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IP Connectivity

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Question 441Question →

A network administrator has configured HSRPv2 between two routers, R1 (Active, priority 110, interface tracking decrements priority by 30) and R2 (Standby, priority 100, preemption enabled). Arrange the operational steps in the correct chronological sequence from the moment R1's tracked interface fails until R2 successfully handles traffic as the new Active router.

Drag items to arrange them in the correct order

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Answer

The correct chronological order is: 1) R1 detects tracked interface failure and reduces priority to 80; 2) R1 advertises the degraded priority via HSRP Hello; 3) R2 identifies its higher priority and sends an HSRP Coup message; 4) R1 relinquishes active status and broadcasts an HSRP Resign message; 5) R2 assumes the Active state and broadcasts a Gratuitous ARP to update switch CAM tables.
The failover process begins locally on R1 when the tracked link drops, causing priority degradation. Next, R1 informs the segment via Hello packets containing the updated priority. R2 evaluates this priority against its own higher priority and uses its preemption configuration to send a Coup message. R1 acknowledges this by relinquishing control and issuing a Resign message while moving to Standby state. Finally, R2 assumes the Active state and broadcasts a Gratuitous ARP to rewrite switch port bindings for the shared virtual MAC address.

Step-by-Step Solution

1
Identify the initial triggering event
R1's tracked interface drops, reducing R1's priority from 110 to 80.
HSRP interface tracking dynamically recalculates priority immediately upon physical link or line protocol failure.
2
Determine how priority changes are communicated
R1 transmits Hello packets advertising priority 80.
HSRP routers exchange control messages periodically to communicate current group state and priority values.
3
Analyze preemption logic on the standby device
R2 observes R1's priority (80) is lower than R2's (100) and sends a Coup packet.
Preemption allows a router with higher priority than the current Active router to claim the Active role.
4
Trace active router role surrender
R1 transitions to Standby after issuing a Resign packet.
Receiving a valid Coup from a higher-priority router forces the current Active router to yield leadership.
5
Verify Layer 2 forwarding convergence
R2 moves to Active state and emits a Gratuitous ARP.
GARP ensures attached Layer 2 switches immediately rewrite their MAC tables so traffic sent to the virtual IP/MAC reaches R2.

Key Concept

HSRP Preemption and Interface Tracking Convergence Sequence
Question 442Question →

A network engineer initializes OSPFv2 on a Cisco router using the configuration below:

router ospf 10
router-id 1.1.1.1
network 10.1.1.0 0.0.0.3 area 0

The router also has an active Loopback 0 interface with IP address 172.16.1.1/24 and an active GigabitEthernet0/0 interface with IP address 10.1.1.1/30.

After neighbor adjacencies are established, the engineer enters OSPF configuration mode and executes the command `router-id 2.2.2.2`. No further commands are issued, and the router is not rebooted.

Which IP address is currently used as the active OSPF Router ID by the running OSPF process?

Show answer & explanation

Answer: 1.1.1.1

Answer

1.1.1.1 is the active OSPF Router ID because changing the router-id configuration does not update the operational Router ID until the OSPF process is cleared or the router is restarted.
The correct choice is 1.1.1.1. When OSPF initializes, the explicit `router-id` command overrides all interface IP addresses. Once selected and active, changing the `router-id` setting does not dynamically change the operational router ID until the OSPF process is restarted using the `clear ip ospf process` privileged EXEC mode command or by reloading the device.

Step-by-Step Solution

1
Determine initial Router ID election
The OSPF process elected 1.1.1.1 because an explicit `router-id` command takes highest precedence during initialization.
Explicit configuration overrides loopback and physical interface IP addresses.
2
Analyze the impact of changing the `router-id` command on an active process
Configuring `router-id 2.2.2.2` updates the running configuration file, but does NOT dynamically reset active neighbor adjacencies or change the live operational Router ID.
OSPF requires an explicit process reset via `clear ip ospf process` or a device reboot to enact a new Router ID.
3
Identify the current operational Router ID
The operational Router ID remains 1.1.1.1.
No process restart command was executed after changing the configuration.

Key Concept

OSPFv2 Router ID Non-Preemptive Precedence and Process Reset Requirement
Question 443Question →

A network engineer needs to configure a floating static route on Cisco router R1 for destination subnet 10.10.20.0/2410.10.20.0/24 via next-hop IP 192.168.1.2192.168.1.2. The route must serve as a backup to an existing OSPF path, which has a default Administrative Distance of 110110. The engineer decides to set the backup route's Administrative Distance to 130130.

Complete the Cisco IOS global configuration command below by filling in the missing trailing Administrative Distance value.

Fill in the blanks below

R1(config)# ip route 10.10.20.0 255.255.255.0 192.168.1.2
Show answer & explanation

Answer

The trailing Administrative Distance value required to complete the command is 130.
Specifying 130 at the end of the `ip route` command assigns an Administrative Distance higher than the primary OSPF route's AD of 110. This keeps the route out of the routing table during normal operation and activates it only when the primary path is removed.

