Tüm alıştırma soruları

1987 soru

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

A network engineer is allocated the IPv4 address block $10.200.0.0/19$ to provision dedicated subnets for IP surveillance cameras across multiple industrial facilities. Each facility subnet must be configured using a $255.255.255.192$ subnet mask. How many distinct subnets can be created from this block?

Cevabı ve açıklamayı göster

Cevap: 128

Cevap

128 subnets can be created.

To determine the number of subnets created, convert the subnet mask

255.255.255.192

/26

CIDR notation. Borrowing bits from the original

/19

prefix yields

26 - 19 = 7

subnet bits. Calculating

2^7

gives exactly 128 subnets.

Adım Adım Çözüm

Determine the prefix length corresponding to the given subnet mask.

The dotted-decimal subnet mask

255.255.255.192

corresponds to a

/26

prefix (

24

network bits +

2

subnet bits in the fourth octet).

Converting the dotted-decimal mask to CIDR notation establishes the target prefix length.

Calculate the number of borrowed subnet bits.

26 \text{ bits (new prefix)} - 19 \text{ bits (original prefix)} = 7 \text{ borrowed subnet bits}

Subnetting extends the network prefix length from

/19

/26

Compute the total number of subnets.

2^7 = 128

total subnets.

The formula to calculate the number of subnets generated by borrowing

s

bits is

2^s

Anahtar Kavram

Subnet Count Calculation

Soru 1442Soru →

A network administrator initializes OSPFv2 on Router R1 when only interface GigabitEthernet0/0 (10.0.12.1/24) and Loopback 1 (172.31.1.1/24) are active. Later, the administrator performs two additional configuration changes on R1 without restarting the OSPF process:
1. Brings up Loopback 0 with IP address 10.254.254.1/32.
2. Configures `router-id 192.168.1.1` under the OSPF routing process.

Directly connected to R1's GigabitEthernet0/0 interface is Router R2 (10.0.12.2/24). R1's GigabitEthernet0/0 interface is assigned to OSPF Area 0, whereas R2's GigabitEthernet0/0 interface is configured for OSPF Area 1. Both routers share identical Hello/Dead timers and MTU settings.

Assuming no OSPF process resets have occurred, what is R1's active OSPF Router ID, and what neighbor relationship status will R1 report for R2?

R1's active Router ID is 172.31.1.1, and no OSPF neighbor entry is established for R2.

R1's active Router ID is 192.168.1.1, and the neighbor state is stuck in INIT.

R1's active Router ID is 10.254.254.1, and the neighbor state is stuck in 2-WAY.

R1's active Router ID is 172.31.1.1, and the neighbor state is stuck in EXSTART.

Cevabı ve açıklamayı göster

Cevap: R1's active Router ID is 172.31.1.1, and no OSPF neighbor entry is established for R2.

Cevap

R1's active Router ID remains 172.31.1.1, and no OSPF neighbor relationship is formed (no neighbor entry appears in R1's OSPF neighbor table).

OSPF Router ID election occurs when the OSPF process initializes. Once an active Router ID is chosen (in this case, 172.31.1.1 from the highest active loopback at process start), subsequent configuration changes—such as setting a manual 'router-id' or activating another loopback—do not alter the active Router ID until the OSPF process is explicitly reset via 'clear ip ospf process'. Furthermore, OSPF neighbor discovery requires matching Area IDs in Hello packets. Because R1 is in Area 0 and R2 is in Area 1, incoming Hello packets are dropped, resulting in no OSPF neighbor relationship being formed at all.

Adım Adım Çözüm

Determine R1's active OSPF Router ID.

R1 selected 172.31.1.1 upon OSPF initialization because Loopback 1 was the highest IP among active loopback interfaces.

OSPF Router ID election logic follows: manual 'router-id' > highest active loopback IP > highest active physical interface IP. However, Router ID election is non-preemptive. Adding a manual 'router-id' or bringing up a higher loopback IP (Loopback 0) later does NOT update the active Router ID until the process is restarted using 'clear ip ospf process' or a system reboot.

Evaluate the OSPF Hello packet exchange and neighbor adjacency conditions.

R1 (Area 0) and R2 (Area 1) have an Area ID mismatch in their OSPF Hello packet headers.

For two OSPFv2 routers to establish a neighbor relationship, key parameters in the Hello packet must match identically: Area ID, Subnet Mask, Hello/Dead Timers, Authentication, and Stub Area flag. If the Area ID mismatches, received Hello packets are silently discarded.

Determine the resulting OSPF neighbor state.

No neighbor state (or neighbor entry) exists.

Because Hello packets are dropped on receipt due to the Area ID mismatch, neither router discovers the other, preventing even the INIT state from being reached.

Anahtar Kavram

OSPFv2 Router ID Stability & Mandatory Hello Packet Adjacency Parameters

Soru 1443Soru →

An enterprise network administrator is allocated the IPv4 address block $172.16.48.0/21$ to provision subnets for multiple VLANs in a regional branch office. One specific VLAN requires support for at least $100$ host devices while maximizing address efficiency. Which subnetwork address and CIDR prefix pair represents a valid, correctly sized subnet within the assigned parent block?

172.16.50.0/25

172.16.50.0/26

172.32.50.0/25

172.16.56.0/25

Cevabı ve açıklamayı göster

Cevap: $172.16.50.0/25$

Cevap

The subnet address

172.16.50.0/25

is correct because it falls within the

172.16.48.0/21

parent block, uses valid RFC 1918 private addressing, and provides 126 usable host addresses.

The subnet

172.16.50.0/25

is correct because a

/25

prefix provides

2^7 - 2 = 126

usable host addresses, which satisfies the 100 host requirement efficiently. Furthermore,

172.16.50.0

lies well within the assigned parent block of

172.16.48.0/21

(range

172.16.48.0

172.16.55.255

) and belongs to valid RFC 1918 private IP space.

