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Tüm alıştırma soruları

1987 soru

Tüm türler1,987Çoktan seçmeli1,020Çoklu seçim452Sayısal18Eşleştirme229Sıralama203Boşluk doldurma22Kısa cevap43
Soru 1541Soru →

A network engineer changes the OSPFv2 network type on a GigabitEthernet interface linking two Cisco routers from the default Broadcast type to Point-to-Point using the interface subcommand `ip ospf network point-to-point`.

Which two operational changes occur on this interface as a direct result of this modification? (Choose two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: OSPF bypasses Designated Router (DR) and Backup Designated Router (BDR) elections on the interface segment.; The interface switches from 224.0.0.6 to exclusively using 224.0.0.5 for all OSPF multicast communication.

Cevap

The two correct statements are that OSPF bypasses DR/BDR elections on the interface segment, and all OSPF multicast communication uses 224.0.0.5 instead of 224.0.0.6.
Configuring `ip ospf network point-to-point` on an Ethernet interface alters OSPF behavior so that DR/BDR elections are completely bypassed. Additionally, because there is no DR or BDR to listen on 224.0.0.6, all OSPF traffic on the link is directed to the All-OSPF-Routers multicast address 224.0.0.5.

Adım Adım Çözüm

1
Analyze DR/BDR election requirements for OSPF network types
Broadcast networks elect a DR and BDR to reduce adjacency overhead on multiaccess media. Point-to-Point networks connect exactly two routers, eliminating the need for DR/BDR roles.
On point-to-point links, routers establish a direct FULL adjacency with each other without intermediate election logic.
2
Evaluate multicast address usage across OSPF roles
On multiaccess broadcast networks, DROther routers send Link State Updates to 224.0.0.6 (AllDRouters), and the DR floods updates to 224.0.0.5 (AllSPFRouters). On Point-to-Point networks without a DR, all OSPF packets (Hellos, LSU, LSAck) are sent directly to 224.0.0.5.
Since 224.0.0.6 is reserved exclusively for communicating with Designated Routers, it is not used on point-to-point interfaces.
3
Verify timer and neighbor discovery behaviors for Point-to-Point media
Point-to-Point interfaces maintain 10-second Hello and 40-second Dead default timers (same as Broadcast) and continue using multicast for dynamic neighbor discovery.
Longer 30-second timers and manual static neighbor commands are characteristics of Non-Broadcast Multi-Access (NBMA) networks, not Point-to-Point networks.

Anahtar Kavram

OSPFv2 Network Types and DR/BDR Selection Traits
Tahmini Süre:2m 0s
Soru 1542Soru →

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router. Internal hosts on subnet 10.45.10.0/2410.45.10.0/24 connect to interface `GigabitEthernet0/0/0`, while interface `GigabitEthernet0/0/1` connects to the Internet Service Provider. Standard access list 10 has been configured with `access-list 10 permit 10.45.10.0 0.0.0.255`. Which TWO configurations are required on the router to correctly enable inside source PAT sharing the public IPv4 address of `GigabitEthernet0/0/1`?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: Execute `ip nat inside source list 10 interface GigabitEthernet0/0/1 overload` in global configuration mode.; Configure `ip nat outside` under interface configuration mode for `GigabitEthernet0/0/1`.

Cevap

The two required configurations are executing 'ip nat inside source list 10 interface GigabitEthernet0/0/1 overload' in global configuration mode and configuring 'ip nat outside' on interface GigabitEthernet0/0/1.
Configuring 'ip nat inside source list 10 interface GigabitEthernet0/0/1 overload' in global configuration mode combined with applying 'ip nat outside' to interface GigabitEthernet0/0/1 completes the mandatory steps to translate internal source traffic matching ACL 10 across the ISP interface using Port Address Translation.

Adım Adım Çözüm

1
Identify the required global configuration statement for interface-based PAT.
The command 'ip nat inside source list 10 interface GigabitEthernet0/0/1 overload' correctly binds ACL 10 to the WAN interface and specifies port overload.
The 'overload' keyword allows thousands of internal sockets to share the single IP address assigned to GigabitEthernet0/0/1 using distinct layer 4 port numbers.
2
Identify interface NAT boundary designations.
Interface GigabitEthernet0/0/0 requires 'ip nat inside', and external interface GigabitEthernet0/0/1 requires 'ip nat outside'.
Cisco IOS NAT routing decisions require explicit identification of which interfaces face the inside private network and which interface faces the outside public network.

Anahtar Kavram

Inside Source Port Address Translation (PAT) using an Interface
Soru 1543Soru →

A network administrator is connecting a Cisco Wireless LAN Controller (WLC) to an upstream Cisco Catalyst switch using multiple physical distribution system ports. To increase throughput and provide interface redundancy, the administrator enables Link Aggregation (LAG) on the controller. Which two configuration requirements must be met on the upstream switch to support proper EtherChannel operation with the WLC? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: All physical switch interfaces connected to the WLC distribution ports must be grouped into a single EtherChannel interface.; The switch ports connected to the WLC physical ports must be configured with identical attributes, including 802.1Q trunking mode and allowed VLAN lists.