Step-by-Step Solution

1
Identify the standard Cisco IOS syntax for a static route.
The basic command syntax is `ip route <prefix> <mask> <next-hop> [distance]`.
Placing an optional integer value at the end of the static route command assigns a custom Administrative Distance.
2
Determine the requested Administrative Distance value for the floating static route.
The specified Administrative Distance value is 130.
Setting the AD to 130 ensures it is higher than OSPF's default AD of 110, keeping the static route floating in reserve until the OSPF route fails.

Key Concept

Floating Static Route CLI Syntax and Administrative Distance
Estimated Time:1m 0s
Question 444Question →

Match each element of a Cisco IPv4 routing table entry on the left with its corresponding operational role on the right.

Click a left item, then click its matching right item

Items

First integer inside brackets (e.g., 110 in [110/65])
Second integer inside brackets (e.g., 65 in [110/65])
IP address following 'via' (e.g., 10.1.1.2)
Interface designation at the end of entry (e.g., GigabitEthernet0/0/1)

Matches

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Answer

The first integer inside the brackets matches the Administrative Distance (trustworthiness of the route source). The second integer inside the brackets matches the Metric (routing protocol path cost). The IP address following 'via' matches the next-hop address. The interface designation matches the local egress interface.
In Cisco IOS routing table output entries (such as O 192.168.10.0/24 [110/65] via 10.1.1.2, GigabitEthernet0/0/1), the components strictly follow a defined syntax: the first bracketed integer is the Administrative Distance (believability/trustworthiness rating), the second bracketed integer is the routing protocol metric (cost of the path), the IP address following 'via' is the next-hop address of the adjacent router, and the ending interface identifier is the local exit port.

Step-by-Step Solution

1
Analyze the Cisco routing table entry bracket notation [AD/Metric].
Identify that the first number represents Administrative Distance and the second number represents Metric cost.
Cisco IOS routes display bracketed values formatted strictly as [Administrative Distance / Metric].
2
Examine the forwarding path descriptors ('via IP' and interface name).
Map 'via IP' to the next-hop router's address and the interface name to the local outbound port.
'via' indicates the immediate upstream router address, while the final parameter indicates the local exit interface.

Key Concept

Routing Table Components & Cisco IOS Route Entry Structure
Question 445Question →

Which two statements accurately describe the default operational characteristics of Cisco Hot Standby Router Protocol version 1 (HSRPv1)? (Select two.)

Select all that apply

Show answer & explanation

Answer: Preemption is disabled by default on HSRP-enabled interfaces.; The default interface priority assigned to an HSRP group member is 100.

Answer

Preemption is disabled by default on HSRP-enabled interfaces, and the default interface priority assigned to an HSRP group member is 100.
The correct options accurately identify default HSRP behavior: preemption is disabled by default so a higher-priority router does not automatically assume the active role, and the default interface priority value is 100.

Step-by-Step Solution

1
Evaluate default HSRP priority settings
Confirm that Cisco IOS assigns a default priority of 100 to HSRP group interfaces.
Priorities range from 0 to 255, with 100 being the baseline default.
2
Evaluate default HSRP preemption behavior
Confirm that preemption is disabled by default in HSRP.
Without the standby preempt command, a newly booted or recovered router with a higher priority remains in Standby state.
3
Verify virtual IP rules and tie-breaking logic
Identify incorrect statements regarding physical IP reuse and tie-breaker rules.
HSRP virtual IPs must not equal physical interface IPs, and tie-breakers favor the highest IP address.

Key Concept

HSRP Default Operational Parameters and Preemption Mechanics
Question 446Question →

A network operations engineer is migrating a dual-core distribution block from VRRPv2 to HSRPv2. During the migration on Switch-1 (interface VLAN 50, IPv4 address 10.50.1.1/24), the engineer attempts to assign 10.50.1.1 as the HSRP virtual IP address using the command `standby 50 ip 10.50.1.1`. The IOS XE CLI immediately returns an error and rejects the configuration. Which statement correctly explains the protocol design difference causing this failure?

Show answer & explanation

Answer: HSRP requires the virtual IP address to be an unassigned IP address within the subnet, whereas VRRP allows a router interface physical IP address to serve as the virtual IP address.

Answer

HSRP requires the virtual IP address to be an unassigned IP address within the subnet, whereas VRRP allows a router interface physical IP address to serve as the virtual IP address.
In HSRP, the virtual IP address must be a distinct, unassigned address within the IP subnet shared by the participating routers. VRRP supports IP address ownership (where the virtual IP matches a physical interface IP address and gives that router priority 255), but HSRP strictly disallows assigning a router's physical interface IP address as the HSRP virtual IP address.