Adım Adım Çözüm

Determine the address range of the allocated parent block

172.16.48.0/21

The block has 21 network bits, leaving 11 host bits. The 3rd octet ranges from 48 (

00011000_2

) to 55 (

00011111_2

). The valid IP range is

172.16.48.0

through

172.16.55.255

Any valid subnets must fall strictly within these boundaries.

Calculate the minimum prefix length needed for at least 100 host devices.

Using

2^h - 2 \ge 100

, for

h=6

2^6 - 2 = 62

(insufficient). For

h=7

2^7 - 2 = 126

(sufficient). The required prefix length is

32 - 7 = 25

(

/25

Selecting

/25

provides enough host IPs while conserving space compared to a larger mask like

/24

Evaluate candidate

/25

subnets against the parent block boundaries and RFC 1918 rules.

172.16.50.0/25

starts at a valid

/25

boundary in the 4th octet (

0

), resides within the

172.16.48.0 - 172.16.55.255

range, and uses Class B RFC 1918 private space (

172.16.0.0/12

This confirms all sizing, allocation, and RFC standards are met.

Anahtar Kavram

IPv4 Subnet Sizing and RFC 1918 Boundary Analysis

Tahmini Süre:1m 30s

Soru 1444Soru →

A network engineer is selecting physical media and transceiver modules for an enterprise network expansion. Match each Ethernet interface standard or component on the left with its corresponding physical specification on the right.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

10GBASE-SR matches the 850 nm multimode fiber specification supporting up to 400 meters over OM4. 100BASE-FX matches the Fast Ethernet multimode fiber specification supporting up to 2 km. 10GBASE-T matches the Category 6A UTP copper requirement for 100-meter 10 Gbps links. SFP+ matches the hot-swappable 10 Gbps transceiver form factor.

Each physical media standard uniquely pairs with its physical medium, speed rating, and distance capability. 10GBASE-SR operates on 850 nm multimode fiber up to 400m over OM4; 100BASE-FX operates on Fast Ethernet multimode fiber up to 2 km; 10GBASE-T requires Category 6A UTP for 10 Gbps over 100 meters; SFP+ is the 10 Gbps transceiver module form factor.

Adım Adım Çözüm

Identify the optical wavelength and distance limits for 10 Gbps multimode fiber.

10GBASE-SR specifies 850 nm optics over multimode fiber reaching up to 300m on OM3 or 400m on OM4.

The 'SR' designation stands for Short Reach optical transmission.

Determine the distance specification for Fast Ethernet optical links.

100BASE-FX provides 100 Mbps speed over multimode fiber up to 2 km.

100BASE-FX extends Fast Ethernet reach beyond the 100-meter copper limit using multimode fiber.

Evaluate UTP copper cabling categories for 10 Gbps Ethernet.

10GBASE-T requires Category 6A UTP to achieve the full 100-meter distance limit.

Standard Category 6 is limited to 37–55 meters for 10GBASE-T due to alien crosstalk; Cat6A is needed for 100m.

Match the modular interface module type to its bandwidth capacity.

SFP+ is the enhanced modular form factor designed for 10 Gbps throughput.

Standard SFP modules support up to 1 Gbps, while SFP+ modules support 10 Gbps.

Anahtar Kavram

Ethernet Physical Layer Standards, Fiber/Copper Cabling Media Specifications, and Transceiver Form Factors

Soru 1445Soru →

A network engineer is configuring static routes on a Cisco IOS router to forward traffic to remote IPv6 networks. Which TWO statements accurately describe the requirements and behavior of IPv6 static route configurations? (Select TWO.)

Geçerli olan tümünü seçin

When specifying an IPv6 link-local address as the next-hop address, the local exit interface MUST also be specified in the command.

To configure a floating static IPv6 backup route, the administrative distance value must be set higher than the administrative distance of the primary route.

When using a global unicast address as the next hop, specifying the outbound exit interface is mandatory for the route to enter the IPv6 routing table.

A default IPv6 static route uses the prefix notation 0.0.0.0/0 followed by the next-hop IPv6 address.

Cevabı ve açıklamayı göster

Cevap: When specifying an IPv6 link-local address as the next-hop address, the local exit interface MUST also be specified in the command.; To configure a floating static IPv6 backup route, the administrative distance value must be set higher than the administrative distance of the primary route.

Cevap

The correct statements are: specifying the local exit interface is mandatory when using a link-local next-hop address, and configuring a floating static route requires an administrative distance higher than the primary route.

In Cisco IOS IPv6 static routing, link-local next-hop addresses require the specifying of the local exit interface because link-local addresses are ambient to the specific interface link. Furthermore, creating a backup (floating) static route requires setting an administrative distance value strictly higher than the primary route so it remains inactive until the primary path fails.

Adım Adım Çözüm

Analyze link-local next-hop requirements

Link-local addresses are non-routable outside their local segment, making the exit interface mandatory for path identification.

Without specifying the exit interface, the router cannot determine which local link connects to the link-local neighbor.

Analyze floating static route administrative distance mechanics

Setting a higher administrative distance keeps the static route out of the routing table until the primary route drops.

Lower administrative distance routes are preferred by the Cisco IOS routing table logic.

Anahtar Kavram

IPv6 Static Route Next-Hop Types and Administrative Distance Configuration

Soru 1446Soru →

Refer to the following partial IPv4 routing table output from a Cisco router:

text
Gateway of last resort is 192.168.1.1 to network 0.0.0.0

S* 0.0.0.0/0 [1/0] via 192.168.1.1, 5d12h, GigabitEthernet0/0/0
S 10.200.0.0/16 [1/0] via 192.168.14.2, 3d02h, GigabitEthernet0/0/3
D 10.200.45.0/24 [90/307200] via 192.168.13.2, 00:15:30, GigabitEthernet0/0/2
O 10.200.45.64/29 [110/20] via 192.168.12.2, 00:04:12, GigabitEthernet0/0/1

The router receives a packet with a destination IP address of $10.200.45.68$ . Which next-hop IP address and outbound interface will the router select to forward this packet?

