Examkin

IP Connectivity

493 soru

Tüm türler493Çoktan seçmeli250Çoklu seçim113Eşleştirme25Sıralama60Boşluk doldurma22Kısa cevap23
Soru 321Soru →

An engineer configures a static backup route on router R1 for remote destination subnet 172.22.50.0/24172.22.50.0/24. The primary path to this subnet is learned dynamically via OSPFv2. During baseline verification, the engineer discovers that traffic destined for 172.22.50.0/24172.22.50.0/24 routes over the backup WAN circuit even though the primary OSPF link is active and in the FULL state. Which configuration issue on router R1 explains why the backup route is active in the routing table?

Cevabı ve açıklamayı göster

Cevap: The static route was configured without specifying a custom administrative distance, causing it to use the default administrative distance of 1, which beats the OSPF administrative distance of 110.

Cevap

The static route was configured without specifying a custom administrative distance, causing it to use the default administrative distance of 1, which beats the OSPF administrative distance of 110.
In Cisco IOS, static routes configured without an explicit administrative distance inherit the default value of 1. Because routers populate the IP routing table by choosing the path with the lowest administrative distance when multiple sources report the same prefix, a static route with AD 1 will take precedence over an OSPF route with AD 110. To act as a floating static route, the static route's administrative distance must be manually set higher than the primary routing protocol's AD (for example, setting AD to 115 or 120).

Adım Adım Çözüm

1
Identify the administrative distance (AD) of the primary dynamic routing protocol.
OSPFv2 has a default administrative distance of 110.
Administrative distance measures the trustworthiness of a routing source. Lower values are preferred.
2
Analyze default static route behavior when no administrative distance parameter is specified.
Cisco IOS assigns a default administrative distance of 1 to static routes.
Because 1 is lower than 110, the router chooses the static route as more believable than the OSPF route.
3
Determine the requirement for a floating static route.
To float behind OSPF, the static route must be configured with an administrative distance strictly greater than 110 (e.g., 120).
Omitting the AD parameter causes the static route to become the active primary path instead of a floating backup.

Anahtar Kavram

Floating Static Route Administrative Distance Configuration
Tahmini Süre:2m 0s
Soru 322Soru →

An administrator executes the `show ip route` command on a Cisco enterprise router, resulting in the following partial routing table output:

text
Codes: C - connected, S - static, O - OSPF, D - EIGRP

Gateway of last resort is not set

10.250.0.0/16 is variably subnetted, 4 subnets, 4 masks
O 10.250.16.0/20 [110/20] via 192.168.1.2, 00:14:22, GigabitEthernet0/0
D 10.250.16.0/24 [90/307200] via 192.168.1.6, 00:05:10, GigabitEthernet0/1
S 10.250.16.128/26 [1/0] via 192.168.1.10
C 10.250.16.128/27 is directly connected, GigabitEthernet0/2

Which two statements accurately describe how the router interprets these components and forwards traffic? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: A packet destined for 10.250.16.130 is egressed via GigabitEthernet0/2 because it matches the route with the longest prefix length (/27).; The bracketed output [90/307200] specifies an Administrative Distance of 90 and a routing metric of 307200 for the EIGRP-learned subnet.

Cevap

Packets for 10.250.16.130 match the /27 route out GigabitEthernet0/2 due to the longest prefix match rule, and the bracketed entry [90/307200] defines Administrative Distance as 90 and Metric as 307200.
When forwarding an IP packet, the router selects the route that matches the destination IP address with the longest prefix length (most specific subnet mask). Destination 10.250.16.130 fits within 10.250.16.128/27, which is a longer prefix than /26, /24, or /20, making GigabitEthernet0/2 the correct egress path. Additionally, Cisco IOS displays administrative distance and metric formatted as [Administrative Distance/Metric], meaning [90/307200] denotes an AD of 90 and a metric of 307200.

Adım Adım Çözüm

1
Evaluate destination IP 10.250.16.130 against all matching prefix ranges in the routing table.
10.250.16.130 falls into 10.250.16.0/20, 10.250.16.0/24, 10.250.16.128/26, and 10.250.16.128/27.
The router determines all candidates that enclose the destination IP address.
2
Apply the Longest Prefix Match (LPM) rule to select the best forwarding path among matching routes.
The subnet 10.250.16.128/27 has the longest prefix length (/27 > /26 > /24 > /20) and is chosen, forwarding the packet out GigabitEthernet0/2.
Longest prefix match always takes precedence over administrative distance or metric when forwarding IP traffic.
3
Decode the standard Cisco IOS bracketed routing table fields [AD/Metric].
For [90/307200], 90 is the Administrative Distance (EIGRP internal default) and 307200 is the EIGRP composite metric.
In Cisco IOS output format [X/Y], the first integer represents Administrative Distance and the second integer represents the protocol metric.

Anahtar Kavram

Routing Table Interpretation and Longest Prefix Match Forwarding Logic
Soru 323Soru →

Match each OSPFv2 network type on the left with its corresponding DR/BDR election behavior, neighbor discovery method, and default Hello/Dead timers on the right.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Broadcast
Point-to-Point
Point-to-Multipoint
Non-Broadcast Multi-Access (NBMA)

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

Broadcast pairs with DR/BDR election, dynamic multicast discovery, and 10s/40s timers. Point-to-Point pairs with suppressed DR/BDR election, dynamic multicast discovery, and 10s/40s timers. Point-to-Multipoint pairs with suppressed DR/BDR election, dynamic multicast discovery, and 30s/120s WAN timers. NBMA pairs with DR/BDR election, manual unicast neighbor configuration, and 30s/120s WAN timers.
The matching correctly pairs each OSPF network type with its operational attributes: Broadcast requires DR/BDR and uses 10s/40s timers with dynamic discovery; Point-to-Point bypasses DR/BDR and uses 10s/40s timers with dynamic discovery; Point-to-Multipoint bypasses DR/BDR but uses 30s/120s WAN timers with dynamic discovery; NBMA requires DR/BDR, 30s/120s WAN timers, and manual unicast neighbor definitions.