Step-by-Step Solution

1
Analyze the operational rules for Cisco HSRP virtual IP address configuration.
HSRP (v1 and v2) mandates that the configured virtual IP address must be a unique, unassigned IP address within the local primary subnet and cannot match the physical IP address of any participating router interface.
Preventing IP overlap ensures standard ARP/ICMP processing and prevents local interface address conflicts in HSRP state machines.
2
Compare HSRP behavior with VRRP IP address ownership functionality.
VRRP permits the IP address owner scenario where the virtual IP matches the physical IP address of an interface on the Master router (setting priority automatically to 255).
This key design difference explains why a configuration valid in VRRP fails when replicated directly in HSRP.

Key Concept

First Hop Redundancy Protocols (HSRP vs. VRRP Virtual IP Assignment Rules)
Question 447Question →

Two Cisco routers are attempting to establish an OSPFv2 adjacency over a point-to-point link. During the neighbor formation process, the routers exchange empty Database Description (DBD) packets to negotiate the Master/Slave relationship and select the initial sequence number. In which specific OSPF neighbor state does this negotiation take place?

Show answer & explanation

Answer: ExStart; EXSTART; ExStart state; exstart

Answer

ExStart
In the ExStart state, neighbor routers use empty Database Description (DBD) packets to determine which router acts as the Master and which acts as the Slave, as well as set the initial DBD sequence number. The router with the higher Router ID wins the Master role.

Step-by-Step Solution

1
Identify the OSPF neighbor state where Master/Slave election occurs
The ExStart (Exchange Start) state is designated for establishing the Master/Slave relationship.
Before exchanging Link State Advertisements (LSAs), routers must determine which device controls the sequence numbering of DBD packets.
2
Verify the role of DBD packets in this state
In ExStart, empty DBD packets containing the MS (Master/Slave), Init, and More bits are exchanged along with Router IDs.
The router with the higher Router ID becomes the Master.

Key Concept

OSPF Neighbor States (ExStart)
Estimated Time:1m 0s
Question 448Question →

An enterprise router receives a primary path for the prefix 192.168.50.0/24192.168.50.0/24 via OSPF. An engineer attempts to configure a floating static backup route using the command `ip route 192.168.50.0 255.255.255.0 10.0.0.2 105`. However, after entering the command, the routing table immediately replaces the OSPF path with the static route. What is the cause of this behavior?

Show answer & explanation

Answer: The static route was assigned an administrative distance of 105, which is lower than the default OSPF administrative distance of 110.

Answer

The static route was assigned an administrative distance of 105, which is lower than the default OSPF administrative distance of 110.
Cisco IOS selects routes based on Administrative Distance (AD), where lower AD values indicate higher trustworthiness. Default OSPF has an AD of 110. Because the engineer configured the static route with an AD of 105, it is lower than OSPF's AD of 110. Consequently, the router prefers the static route and installs it into the routing table immediately, preventing it from functioning as a backup route. A proper floating static route for OSPF must be configured with an AD greater than 110 (such as 120).

Step-by-Step Solution

1
Identify the default Administrative Distance (AD) for the primary routing protocol (OSPF).
OSPF has a default AD of 110.
Cisco IOS uses AD values to determine route trustworthiness when multiple routing sources offer paths to the exact same destination.
2
Evaluate the AD assigned to the static route in the command `ip route 192.168.50.0 255.255.255.0 10.0.0.2 105`.
The trailing value 105 configures the static route AD to 105.
The optional numeric argument at the end of a static route statement specifies its administrative distance.
3
Compare the static route AD against the primary OSPF route AD.
Because 105<110105 < 110, the static route has a lower (more preferred) AD than OSPF.
Lower AD values take precedence in routing table installation. To act as a floating static backup, the static route AD must be configured with a value strictly greater than the primary protocol AD (e.g., AD > 110).

Key Concept

Floating Static Route Administrative Distance Requirements
Question 449Question →

A network administrator is connecting multiple routers to a shared multiaccess Ethernet segment running OSPFv2. Place the parameter criteria used to determine the Designated Router (DR) election winner in order of evaluation precedence, starting with the parameter evaluated first down to the final fallback tie-breaker.

Drag items to arrange them in the correct order

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Answer

The correct order of precedence for OSPFv2 DR election is: (1) Highest OSPF interface priority value, (2) 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 DR/BDR election process evaluates interface priority first, where the highest non-zero priority wins. If priorities are tied, OSPF breaks the tie using the Router ID. The Router ID selection itself follows a strict hierarchy: explicit configuration first, followed by the highest active loopback IP address, and finally the highest active physical interface IP address.

Step-by-Step Solution

1
Evaluate OSPF interface priority
Highest priority (1-255) wins. A priority of 0 excludes the router from becoming DR/BDR.
Interface priority is the primary metric defined by OSPF for DR/BDR election.
2
Evaluate explicit Router ID if priorities tie
Router with the highest router-id command value wins.
If interface priorities are equal, OSPF uses the Router ID as a tie-breaker, preferring manually defined IDs.
3
Evaluate loopback interfaces if no explicit Router ID exists
Router with the highest IP address on an active loopback interface wins.
Loopback interfaces provide stability and automatically take precedence over physical interfaces for Router ID selection.
4
Evaluate physical interfaces if no loopback or explicit Router ID exists
Router with the highest IP address on an active physical interface wins.
Physical interface IP addresses serve as the absolute fallback for Router ID determination.