192.168.12.2 via GigabitEthernet0/0/1

192.168.14.2 via GigabitEthernet0/0/3

192.168.13.2 via GigabitEthernet0/0/2

192.168.1.1 via GigabitEthernet0/0/0

Cevabı ve açıklamayı göster

Cevap: 192.168.12.2 via GigabitEthernet0/0/1

Cevap

The router forwards the packet to next-hop IP 192.168.12.2 via GigabitEthernet0/0/1.

When a router receives a packet, it compares the destination IP against all entries in its IP routing table and selects the match with the longest subnet mask (Longest Prefix Match). The subnet 10.200.45.64/29 covers IP addresses 10.200.45.64 through 10.200.45.71, which includes host 10.200.45.68. Because /29 is more specific than /24, /16, or /0, the router chooses next-hop 192.168.12.2 via GigabitEthernet0/0/1.

Adım Adım Çözüm

Identify all candidate routes that match destination IP 10.200.45.68

Matching routes: 0.0.0.0/0 (matches all), 10.200.0.0/16 (range 10.200.0.0-10.200.255.255), 10.200.45.0/24 (range 10.200.45.0-10.200.45.255), and 10.200.45.64/29 (range 10.200.45.64-10.200.45.71).

Before comparing administrative distance, the router identifies all routes whose network/prefix bounds contain the target IP.

Apply the Longest Prefix Match (LPM) rule across candidate routes

Prefix lengths are /0, /16, /24, and /29. The longest prefix match is /29.

The router always prioritizes the route with the most specific prefix (highest number of network bits).

Select the forwarding decision based on the winning route entry

The route for 10.200.45.64/29 points to next-hop 192.168.12.2 via interface GigabitEthernet0/0/1.

Administrative Distance is not evaluated across different prefix lengths, so the OSPF route /29 wins outright.

Anahtar Kavram

Longest Prefix Match Rule in Cisco IPv4 Forwarding Logic

Soru 1447Soru →

A network administrator needs to prevent wireless clients connected to the same SSID from communicating directly with each other at Layer 2 across the wireless controller. Which menu tab and feature configuration on the Cisco Wireless LAN Controller (WLC) GUI must be configured to achieve this client isolation?

Navigate to the Advanced tab under WLANs edit settings and set the Peer-to-Peer Blocking Action.

Navigate to the Security tab > Layer 3 sub-tab and enable Web Policy with Client Isolation.

Navigate to the General tab under WLANs edit settings and select Peer-to-Peer Isolation from the Radio Policy drop-down list.

Navigate to the QoS tab under WLANs edit settings and configure Traffic Stream Metrics (TSM) for Client Separation.

Cevabı ve açıklamayı göster

Cevap: Navigate to the Advanced tab under WLANs edit settings and set the Peer-to-Peer Blocking Action.

Cevap

Navigate to the Advanced tab under WLANs edit settings and set the Peer-to-Peer Blocking Action.

Peer-to-Peer Blocking is configured under the Advanced tab of a WLAN's configuration in the Cisco WLC GUI. It restricts connected wireless clients on the same WLAN from transmitting traffic directly to each other, enhancing network security.

Adım Adım Çözüm

Identify the required client isolation requirement.

The requirement is to prevent Layer 2 communications between clients associated with the same WLAN.

Peer-to-peer blocking stops wireless stations on the same subnet/WLAN from attacking or communicating directly with each other.

Locate the correct configuration menu in the Cisco WLC GUI.

Access WLANs > WLANs ID > Edit, then select the Advanced tab.

Advanced WLAN operational settings including Peer-to-Peer Blocking, AAA Override, and Coverage Hole Detection are grouped under the Advanced tab.

Select the appropriate Peer-to-Peer Blocking Action.

Choose Drop (or Up-Stream Forward depending on gateway design).

Setting the action to Drop drops peer-to-peer frames directly at the controller.

Anahtar Kavram

Cisco WLC Peer-to-Peer (P2P) Blocking configuration under WLAN Advanced tab

Tahmini Süre:1m 30s

Soru 1448Soru →

An network engineer is configuring a Cisco router interface using IPv6 link-local autoconfiguration. The burned-in MAC address of the interface is `0800.279f.a1b2`. Which IPv6 link-local address will be automatically generated for this interface using the EUI-64 standard?

fe80::a00:27ff:fe9f:a1b2

fe80::800:27ff:fe9f:a1b2

fe80::a00:27ff:ffff:a1b2

fe80::a00:279f:a1b2:fffe

Cevabı ve açıklamayı göster

Cevap: fe80::a00:27ff:fe9f:a1b2

Cevap

fe80::a00:27ff:fe9f:a1b2

The address fe80::a00:27ff:fe9f:a1b2 is correct because the EUI-64 process takes the MAC address 0800.279f.a1b2, inserts FFFE between the 24th and 25th bits (0800:27FF:FE9F:A1B2), and flips the 7th bit of the first byte from 0 to 1 (converting 08 to 0A). Combining this 64-bit interface ID with the FE80::/64 link-local prefix yields fe80::a00:27ff:fe9f:a1b2.

Adım Adım Çözüm

Split the 48-bit MAC address into two 24-bit halves.

Left half: 0800.27, Right half: 9f.a1b2

EUI-64 requires inserting a 16-bit payload into the center of the 48-bit hardware address.

Insert the hex string FFFE between the two halves.

0800:27FF:FE9F:A1B2

FFFE is the standard 16-bit sequence specified by IEEE EUI-64 calculation.

Invert the 7th bit (Universal/Local bit) of the first byte.