Adım Adım Çözüm

1
Analyze DR/BDR election requirements for each OSPF network type.
Broadcast and NBMA network types elect a DR/BDR. Point-to-Point and Point-to-Multipoint network types suppress DR/BDR elections.
DR/BDR elections are required on multi-access network types where all routers can reach each other directly to prevent n(n−1)/2n(n-1)/2 full adjacencies.
2
Determine neighbor discovery capabilities (Multicast vs. Unicast).
Broadcast, Point-to-Point, and Point-to-Multipoint dynamically discover neighbors using multicast address 224.0.0.5. NBMA requires manual unicast neighbor configuration.
Non-broadcast networks lack native multicast capability, requiring the administrator to manually define neighbor IP addresses under the OSPF router process.
3
Evaluate default OSPF Hello and Dead timers for each network type.
High-speed LAN types (Broadcast and Point-to-Point) use 10s Hello / 40s Dead timers. Slow WAN types (Point-to-Multipoint and NBMA) use 30s Hello / 120s Dead timers.
OSPF timer defaults are calibrated based on expected media speed and reliability.

Anahtar Kavram

OSPFv2 Network Types, DR/BDR Election Requirements, and Timer Defaults
Tahmini Süre:2m 0s
Soru 324Soru →

A network administrator is evaluating OSPFv2 operations across different interface types on Cisco routers. Which two statements accurately describe the characteristics and behavior of the OSPFv2 point-to-point network type compared to the broadcast multiaccess network type? (Choose two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: OSPFv2 suppresses the election of a Designated Router (DR) and Backup Designated Router (BDR) on point-to-point interfaces.; Point-to-point interfaces use default Hello and Dead timers of 10 seconds and 40 seconds, matching default broadcast network timers.

Cevap

The two correct statements are that OSPFv2 does not elect a DR/BDR on point-to-point network types, and point-to-point network types use default Hello and Dead timers of 10 seconds and 40 seconds.
The statements confirming that OSPFv2 suppresses DR/BDR elections on point-to-point interfaces and that point-to-point interfaces use 10-second Hello / 40-second Dead timers are correct. On point-to-point links, only two routers exist, so full mesh adjacency overhead is not an issue, rendering DR/BDR roles redundant. Furthermore, standard Ethernet point-to-point links default to 10s/40s timers identical to broadcast multiaccess links.

Adım Adım Çözüm

1
Analyze DR/BDR election requirements across OSPF network types.
Broadcast multiaccess networks elect a DR and BDR to reduce adjacency overhead on shared segments. Point-to-point links connect exactly two devices, making DR/BDR elections unnecessary.
Recognizing that point-to-point interface mode bypasses DR/BDR selection is fundamental to OSPF network design.
2
Verify default timer values for OSPFv2 network types.
Both broadcast and point-to-point network types default to a Hello timer of 10 seconds and a Dead timer of 40 seconds (4 times the Hello interval).
Timer consistency across matching network types ensures neighbors form adjacencies without timer mismatches.

Anahtar Kavram

OSPFv2 Point-to-Point vs Broadcast Network Type Characteristics
Soru 325Soru →

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

text
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

O 192.168.10.0/24 [110/20] via 10.1.1.1, 00:05:12, GigabitEthernet0/0
D 192.168.10.32/28 [90/307200] via 10.2.2.2, 00:12:44, GigabitEthernet0/1
S 192.168.10.32/27 [1/0] via 10.3.3.3, 01:00:15, GigabitEthernet0/2
S* 0.0.0.0/0 [1/0] via 10.0.0.1, 02:15:00, GigabitEthernet0/3

Which next-hop IP address will the router select to forward a packet addressed to 192.168.10.38?

Cevabı ve açıklamayı göster

Cevap: 10.2.2.2

Cevap

10.2.2.2
When an IP packet arrives, the router compares the destination address against all routing table entries. The route with the longest matching prefix (most specific subnet mask) is selected. Here, 192.168.10.32/28 has a prefix length of 28 bits, which is longer than /27, /24, or /0. Therefore, the router forwards the packet to 10.2.2.2.

Adım Adım Çözüm

1
Identify all candidate routes that encompass the target IP address 192.168.10.38
Candidate routes are 192.168.10.0/24 (range .0 - .255), 192.168.10.32/27 (range .32 - .63), 192.168.10.32/28 (range .32 - .47), and 0.0.0.0/0.
Routing decisions are evaluated by first determining which entries contain the destination host IP.
2
Apply the Longest Prefix Match (LPM) rule among valid candidate routes
192.168.10.32/28 has the longest subnet mask length (/28 > /27 > /24 > /0).
Routers always prefer the most specific route (longest prefix length) regardless of protocol or administrative distance.
3
Determine the next-hop IP associated with the winning prefix
The entry 192.168.10.32/28 forwards via next-hop IP 10.2.2.2.
The matching routing table entry explicitly specifies 10.2.2.2 as its next-hop.