Cevap

The upstream switch must group all physical interfaces connected to the controller into a single EtherChannel bundle, and all member switch ports must share identical trunking and VLAN configurations.
When Link Aggregation (LAG) is enabled on a Cisco Wireless LAN Controller, all physical distribution system ports are combined into a single logical link. Consequently, the connected upstream switch must aggregate all corresponding physical ports into a single matching EtherChannel (port-channel) group. Additionally, because EtherChannel bundle members must operate with consistent interface parameters, all participating switch ports must share identical configuration attributes, such as 802.1Q trunk mode and allowed VLAN lists.

Adım Adım Çözüm

1
Analyze WLC Link Aggregation (LAG) behavioral requirements.
Enabling LAG on a Cisco WLC merges all physical distribution system ports into a single logical link for load distribution and failover.
Because the controller treats all connected ports as one logical interface, the upstream switch must mirror this behavior by assigning all connected ports to a single switchport EtherChannel (port-channel) group.
2
Verify switchport trunking requirements for WLC infrastructure connections.
Member switch ports in an EtherChannel must match in configuration parameters (speed, duplex, 802.1Q trunking mode, and allowed VLANs).
Since WLC interfaces transport multiple VLANs corresponding to different SSIDs and management interfaces, the underlying port-channel and its physical member ports must be configured as 802.1Q trunks with consistent attributes.

Anahtar Kavram

WLAN Infrastructure Connections and Switch Link Aggregation (LAG)
Tahmini Süre:1m 30s
Soru 1544Soru →

An enterprise network engineer adds a new router, Core-GW3, to an existing OSPFv2 broadcast multiaccess Ethernet segment (172.16.10.0/24172.16.10.0/24) where Router-A (Router ID 1.1.1.11.1.1.1, Priority 100100) is currently acting as the Designated Router (DR) and Router-B (Router ID 2.2.2.22.2.2.2, Priority 100100) is acting as the Backup Designated Router (BDR).

The engineer issues the following command on Core-GW3:

text
Core-GW3# show ip ospf interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 172.16.10.3/24, Area 0
Process ID 1, Router ID 10.10.10.10, Network Type BROADCAST, Cost: 1
Enabled by interface configuration option
Transmit Delay is 1 sec, State DROTHER, Priority 0
Designated Router (ID) 1.1.1.1, Interface address 172.16.10.1
Backup Designated Router (ID) 2.2.2.2, Interface address 172.16.10.2
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5

If Router-A (the active DR) suddenly experiences a hardware failure and reboots, which role will Core-GW3 assume on this segment?

Cevabı ve açıklamayı göster

Cevap: Core-GW3 will remain in the DROTHER state and will not be elected as DR or BDR regardless of failures on the network.

Cevap

Core-GW3 will remain in the DROTHER state and will not be elected as DR or BDR regardless of failures on the network.
In OSPFv2 broadcast networks, the DR and BDR elections are determined first by the highest interface priority (default is 1, range is 0 to 255). A router interface configured with an OSPF priority of 0 is explicitly rendered ineligible to become either a DR or a BDR. Even if the current DR fails and even if Core-GW3 possesses the highest Router ID on the subnet (10.10.10.1010.10.10.10), its priority of 0 forces it to remain in the DROTHER state permanently.

Adım Adım Çözüm

1
Examine the output of the command 'show ip ospf interface GigabitEthernet0/0'.
Identify that Core-GW3 has an OSPF interface priority of 0 ('Priority 0') and a Router ID of 10.10.10.10.
OSPF DR/BDR elections evaluate interface priority values before looking at Router IDs.
2
Apply the OSPF DR/BDR election priority rules.
Determine that an interface priority value of 0 explicitly disqualifies a router from participating in DR/BDR elections.
Setting 'ip ospf priority 0' configures the router to remain permanently as a DROTHER on broadcast and non-broadcast multiaccess networks.
3
Evaluate the network event (failure of Router-A).
Router-B (the existing BDR) will be promoted to DR. A new BDR will be elected from eligible DROTHER routers with priority > 0. Core-GW3 remains DROTHER.
Core-GW3 cannot participate in the election for the replacement BDR despite having a high Router ID.

Anahtar Kavram

OSPF DR/BDR Election Ineligibility with Priority 0
Soru 1545Soru →

A network administrator is configuring Port Address Translation (PAT) on a Cisco IOS router to map internal host traffic matched by access list 1515 to the IPv4 address assigned to public WAN interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}. The inside and outside interfaces have already been designated using `ip nat inside` and `ip nat outside`, and `access-list 15 permit 172.16.10.0 0.0.0.255` is active. What exact Cisco IOS global configuration command must be entered to complete this Port Address Translation configuration?