First byte 08 (hex 0000 0000 -> 0000 1000) becomes 0A (hex 0000 1010). Resulting Interface ID: 0A00:27FF:FE9F:A1B2 (shortened to a00:27ff:fe9f:a1b2).

Inverting the U/L bit indicates that the address is globally unique / universally administered.

Prepend the IPv6 link-local prefix FE80::/64 to the interface ID.

fe80::a00:27ff:fe9f:a1b2

IPv6 link-local addresses use the prefix FE80::/64 combined with the 64-bit EUI-64 interface identifier.

Anahtar Kavram

EUI-64 Interface Identifier Generation

Soru 1449Soru →

Two Cisco routers, R1 and R2, are directly connected over their GigabitEthernet0/0 interfaces in OSPFv2 Area 0. Interface GigabitEthernet0/0 on R1 has an IP address of $172.16.12.1/24$ with a default IP MTU of $1500$ bytes. Interface GigabitEthernet0/0 on R2 has an IP address of $172.16.12.2/24$ and its IP MTU has been modified to $1400$ bytes. Both routers successfully exchange Hello packets and recognize each other as neighbors, but the output of `show ip ospf neighbor` on R1 shows R2 perpetually stuck in the `EXSTART` state.

If the network administrator cannot alter the IP MTU size on either router interface, which configuration command must be configured under interface GigabitEthernet0/0 to allow the OSPF neighbor relationship to reach the `FULL` state?

Apply the `ip ospf mtu-ignore` command under the interface configuration mode on either or both routers.

Apply the `ip ospf hello-interval 10` command under the interface configuration mode on R2.

Reconfigure R2 with a higher OSPF Router ID using the `router-id 3.3.3.3` command under `router ospf` mode.

Configure `ip ospf network point-to-point` under the interface configuration mode on both connected interfaces.

Cevabı ve açıklamayı göster

Cevap: Apply the `ip ospf mtu-ignore` command under the interface configuration mode on either or both routers.

Cevap

The neighbor relationship can reach the FULL state by configuring the `ip ospf mtu-ignore` command on the interface with the MTU mismatch.

The correct option applies `ip ospf mtu-ignore` under interface configuration mode. When OSPF routers transition from 2-WAY to EXSTART, they negotiate Master/Slave roles and exchange Database Description (DBD) packets. Each router includes its interface MTU in the DBD packet. If there is an MTU mismatch, the router receiving the larger MTU value drops or ignores the DBD packet, keeping the adjacency stuck in EXSTART (or EXCHANGE). Executing `ip ospf mtu-ignore` forces OSPF to ignore the MTU value in incoming DBD packets, allowing the exchange to proceed to the FULL state.

Adım Adım Çözüm

Analyze the OSPF neighbor state

Neighbors reached the EXSTART state, confirming that Hello packet parameters (Area ID, Subnet Mask, Hello/Dead timers, Authentication) match.

Mismatched Hello parameters prevent neighbors from reaching 2-WAY or EXSTART entirely.

Identify the cause of the EXSTART state lockup

R1 has an IP MTU of

1500

bytes while R2 has an IP MTU of

1400

bytes.

During the EXSTART/EXCHANGE state, routers exchange Database Description (DBD) packets containing the interface MTU field. If a router receives a DBD packet specifying an MTU higher than its local interface MTU, it will reject the packet and remain stuck in EXSTART/EXCHANGE.

Select the appropriate mitigation command

Applying `ip ospf mtu-ignore` on the interface disables the MTU mismatch check during DBD negotiation.

This allows DBD packet processing to continue without modifying the physical or logical interface MTU values.

Anahtar Kavram

OSPF Neighbor Adjacencies and MTU Negotiation in ExStart State

Soru 1450Soru →

An administrator is troubleshooting an OSPFv2 adjacency issue between two directly connected Cisco routers, R1 and R2. Executing `show ip ospf neighbor` on R1 displays the neighbor state for R2 as stuck in `INIT/ -`. Which network condition or configuration error is the primary cause of this specific neighbor state?

An Access Control List (ACL) on R2 is filtering incoming OSPF Hello packets sent by R1, creating unidirectional communication.

The maximum transmission unit (MTU) size is mismatched on the connecting interfaces of R1 and R2.

The OSPF Hello and Dead interval timers are set to non-matching values on R1 and R2.

The connecting interfaces on R1 and R2 are assigned to different OSPF Area IDs.

Cevabı ve açıklamayı göster

Cevap: An Access Control List (ACL) on R2 is filtering incoming OSPF Hello packets sent by R1, creating unidirectional communication.

Cevap

An Access Control List (ACL) on R2 is filtering incoming OSPF Hello packets sent by R1, creating unidirectional communication.

The OSPF INIT state means a router has received a Hello packet from a neighbor, but the receiving router's own Router ID was not included in the neighbor's list of seen routers. This condition indicates one-way (unidirectional) communication. If an Access Control List on the remote router blocks incoming OSPF multicast or unicast traffic from the local router, the remote router will never record the local router's ID, causing the local router to remain stuck in the INIT state.

Adım Adım Çözüm

Analyze the reported OSPF neighbor state

The neighbor state is `INIT/ -`.

The INIT state signifies that R1 has successfully received OSPF Hello packets from R2, but R1's own Router ID was not listed in R2's Hello packet active neighbor list.

Evaluate the cause of unidirectional Hello reception

R2 is sending Hellos to R1 (which R1 receives), but R2 is not receiving Hellos from R1.

If an ACL on R2 drops R1's incoming Hellos, R2 never processes R1's Hello, so R2 does not add R1's Router ID to its outgoing Hello packets.

Distinguish INIT state causes from DOWN and EXSTART state causes

Parameter mismatches (Area ID, Hello/Dead timers, Authentication) cause packets to be dropped before reaching INIT (remaining DOWN). MTU mismatches cause neighbors to freeze in EXSTART/EXCHANGE.