Key Concept

OSPFv2 DR/BDR Election Precedence Criteria
Question 450Question →

A Cisco router receives an IPv4 packet destined for host 192.168.4.66. The routing table contains the following entries:

text
Gateway of last resort is not set

192.168.4.0/24 is variably subnetted, 4 subnets, 4 masks
S 192.168.4.0/24 [1/0] via 172.16.4.4
B 192.168.4.64/26 [20/0] via 172.16.3.3, 01:45:10, GigabitEthernet0/2
D 192.168.4.64/27 [90/307200] via 172.16.2.2, 00:15:30, GigabitEthernet0/1
O 192.168.4.64/28 [110/20] via 172.16.1.1, 00:08:12, GigabitEthernet0/0

Which route will the router select to forward the packet?

Show answer & explanation

Answer: The OSPF route 192.168.4.64/28 via 172.16.1.1 because it provides the longest matching prefix for the destination IP address.

Answer

The router selects the OSPF route `192.168.4.64/28` via 172.16.1.1 because it provides the longest prefix match (/28) for the destination IP address 192.168.4.66.
When a router receives a packet, it compares the destination IP address against all routes in its routing table. When multiple routes match the destination IP address, the router selects the route with the longest prefix length (most network bits / longest subnet mask). In this case, 192.168.4.66 matches all four prefixes, but the /28 route is the most specific match (28 bits vs 27, 26, or 24 bits). Administrative distance plays no role here because the prefixes are of different lengths.

Step-by-Step Solution

1
Identify the destination IP address of the incoming packet
Destination IP is 192.168.4.66
Routing lookup is driven by matching the packet's destination IP against routing table entries.
2
Determine which routing table prefixes encompass the destination IP address
192.168.4.0/24 (range .0-.255), 192.168.4.64/26 (range .64-.127), 192.168.4.64/27 (range .64-.95), and 192.168.4.64/28 (range .64-.79) all match the destination address 192.168.4.66.
All four configured subnets contain the IP address 192.168.4.66.
3
Apply the Longest Prefix Match (LPM) rule
The /28 prefix length (28 subnet bits) is the longest and most specific match compared to /27, /26, and /24.
Cisco routers always prioritize the most specific route (longest subnet mask) when forwarding traffic.

Key Concept

Longest Prefix Match (LPM) in IPv4 Route Determination
Estimated Time:1m 0s
Question 451Question →

A network administrator needs to direct traffic destined specifically for a single log server at 192.168.10.45192.168.10.45 through next-hop IPv4 address 10.1.1.210.1.1.2, while allowing all other traffic intended for the 192.168.10.0/24192.168.10.0/24 subnet to follow the existing default path. Which Cisco IOS command must be configured on the router to accomplish this requirement?

Show answer & explanation

Answer: ip route 192.168.10.45 255.255.255.255 10.1.1.2

Answer

The command 'ip route 192.168.10.45 255.255.255.255 10.1.1.2' creates a host static route targeting the specific destination IP address.
The correct command uses a subnet mask of 255.255.255.255 (/32) combined with the exact host IP address 192.168.10.45. When the router performs forwarding lookup, the longest prefix match rule ensures that packets addressed to 192.168.10.45 match this 32-bit route rather than broader subnet routes.

Step-by-Step Solution

1
Identify the routing requirement
Only traffic to the single IP host 192.168.10.45 must take the specific next-hop path 10.1.1.2.
Traffic to other hosts within the 192.168.10.0/24 subnet must follow another path, requiring a route that applies only to a single IP address.
2
Determine the subnet mask required for a host route
A 32-bit mask (255.255.255.255255.255.255.255) specifies exactly one IPv4 host address.
In IPv4 routing, a /32 prefix mask indicates that all 32 bits of the destination IPv4 address must match.
3
Construct the Cisco IOS static route command
ip route 192.168.10.45 255.255.255.255 10.1.1.2
The standard syntax is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip>'.

Key Concept

IPv4 Host Static Routing and Longest Prefix Match
Estimated Time:1m 0s
Question 452Question →

A network administrator is configuring redundant internet connectivity on an edge router. The primary ISP connection is reachable via next-hop IPv4 address 203.0.113.1203.0.113.1, while a secondary backup ISP connection is reachable via next-hop IPv4 address 198.51.100.1198.51.100.1. The administrator must configure a primary default static route and a floating backup default static route so that the backup link is utilized only when the primary link fails. Which TWO commands must be configured on the router to fulfill these requirements?