Anahtar Kavram

Longest Prefix Match (LPM)
Tahmini Süre:1m 30s
Soru 326Soru →

A network administrator needs to manually configure an IPv4 static route to the destination subnet 192.168.10.0/24192.168.10.0/24 using the next-hop IP address 10.1.1.210.1.1.2 on a Cisco IOS router, starting from user EXEC mode. Place the CLI commands and actions in the correct sequential order from first to last.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence starts with entering privileged EXEC mode (`enable`), moving into global configuration mode (`configure terminal`), applying the static route command (`ip route 192.168.10.0 255.255.255.0 10.1.1.2`), and finally verifying the routing table entry (`show ip route static`) in privileged EXEC mode.
In Cisco IOS, configuration follows a strict hierarchy. User EXEC mode (`Router>`) must first be elevated to Privileged EXEC mode (`Router#`) using `enable`. Next, Global Configuration mode (`Router(config)#`) is accessed with `configure terminal`. The static route `ip route 192.168.10.0 255.255.255.0 10.1.1.2` is then entered. Finally, returning to Privileged EXEC mode permits running `show ip route static` to verify that the route is installed in the routing table.

Adım Adım Çözüm

1
Elevate privileges from User EXEC mode to Privileged EXEC mode.
Prompt changes from `Router>` to `Router#` after running `enable`.
Configuration commands cannot be executed directly from User EXEC mode.
2
Navigate to Global Configuration mode.
Prompt changes to `Router(config)#` after running `configure terminal`.
Static route configuration via `ip route` is a global configuration parameter.
3
Configure the IPv4 static route.
The command `ip route 192.168.10.0 255.255.255.0 10.1.1.2` is committed to running-config.
Specifies destination network prefix, subnet mask, and next-hop IP address.
4
Exit configuration mode and verify the routing table.
The `show ip route static` command displays `S 192.168.10.0/24 [1/0] via 10.1.1.2`.
Confirms the static route is installed in the IPv4 routing table successfully.

Anahtar Kavram

Cisco IOS CLI hierarchy navigation and static route command syntax
Soru 327Soru →

Two Cisco routers, R1 and R2, are connected to a shared Ethernet switch on the 10.1.1.0/24 broadcast multiaccess network running OSPFv2 in Area 0. Router R1 initializes first with an OSPF interface priority of 1 and a Router ID of 1.1.1.1. Seeing no other routers during its Wait timer, R1 elects itself as the Designated Router (DR). Ten minutes later, Router R2 is booted on the segment with its connected interface configured with an OSPF priority of 100 and a Router ID of 2.2.2.2. Which OSPF role will R2 assume on this network segment once neighbor adjacency is fully established?

Cevabı ve açıklamayı göster

Cevap: Backup Designated Router (BDR), while R1 remains the Designated Router (DR)

Cevap

Router R2 will assume the Backup Designated Router (BDR) role, while Router R1 remains the Designated Router (DR).
In OSPFv2 broadcast multiaccess networks, DR/BDR elections are non-preemptive. Once a router establishes itself as the active Designated Router (DR), it retains that role even if another router with a higher interface priority or higher Router ID subsequently joins the segment. Because R1 was already serving as DR and no BDR was present, R2 is elected as the Backup Designated Router (BDR).

Adım Adım Çözüm

1
Analyze the state of the OSPF segment when R1 boots alone.
R1 boots first, waits for neighbor Hellos during the Wait timer, finds no other router, and elects itself as the active DR on the multiaccess Ethernet segment.
On a broadcast multiaccess network, if no DR is present and no other candidate responds, the first active router assumes the DR role.
2
Evaluate OSPF DR/BDR election behavior when R2 joins the network.
OSPF DR and BDR elections are non-preemptive. An active DR will not be unseated by a newly connected router, regardless of the new router's higher OSPF interface priority or Router ID.
Non-preemption prevents network instability and frequent SPF recalculations whenever routers reboot or join the segment.
3
Determine the specific role assigned to R2.
Because a DR already exists (R1) and no BDR is currently active, R2 fills the vacant BDR position.
R2 has an eligible priority (100>0100 > 0), making it eligible for the BDR role.

Anahtar Kavram

Non-preemptive nature of OSPFv2 DR/BDR elections on broadcast multiaccess networks
Tahmini Süre:1m 15s
Soru 328Soru →

A Cisco router receives an IPv4 packet destined for host 172.16.5.45172.16.5.45. The routing table contains a static route configured with a next-hop IP address: `ip route 172.16.5.0 255.255.255.0 10.0.0.2`. In what chronological order does the router execute the forwarding decision and recursive lookup process to transmit this packet? Place the steps in order from first to last.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct operational order begins with inspecting the packet header to extract the destination IPv4 address, followed by executing a longest prefix match in the routing table. Next, because the matching static route points to a next-hop IP rather than an exit interface, the router performs a recursive lookup to find the egress interface. Finally, the router resolves the next-hop MAC address via ARP, encapsulates the packet into a Layer 2 frame, and transmits it.
Packet processing follows a strict sequential pipeline in Cisco IOS: Layer 3 packet destination extraction → Longest Prefix Match routing table lookup → Recursive resolution of the next-hop IP address to an exit interface → ARP MAC address resolution and Layer 2 frame transmission.