Only unidirectional traffic flow (such as an ACL blocking traffic in one direction) allows Hello reception without mutual Router ID acknowledgment.

Anahtar Kavram

OSPFv2 Neighbor States and Unidirectional Communication Troubleshooting

Tahmini Süre:1m 30s

Soru 1451Soru →

An administrator needs to manually configure an IPv4 static route on a Cisco router to reach remote network $172.20.10.0/24$ using the next-hop IP address $10.0.0.2$ , and then permanently save the configuration. What is the correct sequence of steps to complete this configuration starting from Privileged EXEC mode?

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct order to enter global configuration mode, apply the static route command with the correct prefix, subnet mask, and next-hop IP, exit back to privileged EXEC mode, and save the active configuration to NVRAM is: Enter global configuration mode (`configure terminal`), Configure the static route (`ip route 172.20.10.0 255.255.255.0 10.0.0.2`), Return to privileged EXEC mode (`end`), and Save the configuration (`copy running-config startup-config`).

Configuring a persistent IPv4 static route on a Cisco router requires moving to global configuration mode via `configure terminal`, applying the static route with `ip route 172.20.10.0 255.255.255.0 10.0.0.2`, exiting back to privileged EXEC mode using `end`, and finally writing the running configuration to NVRAM using `copy running-config startup-config`.

Adım Adım Çözüm

Transition from Privileged EXEC mode (`Router#`) to Global Configuration mode (`Router(config)#`).

The router prompt changes to `Router(config)#`, allowing structural configuration commands.

Static routes cannot be defined directly in Privileged EXEC mode.

Issue the IPv4 static route command `ip route 172.20.10.0 255.255.255.0 10.0.0.2`.

The static route is added to the running configuration and installed into the IPv4 routing table.

Cisco IOS requires the syntax `ip route <prefix> <mask> <next-hop-ip|exit-interface>`.

Return to Privileged EXEC mode using `end` or `exit`.

The prompt reverts back to `Router#`.

File management and memory write commands must be issued from Privileged EXEC mode.

Write the active configuration from RAM to NVRAM using `copy running-config startup-config`.

The current running-config is saved to startup-config in NVRAM.

Without saving, configuration modifications will be lost if the device loses power or reboots.

Anahtar Kavram

Cisco IOS IPv4 Static Route CLI Configuration Workflow

Soru 1452Soru →

Match each OSPFv2 network type or interface configuration setting to its corresponding DR/BDR election behavior.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

Broadcast network type matches with electing a DR and BDR. Point-to-Point network type matches with not electing a DR or BDR. An OSPF interface priority set to 0 matches with ineligibility for DR/BDR election.

Broadcast network types require a Designated Router (DR) and Backup Designated Router (BDR) to minimize adjacency traffic across shared multiaccess segments. Point-to-Point network types connect only two routers, so DR and BDR elections are omitted completely. Configuring an OSPF interface priority of 0 excludes that router from participating in elections, forcing its role to DROTHER.

Adım Adım Çözüm

Identify the election requirement for multiaccess media.

Broadcast networks elect a DR and BDR to manage adjacencies.

Ethernet broadcast networks are multiaccess, requiring centralized LSA flooding via DR/BDR.

Identify the election requirement for point-to-point media.

Point-to-Point networks form full adjacencies directly between the two endpoints without electing a DR or BDR.

There are only two devices on a point-to-point link, so a DR/BDR role provides no architectural benefit.

Determine the effect of configuring priority 0.

Setting ip ospf priority 0 makes the interface ineligible to become a DR or BDR.

Priority 0 is specifically reserved in OSPF to ensure a router stays in the DROTHER state regardless of Router ID.

Anahtar Kavram

OSPF DR/BDR Election Mechanics and Interface Types

Tahmini Süre:45s

Soru 1453Soru →

Complete the Cisco IOS command below to configure a floating static route for destination network $10.40.15.0/24$ using next-hop IP address $192.168.254.2$ to serve as a backup for a primary route learned via Internal EIGRP (Administrative Distance 90), specifying an administrative distance of $130$ .

Aşağıdaki boşlukları doldurun

Router(config)# ip route 10.40.15.0 255.255.255.0

Cevabı ve açıklamayı göster

Cevap

The completed Cisco IOS configuration command is `ip route 10.40.15.0 255.255.255.0 192.168.254.2 130`.

In Cisco IOS, the syntax for a static route is `ip route <prefix> <mask> <next-hop-ip> [administrative_distance]`. Specifying `192.168.254.2` as the next-hop IP address and appending `130` configures a floating static route. Because 130 is higher than Internal EIGRP's administrative distance of 90, the router keeps this static route inactive in the routing table until the primary EIGRP route is removed.

Adım Adım Çözüm

Identify the target network prefix and network mask.

The target prefix is

10.40.15.0

and the subnet mask for

/24

255.255.255.0

Cisco IOS static route syntax requires the destination network prefix followed by its subnet mask.

Identify the next-hop IP address.

The next-hop IP address for the first blank is

192.168.254.2

Traffic destined for

10.40.15.0/24

over the backup link will be forwarded to this next-hop IP.

Determine the administrative distance value to make the static route floating.

The administrative distance for the second blank is

130

An administrative distance value greater than the primary routing protocol's AD (Internal EIGRP AD = 90) ensures the static route remains floating (inactive in the routing table) until the primary route fails.

Anahtar Kavram

Floating Static Route Configuration & Administrative Distance

Soru 1454Soru →

Two Cisco routers, R1 and R2, are connected via a direct GigabitEthernet link. R1 has been configured with an explicit OSPF router ID of 1.1.1.1. Router R2 has no explicit router ID configured under its OSPF process, but has the following active interfaces:
- Loopback0: 10.10.10.1/32 (up/up)
- Loopback1: 10.20.20.1/32 (up/up)
- GigabitEthernet0/0: 172.16.1.1/24 (up/up)

Which two conditions or behaviors accurately reflect the OSPFv2 Router ID selection and neighbor adjacency formation process between R1 and R2? (Select two.)

