IP Connectivity

493 questions

All types493 Multiple choice250 Multiple select113 Matching25 Ordering60 Fill in the blank22 Short answer23

A network engineer is configuring a static route on a Cisco router interface connected to a broadcast multiaccess Ethernet network. If the engineer configures the command using only the egress interface (e.g., `ip route 10.20.30.0 255.255.255.0 GigabitEthernet0/0`) without specifying a next-hop IPv4 address, which network behavior or operational issue will occur?

The router automatically assigns an administrative distance of 255 to the route, preventing it from being installed in the routing table.

The router treats the destination subnet as directly connected and generates an ARP request for every destination IP address, leading to high CPU load and ARP table bloat.

The router drops incoming packets destined for 10.20.30.0/24 because static routes on Ethernet interfaces strictly mandate a recursive lookup using a loopback IP address.

The static route functions identically to specifying a next-hop IPv4 address because Ethernet interfaces automatically resolve the next-hop MAC address using CDP.

Show answer & explanation

Answer: The router treats the destination subnet as directly connected and generates an ARP request for every destination IP address, leading to high CPU load and ARP table bloat.

Answer

The router treats the destination prefix as a directly connected subnet on the Ethernet segment and attempts to perform an ARP lookup for every host IP address in that destination network.

When an IPv4 static route on a broadcast multiaccess Ethernet interface specifies only the exit interface, Cisco IOS considers the destination prefix directly connected. Consequently, the router attempts to resolve the MAC address for every individual destination IP address in that subnet via ARP requests. This leads to severe ARP table growth, high CPU usage, and dependence on Proxy ARP.

Step-by-Step Solution

Analyze the static route syntax used on a multiaccess broadcast interface.

The command specifies an exit interface (`GigabitEthernet0/0`) instead of a next-hop IPv4 address.

On point-to-point links (like HDLC/PPP serial), an exit interface is sufficient because there is only one possible recipient. On multiaccess Ethernet networks, multiple devices share the segment.

Determine how the router processes packet forwarding for an exit-interface-only static route on Ethernet.

The router considers the target subnet directly connected to `GigabitEthernet0/0`.

To forward a packet, the router must encapsulate it into an Ethernet frame requiring a destination MAC address. Because no next-hop IP was defined, the router broadcasts an ARP request asking for the MAC address of the final destination IP address.

Identify the operational consequences of this configuration.

Excessive ARP traffic, enlarged ARP table size, and elevated CPU utilization occurs.

Every unique destination IPv4 address triggers a separate ARP request. Unless Proxy ARP is enabled on the downstream gateway, traffic will fail completely; if Proxy ARP is enabled, the router's ARP table fills with individual host entries.

Key Concept

Static Route Exit Interface vs. Next-Hop IP on Multiaccess Broadcast Networks

Question 482Question →

A network administrator is monitoring an HSRP deployment on router R1 and executes the `show standby brief` command, obtaining the following output:

text
Interface Grp Pri P State Active Standby Virtual IP
Gi0/1 20 110 P Active local 192.168.20.3 192.168.20.1

Router R1 is configured to track interface GigabitEthernet0/0 with a priority decrement value of $20$ . Router R2 (currently the Standby router at $192.168.20.3$ ) has an HSRP priority of $100$ and has preemption enabled.

If interface GigabitEthernet0/0 on router R1 goes down, which operational change occurs on the local network segment?

Router R1's priority drops to

90

, causing Router R2 to preempt R1 and assume the Active role for HSRP group 20.

Router R1 remains the Active router because priority tracking decrements only trigger syslog alerts without changing active gateway ownership.

Router R1's priority drops to

90

, but Router R1 remains Active because a Standby router cannot preempt unless its priority exceeds the initial configured priority of

110

Router R1 automatically changes its virtual IP address to

192.168.20.3

to match the IP address of the Standby router.

Show answer & explanation

Answer: Router R1's priority drops to $90$ , causing Router R2 to preempt R1 and assume the Active role for HSRP group 20.

Answer

Router R1's priority drops to

90

, causing Router R2 to preempt R1 and assume the Active role for HSRP group 20.

When the tracked interface GigabitEthernet0/0 fails on router R1, HSRP interface tracking decrements R1's active priority by

20

, reducing it from

110

90

. Standby router R2 has a priority of

100

and preemption enabled. Because R2's priority (

100

) is now higher than R1's current priority (

90

), R2 preempts R1 and transitions to the Active state.

Step-by-Step Solution

Calculate Router R1's updated priority following the tracked interface failure.

Initial priority (

110

) minus decrement (

20

) =

90

HSRP interface tracking reduces the local priority by the specified decrement value when the tracked interface enters a down state.

Compare Router R1's new priority against Router R2's priority.

