast segment (10.1.1.0/24). OSPFv2 process 1 is enabled simultaneously on all router interfaces attached to this segment. The relevant interface and router parameters are configured as follows:

- R1: Interface OSPF Priority = 100, Router ID = 192.168.1.1
- R2: Interface OSPF Priority = 200, Router ID = 10.2.2.2
- R3: Interface OSPF Priority = 200, Router ID = 10.3.3.3
- R4: Interface OSPF Priority = 0, Router ID = 10.254.254.254

Assuming all routers initialize at the same moment without any existing DR or BDR active on the link, which router will be elected as the Backup Designated Router (BDR)?

Cevabı ve açıklamayı göster

Cevap: R2

Cevap

R2 will be elected as the Backup Designated Router (BDR).

In OSPF multiaccess networks, DR and BDR elections evaluate interface priority first. Routers with priority 0 (R4) are excluded. Between R2 and R3 (both priority 200), R3 wins the DR role due to its higher Router ID (10.3.3.3 > 10.2.2.2). R2 has the highest remaining priority among eligible non-DR routers, making it the BDR.

Adım Adım Çözüm

Filter out ineligible routers based on OSPF interface priority.

R4 has an interface priority of 0 and is excluded from both DR and BDR elections.

A priority value of 0 explicitly prevents a router from becoming a DR or BDR.

Compare the interface priority values of the remaining eligible routers (R1, R2, R3).

R2 and R3 tie for the highest priority (200), while R1 has a lower priority (100).

OSPF elects DR and BDR based primarily on the highest interface priority.

Break the tie between R2 and R3 to elect the Designated Router (DR).

R3's Router ID (10.3.3.3) is higher than R2's Router ID (10.2.2.2), so R3 becomes DR.

When priority values are identical, the router with the highest Router ID wins the election.

Select the Backup Designated Router (BDR) from the remaining eligible routers.

R2 becomes the BDR because it has the highest remaining priority (200).

After DR selection, the router with the highest remaining priority (or highest Router ID in case of another tie) is selected as BDR.

Anahtar Kavram

OSPFv2 DR/BDR Election Rules and Priority 0 Ineligibility

Soru 1646Soru →

A Cisco router initializes an OSPFv2 routing process without an explicitly configured OSPF router-id. The interface configuration and operational states are as follows:

• Loopback0: 172.16.1.10/24 (up/up)
• Loopback1: 172.16.2.5/24 (up/up)
• GigabitEthernet0/0: 10.1.1.1/24 (up/up)
• GigabitEthernet0/1: 192.168.100.1/24 (up/up)

What IP address will be selected as the OSPFv2 router ID?

Cevabı ve açıklamayı göster

Cevap: 172.16.2.5

Cevap

172.16.2.5

OSPFv2 determines the router ID using a strict three-tier priority order: 1) Explicitly configured router-id command under the OSPF process, 2) Highest IPv4 address among operational (up/up) loopback interfaces, 3) Highest IPv4 address among operational physical (non-loopback) interfaces. Because no manual router ID is specified, OSPF evaluates the loopback interfaces. Between Loopback0 (172.16.1.10) and Loopback1 (172.16.2.5), 172.16.2.5 is numerically higher and is selected as the router ID, overriding the physical interface address 192.168.100.1.

Adım Adım Çözüm

Check for a manually configured OSPF router ID under the OSPF process configuration.

No manual router ID is configured.

Explicit configuration always takes top priority in OSPF router ID selection.

Evaluate operational (up/up) loopback interfaces for the highest IPv4 address.

Loopback0 (172.16.1.10) and Loopback1 (172.16.2.5) are active. 172.16.2.5 is numerically greater than 172.16.1.10.

If no manual router ID exists, OSPF selects the highest IPv4 address among active loopback interfaces.

Determine the final OSPFv2 router ID without considering physical interfaces.

172.16.2.5 is chosen as the router ID.

Active physical interface IP addresses (such as 192.168.100.1) are only evaluated if zero active loopback interfaces exist.

Anahtar Kavram

OSPFv2 Router ID Election Precedence

Tahmini Süre:1m 0s

Soru 1647Soru →

A network administrator is connecting a Cisco Catalyst 9800 Series Wireless LAN Controller to an upstream Cisco Catalyst switch using link aggregation (LAG) with LACP. In what logical order should the administrator execute the steps on the Catalyst switch to provision the EtherChannel interface and physical member ports?