Adım Adım Çözüm

1
Packet Ingress & Header Inspection
Destination IP address 172.16.5.45172.16.5.45 is extracted.
Routing decisions require identifying the target host IP in the IP packet header.
2
Primary Routing Table Lookup
The static route entry `172.16.5.0/24 via 10.0.0.2` is selected based on Longest Prefix Match.
Cisco IOS routes traffic using the most specific matching network mask in the routing table.
3
Recursive Next-Hop Lookup
The next-hop IP 10.0.0.210.0.0.2 is resolved to a directly connected network and outbound interface.
Static routes configured solely with a next-hop IP require an additional lookup step to identify which physical or logical interface sends the traffic.
4
Layer 2 Encapsulation & Transmission
ARP table yields the destination MAC address for 10.0.0.210.0.0.2, frame is rewritten and transmitted.
Multi-access interfaces (like Ethernet) need a specific destination Layer 2 MAC address to transmit the packet.

Anahtar Kavram

IPv4 Static Route Recursive Lookup & Packet Forwarding Logic
Soru 329Soru →

An active OSPFv2 Designated Router (DR) on a multiaccess Ethernet segment suddenly fails. Place the operational recovery events and DR/BDR re-election steps in the correct chronological order from first to last.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct order of events following an OSPF DR failure is: (1) Neighbor routers detect DR loss via Dead Timer expiration, (2) The current BDR immediately promotes to DR, (3) Eligible routers initiate an election for the open BDR post, (4) The candidate with the highest interface priority or Router ID is elected new BDR, and (5) DROTHER routers complete FULL adjacency with the DR and new BDR while remaining in 2-WAY state with peer DROTHERs.
When an active DR fails, OSPF routers must first detect the loss when the Dead Router Timer expires. Upon detection, the active BDR is immediately promoted to DR without holding a new DR election. With the BDR position now vacant, remaining eligible routers (having priority > 0) participate in a BDR election, where the router with the highest interface priority (or highest Router ID if priorities are equal) wins. Finally, DROTHER routers form FULL adjacencies with both the DR and new BDR while maintaining 2-WAY state with non-DR/BDR peers.

Adım Adım Çözüm

1
Detect DR failure
Neighbors observe Dead Router Timer expiration.
OSPF routers on multiaccess networks wait until the Dead Timer expires without receiving Hello packets from the DR before taking action.
2
Promote active BDR
The existing BDR assumes the DR role.
OSPF avoids holding a fresh DR election; the pre-elected BDR instantly fills the DR position to ensure fast network convergence.
3
Trigger new BDR election
Eligible routers (priority > 0) initiate an election for the vacant BDR role.
Because the previous BDR was promoted to DR, the BDR position is empty and must be filled by a new election.
4
Determine election winner
The candidate with the highest interface priority (or highest Router ID) becomes the new BDR.
OSPF tie-breaking rules evaluate highest interface priority first, followed by highest Router ID.
5
Establish neighbor adjacencies
DROTHER routers transition to FULL state with the DR and new BDR while maintaining 2-WAY state with each other.
Multiaccess network design requires routers to form full adjacencies only with the DR and BDR to restrict link-state advertisement overhead.

Anahtar Kavram

OSPFv2 DR/BDR Non-Preemption and Failure Recovery Sequence
Tahmini Süre:2m 0s
Soru 330Soru →

An enterprise network features five routers participating in OSPFv2 on a shared Ethernet segment (192.168.12.0/24). A network engineer issues the command `show ip ospf neighbor` on router R3 and observes the following status output:

text
Neighbor ID Pri State Dead Time Address Interface
10.10.10.1 100 FULL/DR 00:00:35 192.168.12.1 GigabitEthernet0/0
10.10.10.2 50 FULL/BDR 00:00:38 192.168.12.2 GigabitEthernet0/0
10.10.10.4 0 FULL/DROTHER 00:00:31 192.168.12.4 GigabitEthernet0/0
10.10.10.5 200 FULL/DROTHER 00:00:36 192.168.12.5 GigabitEthernet0/0

If router 10.10.10.1 unexpectedly suffers an interface failure on GigabitEthernet0/0, which state transition will immediately occur on the segment?

Cevabı ve açıklamayı göster

Cevap: Router 10.10.10.2 is promoted to Designated Router (DR), and Router 10.10.10.5 is elected as the new Backup Designated Router (BDR).

Cevap

Router 10.10.10.2 is promoted to Designated Router (DR), and Router 10.10.10.5 is elected as the new Backup Designated Router (BDR).
In OSPF multiaccess networks, DR/BDR election follow two strict rules during failures: (1) When the DR goes down, the active BDR immediately assumes the DR role to maintain stability and prevent network re-convergence delays. (2) An election is subsequently conducted to fill the vacant BDR position. Since router 10.10.10.2 was the BDR, it becomes the DR. Among the remaining routers, router 10.10.10.5 has an interface priority of 200 (higher than remaining eligible routers), while router 10.10.10.4 has a priority of 0 (ineligible). Thus, router 10.10.10.5 is elected as the new BDR.

Adım Adım Çözüm

1
Analyze DR/BDR state transition upon DR failure
Router 10.10.10.2 (the current BDR) is automatically promoted to the Designated Router (DR) position.
OSPF DR/BDR election mechanics specify that whenever the current DR fails, the existing BDR takes over the DR role immediately without triggering a full DR election.
2
Evaluate eligibility for the newly vacant BDR position
Routers 10.10.10.4 (Priority 0) and 10.10.10.5 (Priority 200), alongside R3, are remaining neighbors.
Router 10.10.10.4 is configured with an interface priority of 0 (`ip ospf priority 0`), making it ineligible to become DR or BDR.
3
Determine the winner of the new BDR election
Router 10.10.10.5 wins the election and becomes the new BDR.
Among all eligible candidate routers for the vacant BDR role, Router 10.10.10.5 has the highest interface priority (200).