Cevabı ve açıklamayı göster

Cevap: ip nat inside source list 15 interface GigabitEthernet0/0/1 overload; ip nat inside source list 15 interface gigabitethernet0/0/1 overload; ip nat inside source list 15 interface Gi0/0/1 overload; ip nat inside source list 15 interface gi0/0/1 overload

Cevap

ip nat inside source list 15 interface GigabitEthernet0/0/1 overload
The command `ip nat inside source list 15 interface GigabitEthernet0/0/1 overload` accurately references the designated access list (15), binds it to the specified egress WAN interface (GigabitEthernet0/0/1), and enables Port Address Translation using the `overload` keyword.

Adım Adım Çözüm

1
Identify the required NAT component structure
The command requires specifying inside source translation, matching traffic via access list 15, and linking to interface GigabitEthernet0/0/1.
Cisco IOS requires declaring the translation direction and source criteria.
2
Append the key Port Address Translation parameter
Add the keyword `overload` at the end of the command.
Without the `overload` keyword, Cisco IOS defaults to dynamic one-to-one NAT rather than Port Address Translation (many-to-one mapping using transport layer port numbers).

Anahtar Kavram

Inside Source PAT Configuration with Interface Overload
Tahmini Süre:1m 30s
Soru 1546Soru →

An engineer needs to configure two IPv6 static routes on a Cisco IOS router:
1. A static route to reach the remote network 2001:db8:3c0d:1::/642001:\text{db8}:3\text{c0d}:1::/64 using the link-local address fe80::1\text{fe80}::1 of the adjacent router connected via interface GigabitEthernet0/0/1\text{GigabitEthernet0/0/1}.
2. A backup (floating) default static route via the global unicast next-hop address 2001:db8:acad:f::12001:\text{db8}:\text{acad}:\text{f}::1 with an Administrative Distance of 130130.

Which TWO IPv6 static route commands correctly fulfill these requirements?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:3c0d:1::/64 GigabitEthernet0/0/1 fe80::1; ipv6 route ::/0 2001:db8:acad:f::1 130

Cevap

The two correct command statements are 'ipv6 route 2001:db8:3c0d:1::/64 GigabitEthernet0/0/1 fe80::1' and 'ipv6 route ::/0 2001:db8:acad:f::1 130'.
The correct command for the specific subnet prefix using a link-local address explicitly provides both the exit interface and the link-local address. The correct backup default route uses '::/0' with an administrative distance of 130, ensuring it functions as a floating static route.

Adım Adım Çözüm

1
Analyze link-local next-hop syntax requirements
Link-local addresses (fe80::/10) are non-routable outside the local link. Therefore, Cisco IOS requires the exit interface parameter when using a link-local next-hop (e.g., 'GigabitEthernet0/0/1 fe80::1').
Without the exit interface, the router cannot determine which outgoing interface leads to that link-local neighbor.
2
Identify default route prefix and floating static AD requirements
The IPv6 default route prefix is '::/0'. To make it floating/backup, its administrative distance must be set higher than the primary routing source (in this case, 130).
An AD of 130 ensures the route remains inactive in the routing table until primary routes with lower AD values fail.

Anahtar Kavram

IPv6 Static Route Syntax & Link-Local Next-Hop Requirements
Soru 1547Soru →

Match each OSPFv2 network type or interface state on the left with its correct DR/BDR election requirement and default timer characteristics on the right.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Broadcast Multiaccess interface with default interface settings
Point-to-Point interface over a serial link running HDLC
Ethernet interface configured with the command `ip ospf priority 0`
Point-to-Multipoint interface environment

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

Broadcast Multiaccess maps to electing DR/BDR with 10s/40s timers; Point-to-Point maps to no DR/BDR with 10s/40s timers; Interface priority 0 maps to election ineligibility (DROTHER); Point-to-Multipoint maps to no DR/BDR with 30s/120s timers.
Each OSPF interface network type specifies whether DR/BDR elections are held and sets default Hello/Dead timers. Broadcast Ethernet networks elect DR/BDR with 10s/40s timers. Point-to-Point links bypass DR/BDR elections with 10s/40s timers. Setting priority to 0 on a broadcast interface retains standard timers but prevents DR/BDR election. Point-to-Multipoint skips DR/BDR elections and uses 30s/120s default timers.

Adım Adım Çözüm

1
Analyze OSPF election requirements per network type
Broadcast networks elect DR/BDR; Point-to-Point and Point-to-Multipoint networks do not elect DR/BDR.
DR/BDR election is only required on multiaccess media (Broadcast and Non-Broadcast) to reduce link-state packet duplication.
2
Determine interface priority impact
Setting priority to 0 makes a router ineligible to become DR or BDR regardless of router ID.
OSPF interface priority ranges from 0 to 255, where 0 explicitly prevents candidacy.
3
Evaluate default Hello and Dead timers for each network type
Broadcast and Point-to-Point default to 10s/40s, while Point-to-Multipoint defaults to 30s/120s.
Non-broadcast and point-to-multipoint OSPF network types assume slower WAN links and use 30-second Hello / 120-second Dead timer defaults.