Öğeleri doğru sıraya koymak için sürükleyin

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Cevap

The correct sequence begins with creating the logical port-channel interface on the switch, applying trunking and VLAN parameters to that logical interface, selecting the physical member interfaces, adding the physical interfaces to the EtherChannel using active LACP mode, and finally verifying bundle operation with the 'show etherchannel summary' command.

To establish link aggregation between a Cisco Catalyst switch and a Cisco Wireless LAN Controller using LACP, standard configuration methodology requires initializing the logical port-channel interface first. Trunking settings (such as switchport mode trunk and VLAN assignments) are defined on the logical port-channel. Next, the target physical member interfaces are selected and bound to the channel group using active LACP mode. Finally, running operational verification commands confirms proper link aggregation state.

Adım Adım Çözüm

Create the virtual port-channel interface

The logical interface Port-channel 1 is initialized.

Creating the logical interface first provides the administrative entity where trunking parameters will be defined.

Configure trunking properties on the port-channel

The port-channel interface is set to switchport mode trunk with explicit native and allowed VLAN parameters.

Defining trunk settings directly on the port-channel interface guarantees uniform configuration for all associated physical ports.

Select physical switch interfaces

The physical ports connected to the wireless controller are selected via interface range configuration mode.

Grouping physical interfaces prepares them for enrollment into the EtherChannel bundle.

Bind physical ports to the channel group using LACP

The command 'channel-group 1 mode active' enables dynamic LACP negotiation on the physical ports.

LACP active mode allows the switch to initiate negotiation with the Wireless LAN Controller.

Verify EtherChannel operation

Output displays flag 'SU' for the port-channel and flag 'P' for each active member port.

Verifying status confirms that LACP negotiation succeeded and traffic can be forwarded across the aggregated links.

Anahtar Kavram

Cisco switch EtherChannel and LACP configuration for WLC trunking

Soru 1648Soru →

A network administrator configures a core switch interface with the IPv4 address $10.50.180.75/21$ . What is the broadcast address for the subnetwork to which this interface belongs?

10.50.183.255

10.50.180.255

10.50.183.254

10.50.191.255

Cevabı ve açıklamayı göster

Cevap: $10.50.183.255$

Cevap

The broadcast address for the subnetwork is

10.50.183.255

The prefix /21 designates 21 subnet bits, yielding a subnet mask of

255.255.248.0

. In the third octet, subnets increment in steps of 8. For the IP address

10.50.180.75

, the containing subnet boundary starts at

10.50.176.0

and spans up to

10.50.183.255

. Since the broadcast address requires all host bits set to 1,

10.50.183.255

is the correct subnet broadcast address.

Adım Adım Çözüm

Determine the subnet mask and block size from the CIDR prefix.

A /21 prefix provides 21 network bits and 11 host bits. In dotted-decimal form, this is

255.255.248.0

. The host portion spans into the third octet. The block size in the third octet is

256 - 248 = 8

Prefix length identifies where the network portion ends and the host portion begins.

Calculate the network address for the given IP address

10.50.180.75

Dividing the third octet value (180) by the block size (8) gives

180 / 8 = 22.5

. Multiplying

22 \times 8 = 176

. Thus, the network address is

10.50.176.0/21

The network address is the lowest boundary of the subnet block.

Calculate the broadcast address.

Adding the block size minus 1 (

8 - 1 = 7

) to the third octet network boundary gives

176 + 7 = 183

. Setting all host bits in the fourth octet to binary 1s gives 255. The broadcast address is

10.50.183.255

The broadcast address is the highest possible IP address within the subnet range.

Anahtar Kavram

IPv4 Subnet Boundary and Broadcast Address Derivation

Tahmini Süre:1m 30s

Soru 1649Soru →

An enterprise network engineer configures an internal host to resolve domain names via a local Active Directory DNS server, which is configured to forward external queries to a public DNS resolver. During a packet capture analysis on the firewall boundary, the engineer observes that a specific DNS query originating from the internal AD DNS server towards an external authoritative DNS server for a large DNSSEC-signed domain initially uses UDP destination port 53, receives a response with the TrunCation (TC) bit set to 1, and immediately follows up with a new request to the same target server using TCP destination port 53. Which statement accurately explains the fundamental reason for this protocol switch during the name resolution process?