Router R1 priority (

90

) < Router R2 priority (

100

Router R2 now has a higher priority than Router R1 on the HSRP segment.

Evaluate preemption settings on Router R2 to determine state transition.

Router R2 preempts Router R1, becoming Active, while Router R1 transitions to Standby.

Because Router R2 has preemption enabled, it immediately takes over the Active role once its priority exceeds the current Active router's priority.

Key Concept

HSRP Interface Tracking and Preemption Failover Dynamics

Estimated Time:1m 30s

Question 483Question →

An administrator is configuring a secondary IPv4 static route on router R1 to reach network $10.50.0.0/16$ via next-hop $192.168.2.2$ . A primary static route to the same destination network via next-hop $192.168.1.2$ already exists in the active configuration with default settings. The secondary route must serve strictly as a backup and only enter the routing table if the primary path fails. Which Cisco IOS command should be configured on router R1?

ip route 10.50.0.0 255.255.0.0 192.168.2.2 10

ip route 10.50.0.0 255.255.0.0 192.168.2.2 1

ip route 10.50.0.0 255.255.0.0 192.168.2.2 0

ip route 10.50.0.0 255.255.0.0 192.168.2.2

Show answer & explanation

Answer: ip route 10.50.0.0 255.255.0.0 192.168.2.2 10

Answer

The correct command is `ip route 10.50.0.0 255.255.0.0 192.168.2.2 10`.

The command configuring an administrative distance of 10 creates a floating static route. Because Cisco IOS static routes default to an administrative distance of 1, setting the backup route's distance to 10 ensures it remains inactive until the primary route fails.

Step-by-Step Solution

Identify the administrative distance of the existing primary static route.

Standard static routes configured without an explicit distance parameter use a default administrative distance (AD) of

1

Administrative distance determines route trustworthiness in the Cisco IOS routing table.

Determine the required administrative distance for a floating static backup route.

The backup route must have an AD strictly greater than

1

(such as

10

Routes with higher AD values are ignored by the routing engine until all lower-AD routes for the identical prefix become unreachable.

Construct the Cisco IOS static route command syntax incorporating the distance parameter.

Syntax: `ip route <prefix> <mask> <next-hop> <distance>`. Applying parameters yields `ip route 10.50.0.0 255.255.0.0 192.168.2.2 10`.

Appending an administrative distance higher than

1

creates a floating static route.

Key Concept

Floating static routes rely on configuring an Administrative Distance higher than the primary routing source so that the backup route remains dormant in the configuration until the primary route drops out of the routing table.

Estimated Time:1m 30s

Question 484Question →

A network administrator is evaluating the operational parameters and default behaviors of First Hop Redundancy Protocols (FHRP) on Cisco IOS devices. Which two statements accurately describe default differences between VRRPv2 and HSRPv1?

Select all that apply

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

VRRPv2 uses the destination multicast IP address 224.0.0.18, whereas HSRPv1 uses 224.0.0.2.

HSRPv1 permits the configured virtual IP address to match a physical interface IP address on a participating router, whereas VRRP prohibits this configuration.

VRRP Master routers transmit advertisement packets every 3 seconds by default, whereas HSRP Active routers transmit hello packets every 1 second by default.

Show answer & explanation

Answer: VRRP preemption is enabled by default, whereas HSRP preemption is disabled by default.; VRRPv2 uses the destination multicast IP address 224.0.0.18, whereas HSRPv1 uses 224.0.0.2.

Answer

VRRP preemption is enabled by default while HSRP preemption is disabled by default, and VRRPv2 utilizes destination multicast address 224.0.0.18 while HSRPv1 utilizes 224.0.0.2.

VRRPv2 operates with preemption enabled by default and sends advertisements to multicast IP address 224.0.0.18. In contrast, HSRPv1 has preemption disabled by default (requiring explicit configuration) and sends hello messages to multicast IP address 224.0.0.2.

Step-by-Step Solution

Analyze preemption default settings for both protocols.

VRRP automatically enables preemption so that a router with higher priority assumes the Master role without manual CLI intervention. HSRP defaults to preemption disabled, requiring the 'standby <group> preempt' command.

Understanding protocol default behaviors is essential for predicting failover performance.

Analyze multicast addressing and transport mechanisms.

VRRPv2 uses multicast address 224.0.0.18 over IP protocol 112. HSRPv1 uses multicast address 224.0.0.2 over UDP port 1985.

Differentiating control plane encapsulation helps when analyzing packet captures or ACL filter requirements.

Evaluate IP address ownership rules.

VRRP supports IP address ownership where the virtual IP matches a router interface IP (priority 255). HSRP explicitly forbids assigning an active physical IP address as the virtual IP address.