Anahtar Kavram

OSPFv2 DR/BDR Election Mechanics, Non-preemption, and Priority 0 Ineligibility
Soru 331Soru →

A network administrator needs to create a static route on router R1 to reach remote subnet 2001:db8:100:50::/642001:\text{db8}:100:50::/64. The administrator decides to specify the next-hop router R2 using R2's link-local address fe80::20c:29ff:fe01:a1b2fe80::20c:29ff:fe01:a1b2 across R1's outbound GigabitEthernet 0/0/1 interface. Which Cisco IOS command correctly configures this IPv6 static route?

Cevabı ve açıklamayı göster

Cevap: ipv6 route 2001:db8:100:50::/64 GigabitEthernet0/0/1 fe80::20c:29ff:fe01:a1b2

Cevap

The command 'ipv6 route 2001:db8:100:50::/64 GigabitEthernet0/0/1 fe80::20c:29ff:fe01:a1b2' correctly configures the fully specified IPv6 static route.
The correct command uses the 'ipv6 route' keyword followed by the target destination network prefix (2001:db8:100:50::/642001:\text{db8}:100:50::/64), the local egress interface (GigabitEthernet0/0/1), and the link-local address of the adjacent router (fe80::20c:29ff:fe01:a1b2fe80::20c:29ff:fe01:a1b2). Because link-local addresses are valid only on their local segment, including the local exit interface is mandatory.

Adım Adım Çözüm

1
Identify the proper command prefix for IPv6 static routing.
The command must begin with 'ipv6 route'.
Cisco IOS separates IPv4 ('ip route') and IPv6 ('ipv6 route') static configuration commands.
2
Evaluate next-hop requirements when using link-local addresses.
Both the exit interface and the link-local next-hop IPv6 address must be specified.
Link-local addresses (fe80::/10) are local to a specific link. Without specifying the exit interface, the router cannot determine which physical segment the link-local address belongs to.
3
Verify command syntax order.
Syntax: 'ipv6 route <destination-prefix/prefix-length> <exit-interface> <link-local-address>'.
This fully specified static route syntax satisfies all Cisco IOS requirements for link-local next-hops.

Anahtar Kavram

IPv6 Fully Specified Static Routing with Link-Local Next-Hop
Soru 332Soru →

In an enterprise WAN edge topology, router HQ-GW receives a path to subnet 10.80.0.0/1410.80.0.0/14 via a redistributed routing process resulting in an EIGRP External route (default Administrative Distance of 170170). An administrator needs to configure a floating static backup route for destination subnet 10.80.0.0/1410.80.0.0/14 using next-hop IP 192.168.200.1192.168.200.1 over an auxiliary link.

What minimum Administrative Distance integer value must be appended to the Cisco IOS command so that the static route remains dormant until the primary EIGRP External route fails?

Aşağıdaki boşlukları doldurun

ip route 10.80.0.0 255.240.0.0 192.168.200.1
Cevabı ve açıklamayı göster

Cevap

171
Cisco IOS routes are populated into the routing table based on Administrative Distance (AD), where lower values indicate higher trustworthiness. EIGRP External routes possess a default AD of 170. For a static route to act as a floating backup (remaining inactive until the primary path fails), its AD must be set higher than the primary path's AD. The minimum integer value greater than 170 is 171.

Adım Adım Çözüm

1
Identify the Administrative Distance (AD) of the primary routing source.
EIGRP External routes have a standard Cisco IOS default AD of 170.
Routing decisions in Cisco IOS select the path with the lowest Administrative Distance.
2
Determine the required Administrative Distance condition for a floating static route.
The floating static route's AD must be strictly greater than 170.
If the static route's AD were less than or equal to 170, it would either override the primary path or cause equal-cost multi-pathing/route instability rather than serving strictly as a backup.
3
Calculate the minimum integer AD required for the static route command.
170 + 1 = 171.
171 is the lowest whole integer value greater than the primary path's AD of 170.

Anahtar Kavram

Floating Static Route Administrative Distance Selection
Soru 333Soru →

An enterprise Cisco router receives an IPv4 packet destined for IP address 192.168.50.75. The router's routing table contains the following entries:

text
Codes: C - connected, S - static, O - OSPF, D - EIGRP

Gateway of last resort is not set

192.168.50.0/24 is variably subnetted, 4 subnets, 3 masks
O 192.168.50.0/24 [110/20] via 10.1.1.1, 00:14:22, GigabitEthernet0/0
S 192.168.50.0/25 [1/0] via 10.3.3.3
D 192.168.50.64/26 [90/30720] via 10.2.2.2, 00:08:15, GigabitEthernet0/1
C 192.168.50.64/28 is directly connected, GigabitEthernet0/2

Which forwarding path will the router select to forward this packet?

Cevabı ve açıklamayı göster

Cevap: Out GigabitEthernet0/2, because 192.168.50.64/28 provides the longest matching prefix for the destination IP address.

Cevap

The router will forward the packet out interface GigabitEthernet0/2 because the directly connected prefix 192.168.50.64/28 provides the longest prefix match (28 matching bits) for the destination IP 192.168.50.75.
When a router makes a packet forwarding decision, it checks all routes in the IPv4 routing table that encompass the destination IP address. The fundamental rule of IP routing is Longest Prefix Match (LPM): the route with the most specific prefix length (largest prefix number) is selected. Here, the target IP 192.168.50.75 falls into 192.168.50.64/28 (range .64 to .79). Because /28 is longer than /26, /25, and /24, the router forwards the packet directly out GigabitEthernet0/2.