The DNS server switches to TCP because the response payload exceeds the negotiated maximum transmission unit (or 512-byte traditional UDP DNS limit), requiring TCP stream reliability to reassemble and guarantee delivery of large resource record sets.

The DNS server switches to TCP because UDP lacks native sequencing mechanisms, causing the firewall to dynamically force TCP fallback for all recursive domain lookups that require multi-packet reassembly.

The DNS server switches to TCP because authoritative DNS servers only listen on TCP port 53 for recursive lookup requests, while UDP port 53 is strictly reserved for iterative client-to-resolver queries.

The DNS server switches to TCP because DNSSEC security validation requires an initial UDP handshake to authenticate the root hints before opening a persistent TCP control session for payload encryption.

Cevabı ve açıklamayı göster

Cevap: The DNS server switches to TCP because the response payload exceeds the negotiated maximum transmission unit (or 512-byte traditional UDP DNS limit), requiring TCP stream reliability to reassemble and guarantee delivery of large resource record sets.

Cevap

The DNS server switches to TCP port 53 because the DNS response payload exceeds the maximum supported UDP DNS buffer size, causing the responder to set the TrunCation (TC) bit and prompting the requester to re-query over TCP.

Standard DNS operations use UDP port 53 for fast, lightweight name resolution. However, when a DNS answer payload (such as large DNSSEC resource record sets) exceeds the supported UDP datagram size limit, the responding server truncates the response and sets the TrunCation (TC) flag bit in the DNS header. When the querying DNS entity detects TC=1, standard DNS behavior dictates establishing a TCP connection to port 53 and re-transmitting the query to receive the full, untruncated answer payload.

Adım Adım Çözüm

Analyze the DNS packet capture details

Identified that the initial UDP query returned a DNS response with the TC (TrunCation) bit set to 1.

The TC bit indicates that the responding server truncated the answer because the payload exceeded the maximum allowable DNS UDP message size.

Evaluate transport layer behavior for DNS

DNS operates primarily over UDP port 53 for speed, but falls back to TCP port 53 when responses are truncated.

TCP provides stream-based transmission capable of handling payload sizes larger than the single-datagram UDP limit without losing data integrity.

Select the option that correctly describes TC bit functionality and TCP fallback

Confirmed that payload overflow leading to TC=1 triggers an immediate retry over TCP port 53.

This is a core DNS specification behavior defined in RFC 1035 and enhanced by EDNS0.

Anahtar Kavram

DNS Transport Layer Mechanics and TC Bit Truncation Fallback

Tahmini Süre:2m 0s

Soru 1650Soru →

A network engineer is configuring a backup static route on a Cisco router for the destination network $10.100.4.0/24$ . The primary path to this network is currently learned dynamically via internal EIGRP, which uses a default Administrative Distance of $90$ . The engineer needs the static route to remain inactive in the routing table unless the EIGRP path fails. Which command correctly configures this floating static route?

ip route 10.100.4.0 255.255.255.0 192.168.12.2 130

ip route 10.100.4.0 255.255.255.0 192.168.12.2 80

ip route 10.100.4.0 255.255.255.0 192.168.12.2

ip route 10.100.4.0 255.255.255.0 192.168.12.2 90

Cevabı ve açıklamayı göster

Cevap: ip route 10.100.4.0 255.255.255.0 192.168.12.2 130

Cevap

The command specifying an administrative distance of 130 correctly configures the floating static route.

A floating static route requires an Administrative Distance (AD) value higher than that of the primary route protocol. Because internal EIGRP uses a default AD of 90, specifying an AD of 130 ensures the static route remains out of the IP routing table until the primary EIGRP route fails.

Adım Adım Çözüm

Identify the Administrative Distance (AD) of the primary routing protocol.

Internal EIGRP has a default AD of 90.

Floating static routes rely on AD precedence to remain dormant while the primary path is operational.

Determine the required Administrative Distance for the floating static route.

The static route must be assigned an AD value strictly greater than 90 (e.g., 130).

Cisco IOS prefers routes with lower AD values. Assigning an AD higher than 90 ensures the static route is installed into the routing table only if the EIGRP route is withdrawn.