Anahtar Kavram

OSPFv2 DR/BDR election rules and default timer intervals vary according to the interface network type and priority setting.
Soru 1548Soru →

A network engineer is configuring OSPFv2 between two Cisco routers connected over an Ethernet link. Which TWO parameters must match between the routers for an OSPFv2 neighbor adjacency to form successfully? (Select TWO.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: OSPF Area ID; Hello and Dead timer intervals

Cevap

The OSPF Area ID and the Hello and Dead timer intervals must match between the connecting router interfaces.
For two OSPFv2 routers to establish an adjacency, several key Hello packet parameters must match identically: the Area ID, Hello and Dead timers, IP subnet mask, and authentication credentials. If the Area ID or timer values differ, the routers will remain unable to form a neighbor relationship.

Adım Adım Çözüm

1
Analyze OSPF Hello packet requirements for neighbor discovery
Identify parameters that are checked in received Hello packets before forming an adjacency.
OSPF routers inspect specific fields in incoming Hello packets to ensure network compatibility.
2
Evaluate mandatory matching parameters
Area ID, Hello/Dead timers, Subnet Mask, and Authentication parameters must match across the link.
Mismatches in Area ID or timers cause the routers to ignore or drop Hello packets from each other.
3
Evaluate non-matching or unique parameters
OSPF Process ID is local to the device and does not need to match. OSPF Router ID must be unique across routers.
Process ID is only used internally by IOS to distinguish OSPF instances, and duplicate Router IDs cause routing instability.

Anahtar Kavram

OSPFv2 Neighbor Adjacency Requirements
Tahmini Süre:1m 0s
Soru 1549Soru →

A Cisco router receives an IPv4 unicast packet and must select the best path from its routing table to forward the traffic. Arrange the steps in the correct sequential order that the router follows to evaluate candidate routes and make a forwarding decision.

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Cevabı ve açıklamayı göster

Cevap

The correct order of steps in router forwarding decision logic is: 1) Identify candidate routes that match the destination IP, 2) Select the route with the longest prefix match, 3) Compare Administrative Distance if equal-length prefix ties exist between different routing sources, and 4) Compare route metrics if equal-length prefix ties exist within the same routing protocol.
The forwarding engine follows a strict evaluation hierarchy: first, matching candidate routes are identified; second, Longest Prefix Match (LPM) filters for the most specific subnet mask; third, Administrative Distance breaks ties between routes of equal prefix length from different protocols; fourth, metric breaks ties between routes of equal prefix length from the same protocol.

Adım Adım Çözüm

1
Identify matching candidate routes
A set of candidate routing table entries whose subnet masks encompass the packet's destination IPv4 address is compiled.
The router must locate all possible valid routes for the target destination before applying selection logic.
2
Apply Longest Prefix Match (LPM)
The candidate route with the longest prefix length (most specific mask) is selected.
LPM is the fundamental decision rule in IPv4/IPv6 packet forwarding. Prefix specificity overrides Administrative Distance and metric entirely.
3
Evaluate Administrative Distance (AD)
If multiple routes have identical prefix lengths from different sources, the route with the lower AD value (e.g., static AD 1 vs OSPF AD 110) is chosen.
AD acts as a tie-breaker between different route origins when prefix lengths are equal.
4
Evaluate Route Metric
If multiple routes have identical prefix lengths from the same protocol, the path with the lowest metric is selected (or load-balanced if equal).
Metrics are protocol-specific cost values used to determine the best path among routes learned via the same routing protocol.

Anahtar Kavram

Router Forwarding Decision Hierarchy (LPM > AD > Metric)
Tahmini Süre:1m 30s
Soru 1550Soru →

An engineer initializes OSPFv2 process 10 on a Cisco router. At initialization, the router has active interfaces Loopback0 (IP address 10.10.10.10/3210.10.10.10/32) and GigabitEthernet0/0 (IP address 192.168.1.1/24192.168.1.1/24). No manual router ID is configured initially. Shortly after OSPF forms adjacencies, the engineer configures interface Loopback1 with IP address 172.16.50.1/32172.16.50.1/32 (up/up) and then executes the `router-id 1.1.1.1` command under the `router ospf 10` configuration prompt. Assuming the command `clear ip ospf process` has NOT been executed and the router has NOT been reloaded, what IP address is currently used as the active OSPF router ID?

Cevabı ve açıklamayı göster

Cevap: 10.10.10.10

Cevap

10.10.10.10
The active OSPF Router ID remains 10.10.10.10 because OSPF Router ID selection is non-preemptive. Upon initial process startup without a manual router ID, the router selected the highest IP address among operational loopback interfaces (10.10.10.10). Subsequent configuration changes—such as adding a loopback with a higher IP address or configuring the `router-id 1.1.1.1` command—do not alter the running OSPF Router ID until the OSPF process is restarted with `clear ip ospf process` or the router is reloaded.