Adım Adım Çözüm

1
Determine subnet ranges for all routing table entries
192.168.50.0/24 covers 192.168.50.0–192.168.50.255; 192.168.50.0/25 covers 192.168.50.0–192.168.50.127; 192.168.50.64/26 covers 192.168.50.64–192.168.50.127; 192.168.50.64/28 covers 192.168.50.64–192.168.50.79.
Identify which routes in the routing table actually match the destination IP address 192.168.50.75.
2
Check destination IP 192.168.50.75 against matching subnets
The destination address 192.168.50.75 matches all four listed routes in the routing table.
All four routes enclose the IP address 192.168.50.75 within their network address boundaries.
3
Apply the Longest Prefix Match (LPM) rule
Prefix lengths are /24, /25, /26, and /28. The /28 prefix has the greatest number of matching subnet mask bits.
Cisco IOS routing logic prioritizes the most specific prefix (longest netmask / highest prefix length) first before evaluating Administrative Distance or Metric.

Anahtar Kavram

Longest Prefix Match (LPM) Rule in Cisco IPv4 Routing
Soru 334Soru →

An enterprise router with default settings maintains the following simplified IPv4 routing table excerpt:

text
Codes: C - connected, S - static, O - OSPF

O 10.12.0.0/16 [110/20] via 172.16.1.1, 00:15:30, GigabitEthernet0/0
S 10.12.32.0/20 [1/0] via 172.16.2.1, GigabitEthernet0/1
O 10.12.32.0/24 [110/50] via 172.16.3.1, 00:08:12, GigabitEthernet0/2
S 10.12.32.16/28 [200/0] via 172.16.4.1, GigabitEthernet0/3

The router receives an IP packet addressed to destination 10.12.32.2210.12.32.22. Which two statements correctly describe how the router processes and forwards this packet?

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: The router forwards the packet out GigabitEthernet0/3 toward next-hop 172.16.4.1 because the /28 route provides the longest prefix match.; The router evaluates prefix length before administrative distance, ignoring lower administrative distance values on broader subnets.

Cevap

The router forwards the packet out GigabitEthernet0/3 toward 172.16.4.1 using the longest prefix match (/28), and ignores lower administrative distance routes because prefix length comparison takes precedence over administrative distance.
When a router receives a packet, it searches its routing table for all matching prefixes and selects the route with the longest prefix match (most specific subnet mask). The destination address 10.12.32.22 matches four entries, but 10.12.32.16/28 has the longest prefix length (/28). Thus, the router forwards the packet via GigabitEthernet0/3. Administrative Distance is ignored when comparing different prefix lengths.

Adım Adım Çözüm

1
Determine which routing table entries match the destination IP address 10.12.32.22.
The destination address matches four routes: 10.12.0.0/16, 10.12.32.0/20, 10.12.32.0/24, and 10.12.32.16/28 (host range 10.12.32.17 - 10.12.32.30).
All four network blocks encompass the destination IP 10.12.32.22.
2
Apply the Longest Prefix Match (LPM) rule.
The /28 prefix length is the longest (most specific) match among /16, /20, /24, and /28.
The router forwarding decision logic strictly prioritizes the route with the most matching network bits (longest subnet mask).
3
Evaluate the impact of Administrative Distance and Metric.
Administrative Distance (200 vs 1 vs 110) is not compared across different prefix lengths; the /28 route is selected regardless of AD.
Administrative Distance is only used to select between multiple routes to the exact same prefix length.

Anahtar Kavram

Router Forwarding Decision Logic (Longest Prefix Match)
Soru 335Soru →

Match each Cisco IPv4 routing table component to its correct functional description based on standard Cisco IOS routing operations.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Destination Prefix and Subnet Mask
Administrative Distance
Routing Metric
Next-Hop IP Address

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

Destination Prefix and Subnet Mask matches 'Specifies the target network address range evaluated using longest prefix match logic.' Administrative Distance matches 'Defines the believability or trustworthiness rating of a route source when multiple protocols learn the same destination.' Routing Metric matches 'Represents the path cost or tie-breaker value calculated by a specific routing protocol to select the best path.' Next-Hop IP Address matches 'Indicates the IP address of the adjacent router interface to which traffic for the network should be forwarded.'
Each routing table component serves a distinct role in Cisco packet forwarding. The destination prefix identifies the destination subnet; administrative distance evaluates source trustworthiness across protocols; the metric determines path cost within the same protocol; and the next-hop address identifies the adjacent forwarding device.

Adım Adım Çözüm

1
Analyze the role of Destination Prefix and Subnet Mask
Identifies the network boundary used during prefix matching.
The subnet mask specifies how many bits represent the network portion of an IP address.
2
Analyze Administrative Distance (AD)
Identifies the administrative ranking between different protocol sources (e.g., OSPF AD 110 vs. EIGRP AD 90).
AD measures route source trustworthiness before routes enter the routing table.
3
Analyze Routing Metric
Identifies protocol-specific path evaluation metrics (e.g., bandwidth, delay, cost).
Metrics compare alternative paths provided by the same routing protocol.
4
Analyze Next-Hop IP Address
Identifies the adjacent forwarding device address.
Routers rewrite Layer 2 headers using the MAC address corresponding to the next-hop IP.