Evaluate the syntax options for the correct trailing AD value.

The command 'ip route 10.100.4.0 255.255.255.0 192.168.12.2 130' correctly appends the custom AD 130.

It successfully creates a floating static backup route.

Anahtar Kavram

Floating Static Routes and Administrative Distance

Soru 1651Soru →

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router to allow internal hosts in the $172.16.50.0/24$ subnet to access the Internet using the public IP address on interface GigabitEthernet0/0/0. Internal users report that they cannot establish any outbound internet connections. The running configuration reveals the following details:

interface GigabitEthernet0/0/0
ip address 203.0.113.1 255.255.255.248
ip nat outside
!
interface GigabitEthernet0/0/1
ip address 172.16.50.1 255.255.255.0
!
ip access-list standard NAT_ACL
permit 172.16.50.0 0.0.0.255
!
ip nat inside source list NAT_ACL interface GigabitEthernet0/0/0 overload

Which configuration change must be made on the router to resolve this issue?

Configure the ip nat inside command under interface GigabitEthernet0/0/1.

Remove the overload keyword from the ip nat inside source command.

Change the ACL source network to 172.32.50.0 0.0.0.255 because 172.16.50.0 is not a valid private IP range.

Append an explicit permit any statement to the end of access-list NAT_ACL.

Cevabı ve açıklamayı göster

Cevap: Configure the ip nat inside command under interface GigabitEthernet0/0/1.

Cevap

Configure the ip nat inside command under interface GigabitEthernet0/0/1.

For Cisco IOS NAT to operate, at least one interface must be designated as 'ip nat inside' and at least one interface as 'ip nat outside'. In the provided configuration, interface GigabitEthernet0/0/1 lacks the 'ip nat inside' command, so packets arriving from internal hosts are not identified for translation.

Adım Adım Çözüm

Analyze the existing router configuration for NAT/PAT components.

Interface GigabitEthernet0/0/0 is properly marked with 'ip nat outside', NAT_ACL permits

172.16.50.0/24

, and the global translation statement maps NAT_ACL to GigabitEthernet0/0/0 with 'overload'.

For Cisco IOS NAT/PAT to process packets, interfaces must be designated as inside or outside, and traffic must cross between them.

Inspect the internal interface configuration.

Interface GigabitEthernet0/0/1 is missing the 'ip nat inside' command.

Without 'ip nat inside' on the internal gateway interface, incoming packets from

172.16.50.0/24

are routed normally without undergoing Network Address Translation.

Identify the required fix.

Add 'ip nat inside' under interface GigabitEthernet0/0/1 configuration.

This establishes the boundary between internal private addresses and the external public interface, enabling PAT processing.

Anahtar Kavram

Inside and Outside NAT Interface Designation

Tahmini Süre:1m 30s

Soru 1652Soru →

An network engineer is configuring HSRP group 15 on a Cisco router interface that has been assigned the primary IPv4 address $172.16.20.2/24$ . Which requirement must be met when defining the HSRP virtual IPv4 address for this interface?

The virtual IPv4 address must belong to the

172.16.20.0/24

subnet and cannot match the physical IPv4 address of any router in the group.

The virtual IPv4 address must match the physical IPv4 address assigned to the active router interface.

The virtual IPv4 address must be assigned from a distinct IPv4 subnet that is separate from the physical subnet of the interface.

The virtual IPv4 address can be set to any valid host IPv4 address because HSRP relies exclusively on MAC address translation.

Cevabı ve açıklamayı göster

Cevap: The virtual IPv4 address must belong to the $172.16.20.0/24$ subnet and cannot match the physical IPv4 address of any router in the group.

Cevap

The HSRP virtual IPv4 address must be in the same IPv4 subnet as the interface's physical IP address (

172.16.20.0/24

), but it cannot be identical to the physical IPv4 address configured on any router participating in the HSRP group.

In HSRP (v1 and v2), the virtual IP address configured via the command `standby <group> ip <ip-address>` must reside within the same IP subnet as the router interface's physical IP address so local LAN clients can reach it as their default gateway. However, Cisco IOS explicitly blocks assigning a virtual IP address that matches any physical IP assigned to a router interface in the group.

Adım Adım Çözüm

Identify the physical IP subnet of the interface.

The interface has IP address

172.16.20.2/24

, placing it in the

172.16.20.0/24

subnet.