Misinterpreting IP assignment rules causes CLI configuration errors when setting up HSRP virtual gateways.

Key Concept

HSRP and VRRP Feature and Default Parameter Comparison

Question 485Question →

A network administrator is migrating a gateway configuration from VRRP to HSRP Group 1 on a Cisco router. Under the previous VRRP setup, the virtual IP address was configured to match the physical IPv4 address of router R1's GigabitEthernet0/1 interface (192.168.10.1/24). The administrator attempts to enter the command `standby 1 ip 192.168.10.1` under interface GigabitEthernet0/1 on R1. What is the outcome of executing this command on Cisco IOS?

The router accepts the command and automatically sets R1's HSRP priority to 255 to designate it as the IP address owner.

Cisco IOS rejects the command because HSRP virtual IP addresses must be distinct from any physical IP address configured on the router interfaces.

The router accepts the command, but R1 remains permanently in the Speak state due to a virtual IP conflict.

The command is accepted only if preemption is manually disabled prior to executing the virtual IP assignment.

Show answer & explanation

Answer: Cisco IOS rejects the command because HSRP virtual IP addresses must be distinct from any physical IP address configured on the router interfaces.

Answer

Cisco IOS rejects the command because HSRP virtual IP addresses must be distinct from any physical IP address configured on the router interfaces.

In Cisco IOS HSRP implementation, the virtual IP address must be an unassigned IP within the local subnet and cannot match the physical IP address of any participating router interface. Attempting to set the HSRP virtual IP to the router interface's physical IP results in an immediate CLI configuration error.

Step-by-Step Solution

Analyze the operational differences regarding Virtual IP selection between VRRP and HSRP.

VRRP supports assigning an interface's physical IP address as the virtual IP (making that router the IP address owner with priority 255). HSRP does not support this and mandates an unused IP address within the subnet.

Understanding protocol specification constraints prevents configuration errors during migration.

Evaluate the Cisco IOS command behavior when attempting to assign a physical interface IP to an HSRP group.

Cisco IOS returns a configuration error stating that the virtual IP cannot be the same as the interface IP address.

HSRP requires a distinct virtual IP address to function correctly across active and standby nodes.

Key Concept

HSRP Virtual IP Addressing Rules vs VRRP IP Address Ownership

Question 486Question →

A network administrator needs to configure and verify a floating static route for destination network $172.16.20.0/24$ via next-hop IP $10.2.2.2$ on a Cisco router. The primary path to this network is currently learned dynamically via EIGRP with an Administrative Distance of $90$ . Place the configuration and verification steps in the correct sequential order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequential process is: Enter global configuration mode -> Configure the floating static route with AD 100 -> Verify the routing table to ensure the route is inactive during normal operation -> Shut down the primary interface to trigger failover -> Re-verify the routing table to confirm the floating static route becomes active.

The correct order follows standard Cisco IOS workflow: configuring global settings first, adding the floating static route with an AD higher than EIGRP (90), verifying that the route is inactive during normal operation, simulating a link failure by shutting down the primary interface, and finally verifying that the floating static route takes over as the active path in the routing table.

Step-by-Step Solution

Enter global configuration mode

The CLI prompt changes to global configuration mode (`Router(config)#`).

Static routing commands (`ip route`) can only be entered in global configuration mode.

Configure the backup static route

The floating static route with Administrative Distance 100 is written to the running configuration.

Configuring an Administrative Distance of 100 ensures the static route has a higher distance than EIGRP (AD 90), keeping it out of the routing table during normal operation.

Verify initial routing table state

The output of `show ip route` lists only the EIGRP route for

172.16.20.0/24

Cisco IOS selects routes with the lowest Administrative Distance for the Routing Information Base (RIB); thus, the floating static route must remain hidden while EIGRP is healthy.

Simulate primary path failure

The primary interface enters the administratively down state, invalidating and removing the primary EIGRP route from the RIB.

Interface shutdown removes dependent routes, prompting the router to evaluate alternative routes for the destination.

Verify post-failover routing table state

The output of `show ip route` shows

172.16.20.0/24

reachable via static route next-hop

10.2.2.2

With the primary route removed, the floating static route becomes the best remaining path and is installed into the active routing table.

Key Concept

Floating static route configuration, administrative distance precedence, and failover verification.

Estimated Time:1m 30s

Question 487Question →

Place the HSRP (Hot Standby Router Protocol) router states in the correct chronological order as a newly configured router transitions from initial startup to becoming the active gateway.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of HSRP states from startup to active gateway is Initial, Listen, Speak, Standby, and Active.

During standard HSRP election and initialization, a router follows a strict 5-state progression: Initial (interface up), Listen (receiving peer Hello packets), Speak (actively sending Hello packets to compete in election), Standby (elected as primary backup), and Active (forwarding virtual IP traffic).