Adım Adım Çözüm

1
Determine initial OSPF Router ID election
Since no manual router ID was configured at initialization, OSPF selected the highest IP address among active loopback interfaces, which was 10.10.10.10.
OSPF election order evaluates explicit manual router-id configuration first, followed by active loopback interface IPs, and finally active physical interface IPs.
2
Evaluate the effect of adding a new loopback interface
Adding Loopback1 with IP 172.16.50.1 does not alter the active OSPF Router ID.
OSPF Router ID selection is non-preemptive; once an OSPF process selects a router ID, it does not change dynamically when new interfaces come online.
3
Evaluate the effect of executing the manual `router-id 1.1.1.1` command without restarting the OSPF process
The active OSPF Router ID remains 10.10.10.10.
In Cisco IOS/IOS-XE, manually modifying the OSPF router ID takes effect only after the OSPF process is reset using `clear ip ospf process` or the router is reloaded.

Anahtar Kavram

OSPFv2 Router ID Non-Preemptive Election and Modification Behavior
Tahmini Süre:2m 0s
Soru 1551Soru →

A network administrator configures Port Address Translation (PAT) on a Cisco IOS router so that internal hosts on the 10.10.50.0/2410.10.50.0/24 network can access external services through WAN interface GigabitEthernet0/0/1. The access list and global translation rules are configured as follows:

text
access-list 105 permit ip 10.10.50.0 0.0.0.255 any
ip nat inside source list 105 interface GigabitEthernet0/0/1 overload

During testing, internal clients cannot access external websites, and running `show ip nat translations` produces no output. An inspection of the interface configuration reveals:

text
interface GigabitEthernet0/0/0
description LAN Gateway
ip address 10.10.50.1 255.255.255.0
!
interface GigabitEthernet0/0/1
description WAN Interface
ip address 203.0.113.2 255.255.255.252
ip nat outside

Which configuration step on the router is required to enable successful address translation for the internal clients?

Cevabı ve açıklamayı göster

Cevap: Apply the command `ip nat inside` under interface GigabitEthernet0/0/0.

Cevap

Apply the command `ip nat inside` under interface GigabitEthernet0/0/0.
For Cisco IOS NAT/PAT to process packets, interfaces connecting to internal networks must be explicitly configured with the `ip nat inside` command, and external-facing interfaces must be configured with `ip nat outside`. Because GigabitEthernet0/0/0 lacked `ip nat inside`, traffic entering from the LAN was routed normally without undergoing NAT evaluation.

Adım Adım Çözüm

1
Identify NAT domain boundaries on the router interfaces.
GigabitEthernet0/0/1 is configured with `ip nat outside`, but GigabitEthernet0/0/0 lacks the `ip nat inside` designation.
Cisco IOS Network Address Translation requires at least one inside interface and one outside interface to trigger packet translation upon traversing the NAT boundary.
2
Evaluate the global NAT statement and access list configuration.
The global command `ip nat inside source list 105 interface GigabitEthernet0/0/1 overload` correctly references ACL 105 and specifies interface overload (PAT).
The syntax of the global NAT translation rule and referenced ACL is accurate.
3
Determine the necessary interface configuration fix.
Enter interface configuration mode for GigabitEthernet0/0/0 and execute `ip nat inside`.
Designating GigabitEthernet0/0/0 as the inside NAT interface allows the router to recognize incoming LAN traffic subject to NAT.

Anahtar Kavram

Inside and Outside NAT Interface Boundaries
Soru 1552Soru →

A network administrator is configuring Network Address Translation (NAT) on a Cisco IOS router interface connected to the internal local area network (GigabitEthernet0/0). What exact Cisco IOS interface configuration command designates this interface as the internal side for NAT translation?

Cevabı ve açıklamayı göster

Cevap: ip nat inside

Cevap

ip nat inside
The command 'ip nat inside' is used in interface configuration mode on a Cisco IOS router to identify the interface connected to the private inside network. This designation is mandatory for the router to properly identify inbound traffic needing source translation.

Adım Adım Çözüm

1
Identify the requirement for designating the LAN-facing interface in Cisco IOS NAT configuration.
Recognize that NAT requires defining which interfaces are on the inside (internal LAN) and which are on the outside (WAN/Internet).
Cisco IOS NAT needs explicit interface direction tagging to determine where packets arrive from and where they are headed.
2
Determine the exact interface configuration mode command.
The command is 'ip nat inside'.
This command tags the specified interface as part of the internal network boundary.

Anahtar Kavram

Designating inside interface for Cisco IOS NAT/PAT configuration
Soru 1553Soru →

A Cisco router receives an IPv4 packet destined for a remote subnet. Place the operational steps performed by the router to evaluate IPv4 static routes and forward the packet into the correct sequential order from first to last.

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Cevabı ve açıklamayı göster

Cevap

The correct sequence of operations is: (1) Extract and inspect the destination IPv4 address from the incoming packet header, (2) Search the routing table for matching static routes and identify the candidate entry with the longest prefix match, (3) Evaluate Administrative Distance if multiple static routes exist for the identical network prefix, and (4) Encapsulate the packet into a Layer 2 frame and transmit it out the resolved exit interface toward the next hop.
When an IPv4 packet arrives on a Cisco router interface, the router inspects the destination IP address in the packet header. It then searches the routing table to find all matching network prefixes, selecting the entry with the longest prefix match (most specific mask). If there are multiple static routes configured for the exact same prefix length, the router breaks the tie by choosing the route with the lowest Administrative Distance. Finally, the router determines the exit interface/next-hop IP, rewrites the Layer 2 frame, and transmits the packet.