Default gateway traffic from LAN clients must be reachable within their local IP broadcast domain.

Apply the HSRP virtual IP assignment rule.

Select an unassigned IP address within

172.16.20.0/24

(e.g.,

172.16.20.1

Cisco HSRP requires virtual IP addresses to belong to the local subnet and strictly forbids reusing any physical interface IP address of HSRP routers.

Anahtar Kavram

HSRP Virtual IP Address Assignment Requirements

Soru 1653Soru →

An enterprise host needs to resolve the IP address of an internal web application server (app.corp.local) after the local cache has expired. Place the steps of the name resolution process in the correct chronological order from first to last.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence of DNS name resolution steps is: 1) The host checks its local OS DNS client resolver cache and local hosts file. 2) The host encapsulates a recursive DNS query in a UDP datagram with destination port 53 and sends it to its primary configured DNS server. 3) The enterprise DNS server receives the query and checks its authoritative DNS zones. 4) The DNS server formulates an authoritative response packet containing the requested A record. 5) The host receives the DNS response packet and stores the IP address mapping in its local DNS resolver cache.

The correct order follows the standard host-to-server DNS name resolution flow: first, local host resources (cache and hosts file) are inspected. If unresolved, the client sends a recursive UDP query (destination port 53) to its configured local DNS server. The DNS server processes the query against its zone database, generates an authoritative response containing the A record, and returns it to the host. Finally, the host receives the response and caches the IP address locally.

Adım Adım Çözüm

Evaluate local host resolution mechanisms.

Local resolver cache and hosts file are queried first prior to generating outbound network requests.

Checking local host memory avoids unnecessary network traffic and reduces latency.

Transmit DNS request over the local network connection.

A UDP datagram targeted to destination port 53 is forwarded to the designated local DNS server.

Standard DNS queries use UDP port 53 for low-overhead client-to-server communications.

Process query at the targeted enterprise DNS server.

The server checks its local authoritative zone files for matching domain records.

Because the domain is internal (corp.local), the internal DNS server acts as the authoritative source.

Build DNS server response payload.

An authoritative DNS answer payload containing the IPv4 (A) record is created.

The server must supply the mapped IP address back to the requesting client.

Process response on the requesting client host.

The client receives the response and caches the entry according to the record's Time-to-Live (TTL).

Caching allows subsequent applications on the host to reuse the resolved IP address without repeating the DNS lookup.

Anahtar Kavram

Client DNS resolution sequence and DNS server roles

Soru 1654Soru →

A network administrator needs to assign interface GigabitEthernet1/0/8 on a Cisco Catalyst switch to VLAN 70 (named RESEARCH) as a static access port. The configuration must force the interface into access mode and statically assign it to VLAN 70. Which TWO commands must be entered in interface configuration mode to complete this setup?

Geçerli olan tümünü seçin

switchport mode access

switchport trunk native vlan 70

switchport access vlan 70

vlan 70

Cevabı ve açıklamayı göster

Cevap: switchport mode access; switchport access vlan 70

Cevap

The correct commands to execute in interface configuration mode are 'switchport mode access' and 'switchport access vlan 70'.

Configuring an access port on a Cisco switch requires defining the port behavior as access mode ('switchport mode access') and specifying the target VLAN assignment ('switchport access vlan 70'). Together, these commands ensure untagged traffic on the port belongs exclusively to VLAN 70.

Adım Adım Çözüm

Set the interface mode to access

Interface is explicitly designated as an access port using 'switchport mode access'.

Ensures the port operates exclusively as an access interface and disables DTP negotiation into trunking mode.

Assign the specific access VLAN membership

Interface is associated with VLAN 70 using 'switchport access vlan 70'.

Directs untagged traffic entering or leaving GigabitEthernet1/0/8 into broadcast domain VLAN 70.

Anahtar Kavram

Configuring static access ports in Cisco IOS requires enforcing access mode and setting the access VLAN membership at the interface configuration prompt.

Soru 1655Soru →

A network administrator needs to configure SNMPv3 on a Cisco IOS router to support both message integrity verification using SHA and payload encryption using AES. Which SNMPv3 security level must be configured to meet these security requirements?

authPriv

authNoPriv

noAuthNoPriv

privNoAuth

Cevabı ve açıklamayı göster

Cevap: authPriv

Cevap

The authPriv security level must be configured because it provides both authentication and privacy (encryption).