Anahtar Kavram

Routing Table Components and Interpretation
Soru 336Soru →

Match each OSPFv2 network configuration or interface state on the left with its correct DR/BDR election behavior and timer trait on the right.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Öğeler

Broadcast Network Type
Point-to-Point Network Type
Interface OSPF Priority set to 0

Eşleşmeler

Cevabı ve açıklamayı göster

Cevap

Broadcast Network Type pairs with electing a DR/BDR using 10s/40s timers; Point-to-Point Network Type pairs with forming direct adjacencies without DR/BDR election using 10s/40s timers; Interface OSPF Priority set to 0 pairs with rendering the router interface completely ineligible for DR/BDR election.
Each OSPF network type has specific rules regarding DR/BDR elections and default timers. Broadcast networks elect DR/BDRs and use 10s/40s timers. Point-to-Point networks bypass DR/BDR elections entirely while sharing the 10s/40s timer defaults. Setting interface priority to 0 explicitly revokes DR/BDR eligibility.

Adım Adım Çözüm

1
Analyze OSPF Broadcast media characteristics.
Broadcast networks (like Ethernet) require DR and BDR election to reduce adjacencies on multiaccess segments, operating with 10s Hello and 40s Dead timers.
Broadcast multiaccess segments require a central Designated Router to handle LSA flooding.
2
Evaluate Point-to-Point OSPF network behavior.
Point-to-point links only connect two devices, so no DR/BDR election is needed, though 10s Hello and 40s Dead timers are still used.
DR/BDR election is unnecessary when only two routers share the link.
3
Determine the impact of setting OSPF interface priority to 0.
Setting the priority to 0 disqualifies the router interface from becoming DR or BDR.
Cisco IOS uses priority 0 specifically to keep lower-capacity routers in DROTHER state.

Anahtar Kavram

OSPFv2 Network Types and DR/BDR Selection Criteria
Soru 337Soru →

A network administrator is configuring IPv4 static routes on a Cisco router to connect a branch site. Which two statements accurately describe the operational characteristics of static routing syntax and forwarding decisions on Cisco routers? (Select two.)

Geçerli olan tümünü seçin

Cevabı ve açıklamayı göster

Cevap: Specifying a next-hop IPv4 address requires the router to perform a recursive lookup to determine the egress interface.; Specifying an exit interface directly on a point-to-point link allows the router to forward traffic without a recursive lookup.

Cevap

The statement explaining that specifying a next-hop IPv4 address requires a recursive lookup, and the statement explaining that specifying an exit interface on a point-to-point link avoids a recursive lookup.
The correct statements reflect standard Cisco IOS forwarding logic: specifying a next-hop IP address forces a recursive routing table lookup to identify the egress interface, whereas specifying a directly connected exit interface on a point-to-point link allows immediate interface mapping without recursive lookup.

Adım Adım Çözüm

1
Analyze static route next-hop lookup behavior.
When a static route uses a next-hop IPv4 address, the router must search its routing table a second time (recursive lookup) to find which outgoing interface reaches that next-hop address.
Next-hop resolution determines physical layer 2 and egress interface mapping.
2
Analyze static route exit interface lookup behavior on point-to-point links.
When an exit interface is specified directly on a point-to-point connection, the router immediately knows which physical interface to forward the packet out of.
Directly connected point-to-point links do not require recursive next-hop IP resolution.

Anahtar Kavram

IPv4 Static Route Forwarding & Syntax Characteristics
Tahmini Süre:1m 0s
Soru 338Soru →

Four Cisco routers (HQ-R1, HQ-R2, HQ-R3, and HQ-R4) are connected to a shared GigabitEthernet switch on the broadcast multiaccess network 10.200.1.0/2410.200.1.0/24. All routers are powered on simultaneously with default OSPFv2 settings except for interface priority values. The interfaces are configured as follows:

- HQ-R1: `ip ospf priority 0`, Loopback0: 192.168.100.1/32192.168.100.1/32, Gi0/0: 10.200.1.1/2410.200.1.1/24
- HQ-R2: `ip ospf priority 10`, Loopback0: 10.10.10.10/3210.10.10.10/32, Gi0/0: 10.200.1.2/2410.200.1.2/24
- HQ-R3: `ip ospf priority 20`, Loopback0: 1.1.1.1/321.1.1.1/32, Gi0/0: 10.200.1.3/2410.200.1.3/24
- HQ-R4: `ip ospf priority 20`, Loopback0: 2.2.2.2/322.2.2.2/32, Gi0/0: 10.200.1.4/2410.200.1.4/24

Which router role assignment correctly describes the outcome of the DR/BDR election on this Ethernet segment?

Cevabı ve açıklamayı göster

Cevap: HQ-R4 is elected as DR, and HQ-R3 is elected as BDR.

Cevap

HQ-R4 is elected as DR, and HQ-R3 is elected as BDR.
In OSPF DR/BDR elections on broadcast multiaccess networks, routers first evaluate interface priority values. An interface priority of 0 immediately excludes a router (HQ-R1) from election eligibility. Between HQ-R3 and HQ-R4, both share the highest priority (20). The tie is broken by comparing their Router IDs (derived from active loopback interfaces). Because 2.2.2.22.2.2.2 is greater than 1.1.1.11.1.1.1, HQ-R4 wins the DR election, and HQ-R3 becomes the BDR.