Adım Adım Çözüm

1
Packet Ingress & Header Inspection
The destination IPv4 address is read from the packet.
The router requires the target destination address to perform a routing table lookup.
2
Longest Prefix Match Selection
The routing table entry with the longest subnet mask matching the destination IP is selected.
Cisco IOS router forwarding logic prioritizes the most specific prefix match over less specific routes.
3
Administrative Distance Tie-Breaking
If multiple static routes exist for the exact same prefix, the route with the lowest Administrative Distance is used.
Administrative Distance ranks route believability when multiple routes exist for identical destination prefixes.
4
Layer 2 Encapsulation and Forwarding
The packet is encapsulated into the outbound Layer 2 frame format and sent out the exit interface.
Final forwarding requires rewriting Layer 2 headers for the outbound physical or logical link.

Anahtar Kavram

IPv4 Static Route Lookup and Forwarding Decision Logic
Soru 1554Soru →

A non-root Cisco Catalyst switch running Rapid PVST+ receives BPDUs on multiple interfaces connected to neighboring switches for VLAN 20. The switch must determine which of its interfaces will become the single Root Port for VLAN 20. Place the tie-breaking steps evaluated by Rapid PVST+ in the exact sequential order from first step evaluated to last step evaluated.

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Cevabı ve açıklamayı göster

Cevap

The correct order of tie-breaking evaluation for Rapid PVST+ Root Port selection is: 1. Lowest cumulative Root Path Cost, 2. Lowest Sender Bridge ID (BID), 3. Lowest Sender Port ID, 4. Lowest local Receiver Port ID.
Rapid PVST+ evaluates Root Port selection using a strict four-step tie-breaker hierarchy: 1. Lowest cumulative Root Path Cost, 2. Lowest Sender Bridge ID (BID), 3. Lowest Sender Port ID (neighbor's port priority and index), 4. Lowest Receiver Port ID (local port priority and index).

Adım Adım Çözüm

1
Identify the primary STP metric for Root Port selection.
The switch calculates total path cost by adding link costs to reach the Root Bridge. Lowest cumulative path cost is evaluated first.
STP prioritizes reaching the Root Bridge via the least costly path.
2
Apply the first tie-breaker if path costs are equal.
The switch evaluates the Sender Bridge ID (Bridge Priority + Extended System ID + MAC address) of the upstream neighbor switches.
Preferring the neighbor with the lowest Bridge ID ensures a deterministic loop-free structure.
3
Apply the second tie-breaker if path costs and neighbor BIDs are equal.
The switch checks the Sender Port ID (Port Priority + Port Number) advertised in the BPDU by the neighbor switch.
This differentiates multiple parallel links connecting to the exact same neighbor switch.
4
Apply the final tie-breaker if all upstream BPDU fields are identical.
The switch selects its own local interface with the lowest Port ID.
Local port ID is the final fallback when upstream BPDU data offers no difference.

Anahtar Kavram

Rapid PVST+ Root Port Tie-Breaking Sequence
Soru 1555Soru →

A network administrator configures OSPFv2 process 1 on router R4 without manually specifying an OSPF router ID. Prior to starting the OSPF process, R4 has the following operational interface statuses and IPv4 addresses:

- Loopback 0: 10.200.1.1/24 (Administratively Down, Line Protocol Down)
- Loopback 1: 172.16.5.1/24 (Up, Line Protocol Up)
- Loopback 2: 172.16.20.1/24 (Up, Line Protocol Up)
- GigabitEthernet 0/0: 192.168.1.254/24 (Up, Line Protocol Up)

What IPv4 address will R4 select as its OSPF Router ID?

Cevabı ve açıklamayı göster

Cevap: 172.16.20.1

Cevap

172.16.20.1
When OSPFv2 initializes without a manually configured router ID, it selects the highest IPv4 address among operational (up/up) loopback interfaces. Loopback 0 is ignored because it is administratively down. Between the remaining active loopback interfaces, 172.16.20.1 on Loopback 2 is higher than 172.16.5.1 on Loopback 1. Active loopbacks take absolute precedence over physical interfaces, so GigabitEthernet 0/0 is not evaluated.

Adım Adım Çözüm

1
Check for manual router-id configuration
No explicit router-id command is configured under OSPFv2 process 1.
Manual configuration is the highest priority in OSPF Router ID selection.
2
Identify eligible operational loopback interfaces
Loopback 0 is excluded because its interface state is administratively down. Loopback 1 (172.16.5.1) and Loopback 2 (172.16.20.1) are eligible because both are Up/Up.
OSPF election logic considers active (up/up) loopback interfaces next, prioritizing them over active physical interfaces.
3
Select the highest IP address among eligible loopback interfaces
172.16.20.1 is selected as the Router ID.
Between the two active loopbacks, 172.16.20.1 is numerically higher than 172.16.5.1. The physical interface address 192.168.1.254 is ignored because active loopback interfaces take precedence.