The authPriv security level is the highest security mode available in SNMPv3. It combines authentication algorithms (such as HMAC-SHA or HMAC-MD5) to ensure packet integrity and sender authentication with encryption algorithms (such as AES or DES) to provide privacy for management traffic.

Adım Adım Çözüm

Identify the required security parameters from the scenario.

The requirements are SHA authentication and AES payload encryption.

The administrator explicitly specifies message integrity verification and data confidentiality.

Map the requirements to the standard SNMPv3 security models.

The authPriv security level meets both requirements.

SNMPv3 defines three security levels: noAuthNoPriv (no authentication, no encryption), authNoPriv (authentication without encryption), and authPriv (authentication with encryption).

Anahtar Kavram

SNMPv3 Security Levels (noAuthNoPriv, authNoPriv, authPriv)

Soru 1656Soru →

A network administrator is analyzing the operational characteristics of a Cisco Catalyst switch block running Rapid PVST+. Which two statements accurately describe Rapid PVST+ port roles and bridge priority structures?

Geçerli olan tümünü seçin

An Alternate port remains in the Discarding state while receiving BPDUs from neighboring switches to provide an alternate path to the Root Bridge.

A Backup port receives BPDUs from the same switch on a shared medium segment to offer redundant connectivity for the designated segment.

Configuring bridge priorities for VLANs in Rapid PVST+ must be specified in increments of 2048 to allow space for the 12-bit System ID Extension.

Enabling PortFast on switch-to-switch trunk ports causes the interface to transition immediately into the Learning state to accelerate STP convergence.

Cevabı ve açıklamayı göster

Cevap: An Alternate port remains in the Discarding state while receiving BPDUs from neighboring switches to provide an alternate path to the Root Bridge.; A Backup port receives BPDUs from the same switch on a shared medium segment to offer redundant connectivity for the designated segment.

Cevap

The correct statements are that an Alternate port remains in the Discarding state while receiving BPDUs to provide an alternate root path, and a Backup port receives BPDUs from its own switch on a shared segment to provide redundant segment access.

In Rapid PVST+, an Alternate port receives BPDUs from neighboring switches to serve as an instant backup to the Root Port while maintaining a Discarding state. A Backup port receives BPDUs from its own switch across a shared collision domain (such as a hub) to serve as a backup to a Designated port.

Adım Adım Çözüm

Evaluate the operational characteristics of Rapid PVST+ Alternate and Backup port roles.

Alternate ports receive BPDUs from other switches to back up the Root Port (in Discarding state). Backup ports receive BPDUs from the local switch on shared media to back up a Designated port.

RSTP (802.1w) defines distinct roles for discarded links based on whether the incoming BPDUs originate from an external switch (Alternate) or the local switch itself (Backup).

Evaluate the calculation rules for System ID Extension and Bridge Priority in Cisco switches.

Bridge priority uses the 4 most significant bits of the 16-bit priority field, requiring configured values to be multiples of 4096 (

2^{12}

Values like 2048 are invalid because the lower 12 bits are strictly reserved for carrying the VLAN ID.

Analyze PortFast state transitions and placement rules.

PortFast transitions ports directly to Forwarding (bypassing Discarding and Learning) and is intended for end-user edge devices.

Applying PortFast to switch-to-switch trunks risks immediate Layer 2 loops during topology changes.

Anahtar Kavram

Rapid PVST+ Port Roles and System ID Extension Rules

Tahmini Süre:1m 30s

Soru 1657Soru →

A network administrator is configuring a backup floating static route on router R3 to reach the remote destination network 192.168.50.0/24. The primary path to this network is dynamically learned via EIGRP with a default administrative distance of 90. The secondary path should route traffic through the next-hop IPv4 address 10.1.1.2.

Which TWO statements regarding this floating static route configuration are correct?

Geçerli olan tümünü seçin

The command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` correctly configures the backup route.

The floating static route will be installed into the active IPv4 routing table only when the primary EIGRP route is removed.

The command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 80` configures a floating static route that serves as a backup path.

Assigning an administrative distance of 90 to the static route enables equal-cost load sharing across the EIGRP and static paths.