Select all that apply

Show answer & explanation

Answer: ip route 0.0.0.0 0.0.0.0 203.0.113.1; ip route 0.0.0.0 0.0.0.0 198.51.100.1 210

Answer

The router requires two default static routes: one primary route pointing to next-hop 203.0.113.1 using default administrative distance 1 ('ip route 0.0.0.0 0.0.0.0 203.0.113.1'), and one floating static route pointing to next-hop 198.51.100.1 with an administrative distance higher than 1 ('ip route 0.0.0.0 0.0.0.0 198.51.100.1 210').
To establish a primary default static route and a floating backup default static route, the primary path must be configured with a lower administrative distance (default is 1) pointing to 203.0.113.1, and the backup path must be configured with an administrative distance strictly higher than 1 (such as 210) pointing to 198.51.100.1. The router installs the route with the lower administrative distance into the routing table under normal operations. If the primary interface or path fails, the route with administrative distance 210 becomes active.

Step-by-Step Solution

1
Define the primary default static route destination prefix and next-hop address.
Construct the command 'ip route 0.0.0.0 0.0.0.0 203.0.113.1', which defaults to administrative distance 1.
Default static routes use prefix 0.0.0.0 and mask 0.0.0.0 to match any IPv4 destination not explicitly present in the routing table.
2
Configure the secondary floating default static route with a higher administrative distance.
Append an administrative distance value greater than 1 (such as 210) to the secondary next-hop command: 'ip route 0.0.0.0 0.0.0.0 198.51.100.1 210'.
A floating static route remains inactive in the routing table until the lower administrative distance primary route disappears.

Key Concept

Floating Static Route Configuration and Administrative Distance
Question 453Question →

Two Cisco routers are directly connected through an Ethernet switch on the 192.168.10.0/24 subnet and are currently operating in OSPFv2 Area 0 using default Ethernet interface settings. A network engineer enters the interface configuration mode on both routers and executes the command `ip ospf network point-to-point`. Which statement correctly describes the operational impact of this configuration change on the link?

Show answer & explanation

Answer: OSPFv2 will suppress Designated Router (DR) and Backup Designated Router (BDR) elections while preserving neighbor adjacency.

Answer

OSPFv2 will suppress Designated Router (DR) and Backup Designated Router (BDR) elections while preserving neighbor adjacency.
When an OSPF interface is explicitly configured as a point-to-point network type (`ip ospf network point-to-point`), OSPF recognizes that only two devices share the link. Consequently, Designated Router (DR) and Backup Designated Router (BDR) elections are bypassed, streamlining neighbor relationships while maintaining normal multicast OSPF communications and full adjacency.

Step-by-Step Solution

1
Identify default OSPF network type behavior on Ethernet interfaces
By default, Ethernet interfaces operate as Broadcast multiaccess networks, requiring DR and BDR elections.
Broadcast networks use DR/BDR roles to minimize adjacency count and LSA flooding over multiaccess media.
2
Analyze the effect of configuring `ip ospf network point-to-point`
Changing the network type to point-to-point informs OSPF that exactly two routers are connected on the segment.
Since only two routers share the link, DR and BDR elections are unnecessary and are bypassed.
3
Verify timer compatibility between default broadcast and point-to-point network types
Both broadcast and point-to-point types use a 10-second Hello timer and a 40-second Dead timer.
Because timers match on both ends, neighbor adjacencies form and remain stable in the FULL state.

Key Concept

OSPFv2 Point-to-Point Network Type Characteristics and DR/BDR Elimination
Question 454Question →

A network administrator intends to deploy a floating static route on router R1 as a backup path for the internal network 172.16.50.0/24172.16.50.0/24. The primary path to this destination is currently learned through internal EIGRP (default Administrative Distance of 9090). During initial testing, the administrator notices that traffic destined for 172.16.50.0172.16.50.0 is immediately taking the static backup path across interface GigabitEthernet0/2, even though the primary EIGRP neighbor relationship remains active and healthy. Which two issues could cause the static route to be preferred over the active EIGRP route? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: The administrator configured the floating static route with an Administrative Distance of 8080.; The static route was configured using a destination prefix of 172.16.50.0/25172.16.50.0/25 instead of 172.16.50.0/24172.16.50.0/24.

Answer

The static route is preferred over the primary EIGRP route if the static route was configured with an Administrative Distance of 80 (which is lower than EIGRP's default Administrative Distance of 90) or if the static route was configured with a more specific subnet mask of /25 (which takes precedence due to the Longest Prefix Match rule).
A floating static route functions as a backup path only when its Administrative Distance (AD) is strictly higher than that of the primary routing protocol (internal EIGRP default AD = 90). Configuring an AD of 80 causes the static route to preempt EIGRP. Additionally, routers prioritize routes based on Longest Prefix Match before AD; configuring a /25 route creates a more specific entry than the /24 EIGRP route, forcing traffic onto the static path.

Step-by-Step Solution

1
Evaluate the role of Administrative Distance (AD) in route selection.
Cisco IOS routing tables prioritize routes with lower AD values. Internal EIGRP has a default AD of 90. If a static route is configured with AD 80, it overrides the EIGRP route.
Floating static routes must have an AD higher than the primary routing protocol to stay in standby mode.
2
Evaluate the forwarding decision order between Longest Prefix Match and AD.
Routers first match packets using the longest (most specific) network prefix mask. A /25 prefix is more specific than a /24 prefix.
If the destination mask is /25, the router selects that route prior to comparing AD against the /24 EIGRP route.