Anahtar Kavram

OSPFv2 Router ID Election Order
Soru 1556Soru →

A network administrator is connecting four physical distribution system ports of a Cisco AireOS Wireless LAN Controller to an upstream Cisco Catalyst switch. Link Aggregation (LAG) is enabled on the controller to increase bandwidth and provide redundancy. Which port-channel configuration must be applied to the upstream Catalyst switch interfaces?

Cevabı ve açıklamayı göster

Cevap: Configure all connected switch interfaces into a single port-channel group using static mode 'on' with 802.1Q trunking enabled.

Cevap

Configure all connected switch interfaces into a single port-channel group using static mode 'on' with 802.1Q trunking enabled.
When LAG is enabled on a Cisco AireOS Wireless LAN Controller, all physical distribution system ports are bundled into a single logical interface. The connected Cisco Catalyst switch must be configured with all corresponding physical ports in a single EtherChannel port-channel set to static mode 'on' and operating as an 802.1Q trunk.

Adım Adım Çözüm

1
Identify the Link Aggregation (LAG) characteristics supported on Cisco AireOS Wireless LAN Controllers.
AireOS controllers support LAG only as a single logical EtherChannel bundle across all distribution system ports, requiring static EtherChannel mode ('on') without dynamic negotiation protocols (LACP/PAgP).
The controller software architecture requires all physical DS ports to participate in a single static EtherChannel bundle.
2
Determine switchport encapsulation and trunking requirements for WLC connectivity.
The switchport interface connecting to the WLC LAG bundle must be an 802.1Q trunk port to transport management and WLAN VLAN traffic.
Wireless controllers handle multiple wireless networks mapped to separate 802.1Q VLAN tags.

Anahtar Kavram

WLAN Infrastructure Connections and WLC LAG Switch Configuration
Tahmini Süre:1m 30s
Soru 1557Soru →

A network administrator checks the OSPF status of a router interface connected to an Ethernet broadcast domain and observes the following output:

text
GigabitEthernet0/0 is up, line protocol is up
Internet Address 192.168.10.5/24, Area 0
Process ID 1, Router ID 10.1.1.5, Network Type BROADCAST, Cost: 1
State DROTHER, Priority 0
Designated Router (ID) 10.1.1.1, Interface address 192.168.10.1
Backup Designated router (ID) 10.1.1.2, Interface address 192.168.10.2

Based on this command output, what is the operational effect of configuring an OSPF priority of 0 on this interface?

Cevabı ve açıklamayı göster

Cevap: The router is completely excluded from participating in the DR and BDR election process on this multi-access segment.

Cevap

Setting the OSPF interface priority to 0 prevents the router from participating in DR/BDR elections on that segment, forcing it into the DROTHER state.
In OSPFv2 broadcast and non-broadcast multi-access networks, setting an interface's OSPF priority to 0 (via the `ip ospf priority 0` interface configuration command) renders that router completely ineligible to be elected as Designated Router (DR) or Backup Designated Router (BDR). The router will strictly maintain the DROTHER state on that segment.

Adım Adım Çözüm

1
Examine the output line showing interface priority and OSPF state
The interface displays 'State DROTHER, Priority 0'.
In OSPFv2, interface priority range is 0 to 255, where 1 is the default.
2
Apply the OSPF priority rules for DR/BDR election eligibility
An OSPF interface priority of 0 explicitly designates a router as non-candidate for DR and BDR roles.
Configuring 'ip ospf priority 0' ensures the router never assumes DR or BDR responsibilities, preserving control plane stability on specified nodes.

Anahtar Kavram

OSPF Interface Priority and Election Eligibility
Soru 1558Soru →

Refer to the following excerpt from a Cisco router's IPv4 routing table:

text
Codes: C - connected, S - static, D - EIGRP, O - OSPF
Gateway of last resort is 172.16.1.1 to network 0.0.0.0

D 10.140.0.0/16 [90/2172416] via 10.1.1.1, 00:04:12, GigabitEthernet0/0
O 10.140.32.0/19 [110/20] via 10.2.2.2, 00:12:35, GigabitEthernet0/1
S 10.140.32.0/24 [1/0] via 10.3.3.3
C 10.140.32.128/25 is directly connected, GigabitEthernet0/2

The router receives an IP packet addressed to 10.140.32.13510.140.32.135. Which path or next hop will the router select to forward this traffic?

Cevabı ve açıklamayı göster

Cevap: Interface GigabitEthernet0/2

Cevap

The router will forward the packet out interface GigabitEthernet0/2 because the route 10.140.32.128/25 has the longest matching prefix for destination host 10.140.32.135.
When an IPv4 router receives a packet, it compares the destination IPv4 address against all routes in its routing table. When multiple routes match the destination host, the router always selects the route with the longest prefix length (the most specific subnet mask). Destination 10.140.32.13510.140.32.135 falls within 10.140.32.128/2510.140.32.128/25 (usable range 10.140.32.12910.140.32.129 to 10.140.32.25410.140.32.254). Since /25/25 is more specific than /24/24, /19/19, and /16/16, the router forwards traffic out GigabitEthernet0/2.