Geçerli olan tümünü seçin

Router R2 automatically selects 10.20.20.1 as its OSPF router ID because it is the highest IP address among active loopback interfaces.

Hello intervals, Dead intervals, Area IDs, and subnet masks must match between R1 and R2 for a neighbor relationship to form across the link.

Router R2 selects 172.16.1.1 as its router ID because active physical interface IP addresses take precedence over virtual loopback interfaces.

An MTU mismatch between R1 and R2 will block Hello packet exchange entirely, keeping the neighbor state permanently in DOWN.

Cevabı ve açıklamayı göster

Cevap: Router R2 automatically selects 10.20.20.1 as its OSPF router ID because it is the highest IP address among active loopback interfaces.; Hello intervals, Dead intervals, Area IDs, and subnet masks must match between R1 and R2 for a neighbor relationship to form across the link.

Cevap

The correct statements are that R2 automatically selects 10.20.20.1 as its router ID (highest IP address among active loopbacks), and that Hello intervals, Dead intervals, Area IDs, and subnet masks must match between the neighbors to establish adjacency.

Router ID selection follows a strict order: explicit 'router-id' command > highest active loopback IP > highest active physical interface IP. Since R2 has active loopback interfaces, 10.20.20.1 is selected as the highest loopback IP. Additionally, OSPF neighbor formation strictly requires matching Hello/Dead timers, Area ID, Subnet Mask, and Authentication flags in exchanged Hello packets.

Adım Adım Çözüm

Evaluate the OSPF Router ID election logic for R2

Since no explicit 'router-id' command exists, OSPF evaluates active loopbacks. Loopback1 (10.20.20.1) is higher than Loopback0 (10.10.10.1).

Loopback interfaces take precedence over physical interfaces, and the highest IPv4 address among loopbacks is chosen.

Evaluate mandatory OSPF Hello packet fields for neighbor adjacency

Hello timer, Dead timer, Area ID, Subnet Mask (on multiaccess/point-to-point), and authentication credentials must match in incoming Hello packets.

Mismatches in any of these primary Hello fields prevent routers from transitioning past the INIT state.

Analyze the impact of MTU mismatches

MTU is negotiated in DBD packets during ExStart state, not in initial Hello exchanges.

Hello packets are exchanged successfully despite MTU mismatches, but adjacency fails during database description synchronization.

Anahtar Kavram

OSPFv2 Router ID Precedence and Hello Packet Neighbor Adjacency Requirements

Tahmini Süre:2m 0s

Soru 1455Soru →

A network administrator is configuring a static route on a Cisco router using a link-local address (fe80::2) as the next hop to reach the remote network 2001:db8:10:20::/64. The local egress interface is GigabitEthernet0/0/1. Which Cisco IOS command correctly configures this route?

ipv6 route 2001:db8:10:20::/64 GigabitEthernet0/0/1 fe80::2

ipv6 route 2001:db8:10:20::/64 fe80::2

ip route 2001:db8:10:20::/64 GigabitEthernet0/0/1 fe80::2

ipv6 route 2001:db8:10:20::/64 fe80::2 GigabitEthernet0/0/1

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:10:20::/64 GigabitEthernet0/0/1 fe80::2

Cevap

The correct command is 'ipv6 route 2001:db8:10:20::/64 GigabitEthernet0/0/1 fe80::2'.

When configuring an IPv6 static route using a link-local next-hop address, Cisco IOS requires a fully specified static route where the local exit interface (GigabitEthernet0/0/1) is provided prior to the next-hop IPv6 address (fe80::2).

Adım Adım Çözüm

Identify the global configuration command syntax for IPv6 static routing.

The command structure must start with 'ipv6 route' followed by destination-prefix/prefix-length.

IPv6 static routes in Cisco IOS require the 'ipv6 route' keyword.

Determine the formatting requirements for link-local next-hop addresses.

Because link-local addresses (FE80::/10) are reused across multiple links, the router requires a fully specified route that includes the local exit interface before the link-local next-hop address.

Without specifying the exit interface, Cisco IOS rejects the link-local next hop as ambiguous.

Anahtar Kavram

Fully Specified IPv6 Static Routes using Link-Local Next-Hop Addresses

Soru 1456Soru →

A network administrator is configuring Rapid PVST+ on a Cisco Catalyst switch to optimize Spanning Tree Protocol (STP) operations for VLAN 30. The administrator wants to manually set the bridge priority so that this switch becomes a predictable root bridge for VLAN 30. Which command will be successfully accepted by Cisco IOS CLI without returning a configuration error?

spanning-tree vlan 30 priority 20480

spanning-tree vlan 30 priority 18000

spanning-tree vlan 30 priority 20510

spanning-tree vlan 30 priority portfast

Cevabı ve açıklamayı göster

Cevap: spanning-tree vlan 30 priority 20480

Cevap

The command 'spanning-tree vlan 30 priority 20480' is valid because priority values must be specified in increments of 4096.

The correct answer specifies a base priority value (

20480

) that is a valid multiple of 4096 (

5 \times 4096

). In Cisco switches running Rapid PVST+, the Bridge ID uses a 4-bit priority field and a 12-bit System ID Extension containing the VLAN number. Consequently, configured priority values must be multiples of 4096.

Adım Adım Çözüm

Analyze the IEEE 802.1t / Rapid PVST+ Bridge Identifier (BID) structure.

The 8-byte BID consists of a 2-byte Bridge Priority (4-bit Priority + 12-bit System ID Extension) and a 6-byte MAC Address.

Because the 4 highest bits represent the configurable priority, valid CLI priority values can only change in steps of

2^{12} = 4096

Evaluate the mathematical validity of the priority values.