Cevabı ve açıklamayı göster

Cevap: The command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` correctly configures the backup route.; The floating static route will be installed into the active IPv4 routing table only when the primary EIGRP route is removed.

Cevap

The correct choices are using the command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` and recognizing that the route is installed into the routing table only when the primary EIGRP route is removed.

To create a floating static route that backs up an EIGRP path (AD 90), the static route must be configured with an administrative distance greater than 90. The command specifying an AD of 100 correctly accomplishes this. As a result, the router holds the static route in reserve and only installs it into the active IPv4 routing table if the primary EIGRP route is withdrawn.

Adım Adım Çözüm

Identify the primary route's Administrative Distance (AD).

The primary path is learned via internal EIGRP, which has a default administrative distance of 90.

Floating static routes depend on AD ranking to remain inactive until the primary routing source drops.

Determine the required AD value for the floating static route.

The AD configured for the static route must be strictly greater than 90 (e.g., 100).

Cisco routers select routes with lower AD values for insertion into the active IPv4 routing table.

Evaluate the command syntax and routing behavior.

`ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` correctly assigns an AD of 100, ensuring the route stays dormant while EIGRP is active.

If the static route AD is set lower than 90 (such as 80), it preempts EIGRP and improperly acts as the primary path.

Anahtar Kavram

Floating Static Route Administrative Distance Selection

Soru 1658Soru →

An network administrator is troubleshooting an issue where client workstations attached to VLAN 20 (subnet 192.168.20.0/24) fail to receive IPv4 dynamic configuration settings from a centralized DHCP server located at 10.1.100.50 in VLAN 100. The administrator inspects the configuration on the Cisco IOS router acting as the default gateway for both subnets:

interface GigabitEthernet0/0/1.20
encapsulation dot1Q 20
ip address 192.168.20.1 255.255.255.0
!
interface GigabitEthernet0/0/1.100
encapsulation dot1Q 100
ip address 10.1.100.1 255.255.255.0
ip helper-address 10.1.100.50

Based on the router configuration output, why are the clients in VLAN 20 failing to obtain IP addresses from the DHCP server?

The ip helper-address command is configured on the router interface facing the DHCP server rather than on the incoming client gateway interface.

The router cannot relay DHCP broadcasts across subnets because routers inherently drop all Layer 2 and Layer 3 broadcast frames regardless of helper address configuration.

The ip helper-address configuration requires the addition of the overload keyword to enable unicast translation for cross-VLAN relay operation.

The subinterface GigabitEthernet0/0/1.20 requires the command ip dhcp relay information trust-all because Option 82 is inserted automatically whenever traffic crosses 802.1Q subinterfaces.

Cevabı ve açıklamayı göster

Cevap: The ip helper-address command is configured on the router interface facing the DHCP server rather than on the incoming client gateway interface.

Cevap

The ip helper-address command is configured on the router interface facing the DHCP server rather than on the incoming client gateway interface.

DHCP clients broadcast their DHCP Discover messages to 255.255.255.255. To relay these broadcasts to a unicast DHCP server in a different subnet, the 'ip helper-address' command must be configured on the router interface receiving those broadcasts (the client default gateway, GigabitEthernet0/0/1.20). In the provided configuration, the command was incorrectly placed on the subinterface facing the server (GigabitEthernet0/0/1.100), preventing the router from intercepting client requests.

Adım Adım Çözüm

Analyze client traffic flow and DHCP request behavior.

Clients in VLAN 20 send DHCP Discover packets as Layer 3 broadcasts (255.255.255.255) arriving on interface GigabitEthernet0/0/1.20.

DHCP clients do not initially have an IP address and broadcast their requests to locate a server.

Evaluate placement of the ip helper-address statement.

The ip helper-address 10.1.100.50 command is currently under GigabitEthernet0/0/1.100 instead of GigabitEthernet0/0/1.20.

The router listens for incoming broadcasts on the interface where the command is applied. Because it is absent on GigabitEthernet0/0/1.20, incoming broadcasts from VLAN 20 clients are discarded.

Formulate the correct configuration change.

Move ip helper-address 10.1.100.50 from subinterface .100 to subinterface .20.

Applying the helper address on GigabitEthernet0/0/1.20 allows the router to intercept client broadcasts, convert them to unicast packets directed to 10.1.100.50, and populate the giaddr field with 192.168.20.1 so the server selects the correct address pool.