Adım Adım Çözüm

1
Identify all matching routes for the destination address 10.140.32.135.
Matches found: 10.140.0.0/16, 10.140.32.0/19, 10.140.32.0/24, and 10.140.32.128/25.
The destination address falls within the address range of all four listed subnets.
2
Compare prefix lengths among the candidate routes.
Prefix lengths are /16, /19, /24, and /25.
Router forwarding logic relies on the Longest Prefix Match (LPM) rule prior to evaluating Administrative Distance or Metric.
3
Select the most specific route (/25 prefix).
The route 10.140.32.128/25 connected to GigabitEthernet0/2 is chosen.
A /25 subnet mask matches 25 continuous network bits, which is more specific than /24, /19, or /16.

Anahtar Kavram

Longest Prefix Match (LPM) Precedence
Soru 1559Soru →

A network administrator views the OSPFv2 status of interface GigabitEthernet0/0 on router R1:

text
R1# show ip ospf interface gigabitEthernet 0/0
GigabitEthernet0/0 is up, line protocol is up
Internet Address 10.10.10.1/24, Area 0
Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
State DROTHER, Priority 0
Designated Router (ID) 3.3.3.3, Interface address 10.10.10.3
Backup Designated router (ID) 2.2.2.2, Interface address 10.10.10.2

If the current Designated Router (Router ID 3.3.3.3) unexpectedly reboots and fails on this multiaccess segment, which behavior will R1 exhibit during the subsequent election process?

Cevabı ve açıklamayı göster

Cevap: R1 will remain in the DROTHER state and will not participate in the election for either the DR or BDR role.

Cevap

R1 will remain in the DROTHER state and will not participate in the election for either the DR or BDR role.
In OSPFv2 multiaccess networks, setting `ip ospf priority 0` on an interface makes that interface completely ineligible to participate in Designated Router (DR) or Backup Designated Router (BDR) elections. When the primary DR fails, the existing BDR (Router ID 2.2.2.2) promotes to DR, and a new BDR is elected only among other eligible routers with priority values of 1 to 255. Therefore, the router displaying priority 0 will remain in the DROTHER state throughout the election process.

Adım Adım Çözüm

1
Analyze the CLI output for interface priority.
Interface GigabitEthernet0/0 has 'Priority 0'.
In OSPFv2, the interface priority parameter dictates DR/BDR election eligibility.
2
Apply OSPF DR/BDR election rules for priority 0.
A router interface with an OSPF priority value of 0 is ineligible to become either DR or BDR.
Priority 0 is a explicitly defined mechanism to prevent a router interface from ever becoming a Designated Router or Backup Designated Router on broadcast or non-broadcast multiaccess networks.
3
Determine the state transition when DR fails.
The current BDR (Router ID 2.2.2.2) promotes to DR, and a new BDR election occurs among eligible routers (priority > 0). R1 remains DROTHER.
Because R1 is ineligible, it cannot be elected as BDR or DR during the promotion or re-election phase.

Anahtar Kavram

OSPF DR/BDR Election Ineligibility with Priority 0
Soru 1560Soru →

A network administrator needs to configure a one-to-one static Network Address Translation (NAT) mapping on a Cisco IOS router. The internal host with private IPv4 address 10.1.1.5010.1.1.50 must be statically translated to the public IPv4 address 198.51.100.50198.51.100.50. What exact Cisco IOS global configuration command should be entered to establish this static NAT mapping?

Cevabı ve açıklamayı göster

Cevap: ip nat inside source static 10.1.1.50 198.51.100.50; ip nat inside source static 10.1.1.50 198.51.100.50

Cevap

ip nat inside source static 10.1.1.50 198.51.100.50
The correct command syntax for establishing static NAT in Cisco IOS global configuration mode is `ip nat inside source static <inside-local-ip> <inside-global-ip>`. Substituting 10.1.1.5010.1.1.50 as the inside local IP and 198.51.100.50198.51.100.50 as the inside global IP yields `ip nat inside source static 10.1.1.50 198.51.100.50`.

Adım Adım Çözüm

1
Identify the static NAT command structure in Cisco IOS.
The static NAT syntax is `ip nat inside source static <local-ip> <global-ip>`.
Static NAT maps a specific inside local address to a specific inside global address.
2
Substitute the specified inside local IP address (10.1.1.5010.1.1.50) and inside global IP address (198.51.100.50198.51.100.50) into the command structure.
The complete command becomes `ip nat inside source static 10.1.1.50 198.51.100.50`.
This establishes a permanent one-to-one translation between the private IP address and public IP address.

Anahtar Kavram

Static Inside Source Network Address Translation (NAT) Configuration
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