20480 / 4096 = 5.0

, which is a whole integer.

18000 / 4096 = 4.3945

, which is invalid.

Cisco IOS enforces priority inputs to be strictly in multiples of 4096 (

0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768

, etc.).

Verify System ID Extension behavior.

The administrator specifies the base priority (

20480

), and the switch automatically adds the VLAN ID (

30

) to form a priority of

20510

in BPDU frames.

Entering

20510

manually in the CLI is rejected because the CLI expects only the un-extended base priority value.

Anahtar Kavram

Rapid PVST+ System ID Extension and Bridge Priority Calculation

Soru 1457Soru →

A network engineer is configuring interface GigabitEthernet0/8 on a Cisco Catalyst switch to connect a security IP camera. The requirements specify creating a new VLAN named CAMERAS with VLAN ID 65 and configuring the interface as a static access port assigned to this VLAN. Which sequence of Cisco IOS commands correctly completes this configuration from global configuration mode?

vlan 65
name CAMERAS
exit
interface gigabitethernet0/8
switchport mode access
switchport access vlan 65

vlan 65
name CAMERAS
interface gigabitethernet0/8
switchport access vlan 65

interface gigabitethernet0/8
switchport mode access
switchport trunk native vlan 65
name CAMERAS

vlan CAMERAS
id 65
exit
interface gigabitethernet0/8
switchport mode dynamic desirable

Cevabı ve açıklamayı göster

Cevap: vlan 65
name CAMERAS
exit
interface gigabitethernet0/8
switchport mode access
switchport access vlan 65

Cevap

The correct command sequence creates VLAN 65, assigns it the name CAMERAS, and provisions interface GigabitEthernet0/8 using 'switchport mode access' and 'switchport access vlan 65'.

Proper Cisco IOS VLAN and access port configuration requires instantiating the VLAN with 'vlan <vlan-id>' in global configuration mode, naming it with 'name <name>', returning to global configuration mode, entering the target interface configuration context, explicitly defining static access mode with 'switchport mode access', and binding the port to the specified VLAN using 'switchport access vlan <vlan-id>'.

Adım Adım Çözüm

Create and name the VLAN in global configuration mode

VLAN 65 is instantiated with the name CAMERAS using 'vlan 65' followed by 'name CAMERAS'.

VLANs must be instantiated in the VLAN database to segment broadcast domains.

Enter interface configuration mode for GigabitEthernet0/8

The CLI prompt changes to switch(config-if)#.

Port assignment commands must be executed under the specific interface configuration context.

Set static access mode and assign the port to VLAN 65

Executing 'switchport mode access' disallows dynamic trunking, and 'switchport access vlan 65' places the interface in VLAN 65.

Explicitly setting access mode disables Dynamic Trunking Protocol (DTP) negotiation and locks the port into access operation.

Anahtar Kavram

VLAN Creation and Access Port Assignment Syntax

Soru 1458Soru →

Four candidate routers are connected to a shared multiaccess Ethernet segment to participate in an OSPFv2 Designated Router (DR) election. Arrange the evaluation criteria in order of precedence, starting with the primary criterion checked first at the top down to the final fallback tie-breaker at the bottom.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct order of precedence for OSPF DR election tie-breaking is: 1) Highest OSPF interface priority setting, 2) Highest manually configured OSPF router ID, 3) Highest IPv4 address on an active loopback interface, and 4) Highest IPv4 address on an active physical interface.

The Designated Router election first evaluates the interface priority configured on the multiaccess segment. If priorities tie, OSPF resolves the election using the router's Router ID (RID). The RID is determined in order by: 1) explicit manual configuration via 'router-id', 2) highest IP address on an active loopback interface, and 3) highest IP address on an active physical interface.

Adım Adım Çözüm

Evaluate segment interface priority

Highest interface priority wins the election (priority 0 disqualifies a router from becoming DR/BDR).

Interface priority (configured via 'ip ospf priority') is the top-level override mechanism for DR selection.

Check for explicit OSPF Router ID

If interface priorities tie, OSPF compares Router IDs, prioritizing a manually configured 'router-id'.

Manual Router ID configuration under the 'router ospf' process overrides dynamic interface IP selection.

Check active loopback interfaces

If no manual router ID is present, the highest IPv4 address on an active loopback interface is chosen as the Router ID.

Loopback interfaces offer stability over physical interfaces because they do not rely on physical link state.

Check active physical interfaces

If no loopback interfaces exist, the highest IPv4 address on an up/up physical interface becomes the Router ID.

This serves as the final dynamic tie-breaker for establishing the OSPF Router ID when no explicit or loopback settings exist.

Anahtar Kavram

OSPFv2 DR/BDR Election Precedence and Router ID Selection Criteria

Tahmini Süre:1m 0s

Soru 1459Soru →

Two directly connected Cisco routers, R1 and R2, are configured for OSPFv2 on their GigabitEthernet0/0 interfaces. Router R1 has its interface configured in OSPF Area 0, while Router R2 has its connecting interface configured in OSPF Area 1. All physical interfaces and IP subnet parameters are operating correctly.

What is the expected OSPF neighbor outcome between R1 and R2?

The routers will fail to establish an OSPF neighbor relationship because Area IDs in Hello packets must match.

The routers will form a 2-Way neighbor state, but they will fail to exchange routing tables and reach Full state.

The routers will successfully form a Full adjacency as long as both routers use the same OSPF Process ID.

The routers will form a Full neighbor adjacency only after a Designated Router (DR) is elected on the link.

Cevabı ve açıklamayı göster

Cevap: The routers will fail to establish an OSPF neighbor relationship because Area IDs in Hello packets must match.

Cevap

The routers will fail to establish an OSPF neighbor relationship because Area IDs in Hello packets must match.