Anahtar Kavram

DHCP Relay Agent Interface Placement and Operation

Soru 1659Soru →

Company router R1 currently reaches the remote subnetwork $192.168.50.0/24$ via internal EIGRP, which has a default Administrative Distance of 90. A network administrator wants to configure a backup floating static route to $192.168.50.0/24$ through the next-hop IP address 172.16.1.2. The floating route must remain inactive in the routing table until the primary EIGRP path becomes unavailable. Which Cisco IOS command correctly configures this floating static route?

ip route 192.168.50.0 255.255.255.0 172.16.1.2 95

ip route 192.168.50.0 255.255.255.0 172.16.1.2 85

ip route 192.168.50.0 255.255.255.0 172.16.1.2

ip route 192.168.50.0 255.255.255.0 172.16.1.2 90

Cevabı ve açıklamayı göster

Cevap: ip route 192.168.50.0 255.255.255.0 172.16.1.2 95

Cevap

The command 'ip route 192.168.50.0 255.255.255.0 172.16.1.2 95' correctly configures the floating static route.

A floating static route functions as a backup route by configuring an Administrative Distance (AD) higher than that of the primary routing source. Internal EIGRP has a default AD of 90. Configuring the static route with an AD of 95 ensures that Cisco IOS keeps the static route inactive in the routing table during normal conditions, activating it only if the primary EIGRP path fails.

Adım Adım Çözüm

Identify the Administrative Distance (AD) of the primary routing source.

Internal EIGRP has a default Administrative Distance of

90

Floating static routes rely on administrative distance values to determine primary vs. backup paths.

Determine the required Administrative Distance for the backup floating static route.

The administrative distance must be set to a value greater than

90

(such as

95

Cisco IOS prefers routes with lower administrative distance values. Setting a value higher than

90

keeps the static route out of the routing table while the EIGRP route is active.

Construct the static route CLI command including the destination IP, subnet mask, next-hop IP, and trailing AD parameter.

The resulting command is 'ip route 192.168.50.0 255.255.255.0 172.16.1.2 95'.

The trailing numeric argument defines the custom administrative distance for the static route.

Anahtar Kavram

Floating Static Route Configuration and Administrative Distance

Soru 1660Soru →

Two Cisco routers, R1 and R2, are directly connected via an Ethernet link and configured for OSPFv2 single-area routing. An administrator notices that the OSPF neighbor state between R1 and R2 remains continuously stuck in the EXSTART state. Which configuration mismatch is the most likely cause of this issue?

An IP Maximum Transmission Unit (MTU) mismatch on the interconnecting interfaces

Mismatched OSPF Hello or Dead timer intervals on the interface

Different OSPF Area IDs assigned to the connecting interfaces

Setting the OSPF interface priority to 0 on both routers

Cevabı ve açıklamayı göster

Cevap: An IP Maximum Transmission Unit (MTU) mismatch on the interconnecting interfaces

Cevap

An IP Maximum Transmission Unit (MTU) mismatch on the interconnecting interfaces causes OSPF neighbors to become stuck in the ExStart or Exchange state.

During the ExStart state of OSPFv2 neighbor formation, routers elect a Master and Slave to sequence Database Description (DBD) packets. Cisco routers validate the IP MTU header field in incoming DBD packets against their local interface MTU. If an MTU mismatch exists, the larger-MTU router drops the smaller-MTU router's DBD packets (or vice versa), keeping the neighbor process continuously stuck in ExStart/Exchange.

Adım Adım Çözüm

Analyze OSPF neighbor establishment states

Identify that Hello parameter mismatches (Area ID, Hello/Dead timers, Authentication, Subnet Mask) prevent initial Hello acceptance and stop adjacencies in Down or Init states.

Basic parameters must match before Database Description (DBD) packet exchange begins.

Examine the ExStart/Exchange neighbor state requirements

In ExStart state, routers negotiate master/slave roles using DBD packets. By default, Cisco routers verify that the IP MTU in received DBD packets does not exceed their local interface MTU.

If MTU sizes differ between interfaces, DBD packet exchanges fail or are dropped, leaving the neighbor relationship stuck in ExStart or Exchange.

Anahtar Kavram

OSPF Neighbor States and MTU Mismatch Troubleshooting

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