Key Concept

Floating Static Route Administration and Prefix Matching
Estimated Time:1m 30s
Question 455Question →

A network administrator is evaluating protocol mechanics between HSRPv2 and VRRPv3 for deployment across an enterprise distribution block. Which two operational statements regarding virtual IP assignment, multicast transport, and protocol behaviors are accurate? (Select two.)

Select all that apply

Show answer & explanation

Answer: VRRP permits the virtual IPv4 address to be identical to the physical IPv4 address assigned to the Master router's interface, whereas HSRP requires the virtual IP address to be unique and distinct from any physical IPv4 address assigned to participating routers.; HSRPv2 transmits hello packets using UDP port 1985 to multicast IPv4 address 224.0.0.102, whereas VRRPv3 encapsulation uses IP protocol number 112 destined to multicast IPv4 address 224.0.0.18.

Answer

The two correct statements are: (1) VRRP permits the virtual IPv4 address to match the physical interface IP of the master router while HSRP requires a distinct virtual IP address, and (2) HSRPv2 uses UDP port 1985 with destination multicast 224.0.0.102, whereas VRRPv3 uses IP protocol 112 with destination multicast 224.0.0.18.
VRRP allows IP address ownership (where the virtual IP is identical to the physical IP address of the master interface), while HSRP requires the virtual IP to be a distinct IP address on the subnet. Additionally, HSRPv2 uses UDP port 1985 to multicast 224.0.0.102, whereas VRRPv3 operates over IP protocol 112 to multicast 224.0.0.18.

Step-by-Step Solution

1
Analyze virtual IP address assignment rules for HSRP vs VRRP.
VRRP supports IP address ownership where the virtual IP matches the master router's physical IP address (priority set to 255 automatically). HSRP requires the virtual IP to be an unassigned IP on the subnet, distinct from all participating routers' physical IPs.
Understanding IP address assignment mechanics prevents configuration errors during FHRP deployment.
2
Examine transport protocol encapsulation and multicast addresses.
HSRPv2 uses UDP port 1985 and multicast 224.0.0.102. VRRPv3 uses IP protocol 112 directly (no transport header like UDP/TCP) and multicast 224.0.0.18.
Differentiating transport mechanics is essential for access control list (ACL) and firewall configuration.
3
Evaluate default preemption behavior differences.
HSRP disables preemption by default, whereas VRRP enables preemption by default.
Recognizing default preemption behaviors avoids unexpected routing mastership shifts.

Key Concept

HSRPv2 vs VRRPv3 protocol characteristics, transport mechanisms, preemption defaults, and virtual IP allocation rules
Question 456Question →

An administrator examines the following routing table output from a Cisco router:

text
Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D 10.10.20.0/24 [90/2170112] via 192.168.1.2, 00:15:42, GigabitEthernet0/0
O 10.10.20.0/26 [110/20] via 192.168.1.6, 00:08:12, GigabitEthernet0/1
S 10.10.0.0/16 [1/0] via 192.168.1.10
C 10.10.20.128/25 is directly connected, GigabitEthernet0/2

If the router receives a packet with a destination IP address of 10.10.20.45, which two statements correctly describe how the router processes this packet? (Select two.)

Select all that apply

Show answer & explanation

Answer: The router forwards the packet out GigabitEthernet0/1 because the prefix 10.10.20.0/26 represents the longest matching prefix for the destination IP address.; The router evaluates administrative distance only among routes that share the exact same longest prefix match length.

Answer

The router selects the OSPF route (10.10.20.0/26) and forwards the packet out interface GigabitEthernet0/1 because 26 bits is the longest matching prefix for host 10.10.20.45. Administrative distance is only evaluated when multiple routing protocols advertise the exact same destination network prefix length.
The destination address 10.10.20.45 matches three routes in the routing table: 10.10.0.0/16, 10.10.20.0/24, and 10.10.20.0/26. Router forwarding logic mandates that the route with the longest matching prefix (/26) is chosen first. Consequently, the packet is egressed out interface GigabitEthernet0/1. Furthermore, administrative distance is only referenced when comparing multiple sources advertising the exact same network prefix and subnet mask.

Step-by-Step Solution

1
Determine which routing table entries match the destination IP address 10.10.20.45.
Three entries match: 10.10.0.0/16 (range 10.10.0.0-10.10.255.255), 10.10.20.0/24 (range 10.10.20.0-10.10.20.255), and 10.10.20.0/26 (range 10.10.20.0-10.10.20.63). Entry 10.10.20.128/25 does not match.
Routing decision logic requires evaluating all active prefix matches for a given destination host address.
2
Apply the Longest Prefix Match (LPM) rule among matching routes.
The route 10.10.20.0/26 has the longest prefix length (/26 > /24 > /16).
Routers always select the route with the most specific (longest) subnet mask before comparing administrative distance.
3
Identify the forwarding interface and understand administrative distance behavior.
Packet is egressed via GigabitEthernet0/1. Administrative distance is only compared when identical prefixes with identical mask lengths exist from different protocol sources.
Administrative distance compares routing protocol reliability for the same prefix, not across prefixes of different specificity.