For two routers to form an OSPFv2 neighbor relationship, specific fields in their Hello packets must match exactly on the interconnecting link. These required matching parameters include the Area ID, Subnet Mask, Hello and Dead intervals, Primary IP Subnet, Authentication credentials, and Stub Area flag. Because R1 is configured in Area 0 and R2 is configured in Area 1, their Hello packets will be dropped by the receiving interfaces, and no neighbor relationship will be established.

Adım Adım Çözüm

Analyze OSPF Hello packet matching requirements for neighbor adjacency.

Identify that the Area ID field is a mandatory matching parameter in OSPFv2 Hello packets.

For two routers to establish any OSPF neighbor state (starting from Init), primary parameters in the Hello packet must match exactly.

Compare the interface configuration settings of R1 and R2.

R1 is in Area 0 and R2 is in Area 1.

The Area IDs on the interconnecting link are mismatched.

Determine the impact of the Area ID mismatch on neighbor discovery.

R1 drops Hello packets received from R2 (and vice versa), preventing neighbor formation completely.

When a router receives an OSPF Hello packet with a mismatched Area ID, it drops the packet without adding the sending router to its neighbor table.

Anahtar Kavram

OSPFv2 Neighbor Adjacency Requirements

Soru 1460Soru →

An administrator is troubleshooting OSPFv2 neighbor connectivity between Router A and Router B connected directly over a GigabitEthernet broadcast segment. Both routers are configured in OSPF Area 0.

Router A has the following operational status:
- Loopback0 interface IP: 172.16.1.1/24 (Up/Up)
- Loopback1 interface IP: 192.168.100.1/24 (Up/Up)
- GigabitEthernet0/1 interface IP: 10.1.12.1/24 (Up/Up)
- Ten minutes after the OSPF process initialized, the administrator executed `router-id 1.1.1.1` under `router ospf 1`, but did not restart the OSPF process.
- An inbound IPv4 ACL applied to GigabitEthernet0/1 permits IP unicast traffic from Router B, but drops all IP multicast traffic addressed to 224.0.0.5.

Router B has the following operational status:
- Loopback0 interface IP: 10.2.2.2/32 (Up/Up)
- GigabitEthernet0/1 interface IP: 10.1.12.2/24 (Up/Up)
- Active OSPF Router ID: 10.2.2.2

When executing `show ip ospf neighbor` on Router B, the neighbor state for Router A is listed as `INIT/ -`. However, executing `show ip ospf neighbor` on Router A displays no output.

Which statement accurately explains why Router B is in the INIT state while Router A shows no neighbor, and identifies the Router ID that Router B receives from Router A?

Router B receives outgoing multicast Hellos from Router A containing Router ID 192.168.100.1 and moves Router A into the INIT state; Router A displays no neighbor because its inbound ACL drops Router B's multicast Hello packets.

Router B receives outgoing multicast Hellos from Router A containing Router ID 1.1.1.1 because the router-id command updates the active Router ID immediately, but Router A remains in DOWN state due to an Area ID mismatch.

Router B receives outgoing multicast Hellos from Router A containing Router ID 172.16.1.1 because Loopback0 is preferred over Loopback1, while Router A shows no neighbor because both routers have a DR priority of 0.

Router B receives outgoing multicast Hellos from Router A containing Router ID 10.1.12.1 because physical interfaces supersede loopback interfaces, but Router A fails to recognize Router B due to mismatched Hello timers.

Cevabı ve açıklamayı göster

Cevap: Router B receives outgoing multicast Hellos from Router A containing Router ID 192.168.100.1 and moves Router A into the INIT state; Router A displays no neighbor because its inbound ACL drops Router B's multicast Hello packets.

Cevap

The correct statement identifies that Router A's active Router ID is 192.168.100.1 (the highest active loopback IP address at startup, because the `router-id` command is non-preemptive until the OSPF process is cleared). Router B receives Router A's multicast Hello packets containing this Router ID and transitions Router A to the INIT state because Router B is not yet listed in Router A's Hello neighbor field. Meanwhile, Router A receives zero Hello packets from Router B because its inbound ACL filters all multicast traffic to 224.0.0.5, causing Router A to remain in the DOWN state with no neighbor table entries.

Adım Adım Çözüm

Determine Router A's active OSPF Router ID

Router A's active Router ID is 192.168.100.1.

When OSPF initializes without an explicit command, the router selects the highest IP address among active loopback interfaces. Loopback1 (192.168.100.1) is higher than Loopback0 (172.16.1.1). The `router-id 1.1.1.1` command was entered later but is non-preemptive; it requires `clear ip ospf process` or a reload to take effect.

Analyze outbound Hello packet transmission from Router A to Router B

Router B receives Router A's Hello packet containing Router ID 192.168.100.1.

Router A sends multicast Hello packets to 224.0.0.5 out GigabitEthernet0/1. Since Router A hasn't received Hellos from Router B yet, Router B's Router ID is not listed in the neighbor field of Router A's Hello packet.

Analyze Router B's state transition upon receiving Router A's Hello

Router B transitions Router A to the INIT state.

When a router receives a valid Hello packet from a neighbor that does not yet list the receiving router's own Router ID, it places that neighbor into the INIT state.

Analyze inbound packet processing on Router A

Router A drops Router B's multicast Hello packets (224.0.0.5) and shows no neighbor entry.

Router B responds by sending multicast Hellos to 224.0.0.5 containing Router A's Router ID in its neighbor list. However, Router A's inbound ACL drops all traffic to 224.0.0.5. As a result, Router A never receives Router B's Hellos, remains in the DOWN state, and displays no output for `show ip ospf neighbor`.

Anahtar Kavram

OSPFv2 Router ID election precedence (manual command requiring process reset vs. highest active loopback) combined with unidirectional Hello packet flow causing one-sided INIT neighbor states.

Tahmini Süre:3m 0s

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