Adım Adım Çözüm

1
Evaluate interface priority eligibility
HQ-R1 has an OSPF priority of 0 and is immediately excluded from becoming DR or BDR, despite having the highest loopback IP address (192.168.100.1192.168.100.1).
An OSPF priority of 0 explicitly configured on an interface renders the router ineligible for DR/BDR election.
2
Compare interface priorities among remaining routers
HQ-R3 and HQ-R4 both have an interface priority of 20, which is strictly higher than HQ-R2's priority of 10.
OSPF DR/BDR election primary criterion is highest interface priority.
3
Break priority tie using Router ID
HQ-R3 has Router ID 1.1.1.11.1.1.1 (from Loopback0) and HQ-R4 has Router ID 2.2.2.22.2.2.2 (from Loopback0). Since 2.2.2.2>1.1.1.12.2.2.2 > 1.1.1.1, HQ-R4 is elected DR, and HQ-R3 is elected BDR.
When interface priorities tie, the highest OSPF Router ID breaks the tie.

Anahtar Kavram

OSPFv2 DR/BDR election precedence (Priority > Router ID) and Priority 0 exclusion
Tahmini Süre:2m 0s
Soru 339Soru →

A network administrator configures the interface command `ip ospf priority 0` on a router's GigabitEthernet interface connected to a broadcast multiaccess Ethernet network. What is the effect of setting the OSPF priority to 0 on this interface?

Cevabı ve açıklamayı göster

Cevap: The router becomes completely ineligible to be elected as a Designated Router (DR) or Backup Designated Router (BDR).

Cevap

The router becomes completely ineligible to be elected as a Designated Router (DR) or Backup Designated Router (BDR).
In OSPFv2 broadcast networks, setting the interface priority to 0 explicitly disables the router from participating in Designated Router (DR) or Backup Designated Router (BDR) elections. The router will remain in the DROTHER state for that segment regardless of its Router ID or IP addresses.

Adım Adım Çözüm

1
Identify the function of OSPF interface priority on multiaccess networks.
Interface priority (default value of 1) determines candidate preference during DR and BDR elections.
OSPF uses priority values ranging from 0 to 255 to control router roles on broadcast segments.
2
Evaluate the special meaning of priority value 0.
A priority setting of 0 forces the interface into a DROTHER state, preventing it from ever becoming a DR or BDR.
By OSPF design, priority 0 indicates non-participation in election roles.

Anahtar Kavram

OSPF Priority 0 DR/BDR Election Exclusion
Tahmini Süre:45s
Soru 340Soru →

Four Cisco routers (R1, R2, R3, and R4) are booted simultaneously on a shared broadcast multiaccess Ethernet segment running OSPFv2 in Area 0. No explicit OSPF router ID is configured under the `router ospf` process on any router.

The interface and active IP configurations are as follows:
- R1: GigabitEthernet0/0 IP 192.168.1.1/24192.168.1.1/24, Priority = 1010; Loopback0 IP = 10.1.1.1/3210.1.1.1/32
- R2: GigabitEthernet0/0 IP 192.168.1.2/24192.168.1.2/24, Priority = 00; Loopback0 IP = 172.16.1.1/32172.16.1.1/32
- R3: GigabitEthernet0/0 IP 192.168.1.3/24192.168.1.3/24, Priority = 1010; Loopback0 IP = 10.2.2.2/3210.2.2.2/32
- R4: GigabitEthernet0/0 IP 192.168.1.4/24192.168.1.4/24, Priority = 2020; Loopback0 IP = 10.0.0.1/3210.0.0.1/32

Order the routers in sequence from highest to lowest precedence during the initial Designated Router (DR) and Backup Designated Router (BDR) election, starting with the router selected as DR down to the completely ineligible router.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence from highest election precedence to lowest is: Router R4 (DR), Router R3 (BDR), Router R1 (DROTHER), and Router R2 (Ineligible).
The election evaluates interface priority first. Router R4 has the highest interface priority (20) and is elected DR. Router R2 has a priority of 0, making it strictly ineligible for DR/BDR election despite having the highest Loopback IP address. Between Router R1 and Router R3 (both having priority 10), Router R3 wins the BDR election because its loopback address (10.2.2.2) forms a higher Router ID than Router R1 (10.1.1.1). Router R1 becomes a DROTHER.

Adım Adım Çözüm

1
Determine initial eligibility based on configured interface priority.
Router R2 has an OSPF interface priority of 0, which immediately disqualifies it from DR/BDR election eligibility, placing it at the bottom of the election ranking.
An OSPF interface priority of 0 specifies that the router cannot become a DR or BDR on the segment.
2
Evaluate eligible candidate routers by interface priority to select the DR.
Router R4 has a priority of 20, while Router R1 and Router R3 each have a priority of 10. Router R4 wins the DR election.
OSPF interface priority is the primary criteria for DR/BDR election; the router with the highest numeric priority value wins.
3
Break the priority tie between remaining eligible routers for BDR selection using Router ID.
Router R3 and Router R1 tie with an interface priority of 10. Router R3 has an active Loopback0 IP of 10.2.2.2, which becomes its Router ID. Router R1 has a Loopback0 IP of 10.1.1.1. Because 10.2.2.2 > 10.1.1.1, Router R3 is elected BDR and Router R1 becomes a DROTHER.
When interface priorities are equal, OSPF uses the highest Router ID (derived automatically from the highest active loopback IP address) as the secondary tie-breaker.

Anahtar Kavram

OSPFv2 DR/BDR Election Precedence (Interface Priority > Highest Router ID via Loopback > Priority 0 Ineligibility)
Tahmini Süre:2m 0s
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