Key Concept

Longest Prefix Match Rule vs. Administrative Distance
Question 457Question →

An engineer is troubleshooting a first-hop redundancy deployment on a Cisco router interface configured with IPv4 address 192.168.100.1/24. When entering the command `standby 1 ip 192.168.100.1`, the CLI outputs `% HSRP: Bad IP address 192.168.100.1`. However, on a neighboring router running VRRP, assigning the physical interface IP address as the virtual IP address is accepted and functions correctly. What fundamental operational difference between HSRP and VRRP causes this behavioral discrepancy?

Show answer & explanation

Answer: HSRP mandates that the virtual IP address must be unique and cannot match any physical interface IP in the standby group, whereas VRRP supports IP address ownership where the master router physical IP serves as the virtual IP.

Answer

HSRP mandates that the virtual IP address must be unique and cannot match any physical interface IP in the standby group, whereas VRRP supports IP address ownership where the master router physical IP serves as the virtual IP.
In HSRP protocol operations, the virtual IP address MUST be distinct from any physical IPv4 address assigned to the interfaces participating in the HSRP group. Attempting to assign the physical interface IP as the HSRP virtual IP results in a CLI validation error (`% HSRP: Bad IP address`). Conversely, VRRP (RFC 3768 / RFC 5798) explicitly permits IP address ownership, allowing the physical interface IP of the master router to function as the virtual gateway IP address (setting the router priority to 255).

Step-by-Step Solution

1
Analyze the CLI error output: `% HSRP: Bad IP address 192.168.100.1`.
Identify that the Cisco IOS CLI rejects HSRP configuration when attempting to set the virtual IP equal to the physical interface IP.
Cisco HSRP (both version 1 and version 2) requires the virtual IP to be a separate, unique IPv4 address within the same subnet, distinct from all physical interface IPs assigned to participating routers.
2
Compare HSRP rules with VRRP rules regarding Virtual IP assignment.
Recognize that VRRP allows IP address ownership (where the Virtual IP address matches the physical interface IP address of the Master router).
When a VRRP router owns the IP address, its priority is automatically elevated to 255, making it the VRRP Master.
3
Evaluate the option choices to select the statement accurately explaining this architectural difference.
Select the statement highlighting that HSRP requires a unique virtual IP while VRRP supports IP address ownership.
This correctly identifies why HSRP produced an error while VRRP accepted the physical IP address.

Key Concept

HSRP vs. VRRP Virtual IP Address Ownership and Assignment Rules
Estimated Time:1m 30s
Question 458Question →

A network engineer initializes OSPFv2 on a Cisco router with process ID 10. The router interfaces are configured with the following parameters and operational states:

- Loopback 0: 10.10.10.1/32 (administratively down, line protocol down)
- Loopback 1: 172.16.10.1/32 (up, line protocol up)
- GigabitEthernet 0/0: 192.168.10.254/24 (up, line protocol up)
- GigabitEthernet 0/1: 192.168.20.1/24 (up, line protocol up)

No explicit `router-id` command has been configured under the OSPF routing process. Which TWO statements accurately describe the OSPF Router ID selection and operational behavior for this router?

Select all that apply

Show answer & explanation

Answer: The OSPF process selects 172.16.10.1 as its Router ID because it is the highest IPv4 address among operational loopback interfaces.; The router maintains 172.16.10.1 as its active OSPF Router ID even if Loopback 1 is subsequently shut down, until the OSPF process is reset or reloaded.

Answer

The OSPF process selects 172.16.10.1 as its Router ID because it is the highest IPv4 address among operational loopback interfaces, and it maintains 172.16.10.1 as its active OSPF Router ID even if Loopback 1 is subsequently shut down, until the OSPF process is reset or reloaded.
OSPFv2 selects its Router ID following a strict hierarchy: first an explicit `router-id` configuration, second the highest IPv4 address among operational (up/up) loopback interfaces, and third the highest IPv4 address among operational physical interfaces. Because Loopback 0 is down, Loopback 1 (172.16.10.1) is chosen as the highest active loopback IP address, taking precedence over physical interfaces. Furthermore, OSPF Router ID selection is non-preemptive; once selected, changes to interface states do not immediately update the running Router ID without explicitly resetting the OSPF process.

Step-by-Step Solution

1
Evaluate the order of precedence for OSPFv2 Router ID election.
Order: 1. Manually configured `router-id` under `router ospf`. 2. Highest IPv4 address on an active (up/up) loopback interface. 3. Highest IPv4 address on an active (up/up) physical interface.
Since no manual `router-id` command is present, the process moves to checking operational loopback interfaces.
2
Filter interfaces by operational status (up/up).
Loopback 0 is down and disqualified. Loopback 1 (172.16.10.1), GigabitEthernet 0/0 (192.168.10.254), and GigabitEthernet 0/1 (192.168.20.1) are operational.
Only active interfaces with operational line protocol up can be selected.
3
Determine the winning interface IP address.
Loopback 1 (172.16.10.1) is selected because it is the only active loopback interface, overriding higher IP addresses on physical interfaces.
Loopback interfaces always take precedence over non-loopback interfaces.
4
Analyze non-preemptive behavior of the OSPF Router ID.
Once elected, the Router ID remains stable in memory. Shutting down the interface or adding higher IP addresses does not automatically change the active Router ID until `clear ip ospf process` or a device reload occurs.
OSPF Router ID selection is non-preemptive to prevent unnecessary adjacency tear-downs.

Key Concept

OSPFv2 Router ID Election Priority and Non-Preemptive Stability Mechanics
Question 459Question →

A network administrator configures the command `ip ospf network point-to-point` on a GigabitEthernet interface of a Cisco router connected to a switch segment with another router. Previously, the interface operated using default OSPFv2 interface parameters for Ethernet interfaces. Which two operational changes occur on this interface as a result of this configuration change? (Select two.)

Select all that apply

Show answer & explanation

Answer: OSPF halts the election of Designated Router (DR) and Backup Designated Router (BDR) roles on the interface.; Routers on the segment stop sending and listening to packets on the AllDRouters multicast address (224.0.0.6).

Answer

Configuring an Ethernet interface as an OSPF point-to-point network type stops the DR/BDR election process on that interface and disables the use of the AllDRouters multicast destination address (224.0.0.6).
When an Ethernet interface is converted to an OSPF point-to-point network type, OSPF bypasses the DR and BDR election phase completely because the topology assumes a direct link between two routers. Because no DR or BDR exists, non-DR routers no longer send packets to the 224.0.0.6 (AllDRouters) multicast address; all OSPF control packets are sent exclusively to 224.0.0.5 (AllSPFRouters).

Step-by-Step Solution

1
Identify the default OSPF network type for Ethernet interfaces.
Ethernet interfaces defaults to the Broadcast multiaccess network type, which elects a DR and BDR and uses multicast address 224.0.0.6 for non-DR routers to communicate with the DR/BDR.
Broadcast multiaccess networks reduce adjacencies on shared segments via DR/BDR routers.
2
Analyze the impact of changing the network type to Point-to-Point using `ip ospf network point-to-point`.
Point-to-point network types assume exactly two nodes on the link. Consequently, OSPF DR/BDR election is suppressed, and communication over 224.0.0.6 is disabled since DR/BDR roles are absent.
Point-to-point links form direct peer adjacencies without intermediate designated routers.
3
Evaluate timer and neighbor discovery settings for Point-to-Point interfaces.
Hello/Dead timers remain at 10/40 seconds, and dynamic neighbor discovery using AllSPFRouters (224.0.0.5) is maintained.
Timers only change to 30/120 seconds on Non-Broadcast Multi-Access (NBMA) and Point-to-Multipoint network types.

Key Concept

OSPF Network Types (Broadcast vs. Point-to-Point) and DR/BDR Operational Differences
Question 460Question →

A network device attempts to forward an IP packet toward the target address 172.31.25.140. The routing table contains four matching prefix entries:

- 172.31.25.0/24 [1/0] via 10.1.1.1
- 172.31.25.128/26 [90/307200] via 10.2.2.2
- 172.31.25.128/27 [110/40] via 10.3.3.3
- 172.31.25.136/29 [120/4] via 10.4.4.4

Which next-hop IP address will the device select to forward this packet?

Show answer & explanation

Answer: 10.4.4.4

Answer

The router forwards the packet to next-hop address 10.4.4.4 because 172.31.25.136/29 has the longest matching prefix length (/29).
When a router receives a packet, it compares the destination IP address against all entries in its routing table and selects the route with the longest matching prefix length (the most specific subnet mask). Here, 172.31.25.136/29 matches 172.31.25.140 with a 29-bit prefix length, which is longer than /27, /26, or /24. The next-hop associated with this route is 10.4.4.4.

Step-by-Step Solution

1
Determine which routing entries match destination IP 172.31.25.140.
All four routes (172.31.25.0/24, 172.31.25.128/26, 172.31.25.128/27, and 172.31.25.136/29) contain the IP address 172.31.25.140 within their range.
For 172.31.25.136/29, the usable IP host range spans 172.31.25.137 through 172.31.25.142, which includes 172.31.25.140.
2
Compare the prefix lengths of all matching routes.
The prefix lengths are /24, /26, /27, and /29.
Routers use the Longest Prefix Match (LPM) rule to select the forwarding route regardless of Administrative Distance.
3
Select the route with the highest prefix length (most specific mask).
/29 is the longest prefix match, corresponding to route 172.31.25.136/29 via 10.4.4.4.
Administrative distance is only evaluated when comparing identical prefixes from different routing sources. For different prefix lengths, LPM always governs.

Key Concept

Longest Prefix Match (LPM)
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