Step-by-Step Solution

Identify the initial configuration state upon interface activation.

Initial state is the first phase.

The protocol begins in Initial state when HSRP is first enabled or when an interface changes state to UP.

Determine the passive monitoring state prior to active participation.

Listen state comes second.

The router must first listen for existing active/standby Hello packets to determine if a gateway is already elected.

Identify when the router starts transmitting Hello messages.

Speak state comes third.

Once the router gathers initial group information, it enters Speak state to transmit Hello messages and enter the election.

Identify the election outcome role prior to active status.

Standby state comes fourth.

If the router has a higher priority than other non-active routers, it becomes the Standby router candidate.

Identify the final operational state responsible for packet forwarding.

Active state is the final phase.

The router transitions to Active state to process traffic sent to the virtual MAC and virtual IP address.

Key Concept

HSRP router state transitions and convergence lifecycle

Question 488Question →

A network engineer is comparing default operational behaviors between HSRPv1 and VRRPv2 across Cisco IOS switches. Which two statements accurately describe default characteristics and protocol specifications of these First Hop Redundancy Protocols? (Choose two.)

Select all that apply

VRRPv2 has preemption enabled by default, whereas HSRPv1 has preemption disabled by default.

HSRPv1 allows the virtual IP address to be configured using an IP address already assigned to a router's physical interface, whereas VRRPv2 explicitly rejects this configuration.

VRRPv2 generates virtual MAC addresses using the prefix 0000.5E00.01xx, whereas HSRPv1 uses the prefix 0000.0C07.ACxx.

HSRPv1 sends hello messages to multicast address 224.0.0.18, whereas VRRPv2 sends advertisements to multicast address 224.0.0.2.

Show answer & explanation

Answer: VRRPv2 has preemption enabled by default, whereas HSRPv1 has preemption disabled by default.; VRRPv2 generates virtual MAC addresses using the prefix 0000.5E00.01xx, whereas HSRPv1 uses the prefix 0000.0C07.ACxx.

Answer

The two correct statements are that VRRPv2 has preemption enabled by default while HSRPv1 has it disabled by default, and VRRPv2 uses virtual MAC addresses formatted as 0000.5E00.01xx while HSRPv1 uses 0000.0C07.ACxx.

VRRPv2 enables preemption by default and uses the virtual MAC prefix 0000.5E00.01xx. HSRPv1 disables preemption by default and uses the virtual MAC prefix 0000.0C07.ACxx.

Step-by-Step Solution

Evaluate default preemption state for HSRP and VRRP.

HSRPv1/v2 has preemption disabled by default (the active router remains active even if a higher-priority router joins). VRRPv2 has preemption enabled by default.

Protocol design choices differ regarding default failback behavior.

Analyze virtual MAC address structure for both protocols.

HSRPv1 uses 0000.0C07.ACxx, HSRPv2 uses 0000.0C9F.Fxxx, and VRRPv2 uses 0000.5E00.01xx.

Standardized virtual MAC ranges allow switches to map the virtual IP to unique Ethernet source/destination addresses.

Verify virtual IP matching constraints and multicast addresses.

VRRPv2 allows assigning a physical IP as virtual IP (IP address owner). HSRPv1 rejects assigning an interface's physical IP as the virtual IP. HSRPv1 uses multicast 224.0.0.2; VRRPv2 uses multicast 224.0.0.18.

Reversing these rules helps identify common misconceptions regarding protocol multicast endpoints and interface IP assignments.

Key Concept

HSRPv1 vs VRRPv2 Default Behaviors, Preemption, and Virtual Addressing

Question 489Question →

A Cisco router receives an IPv4 packet destined for $172.16.10.45$ . Place the routing table lookup and packet forwarding steps in the correct chronological order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct forwarding sequence begins with parsing the packet header to extract the destination IP, searching the routing table using longest prefix match logic, selecting the most specific matching prefix, identifying the next-hop IP or exit interface, and finally encapsulating the packet into a Layer 2 frame for egress transmission.

The correct order follows standard Cisco IOS router packet forwarding logic: extracting the destination IPv4 address, evaluating routing table prefixes, applying the longest prefix match (LPM) rule to select the best route, resolving the next-hop IP address or exit interface, and performing Layer 2 frame encapsulation prior to egress.

Step-by-Step Solution

Parse packet header

Destination IPv4 address extracted

The router requires the destination address to perform a routing lookup.

Perform routing table lookup

Candidate matching routes identified

The routing table contains network prefixes that must be checked against the destination IP.

Apply Longest Prefix Match (LPM)

Select most specific route entry

When multiple routes match the destination, the prefix with the most matching leading bits (longest subnet mask) is selected.

Resolve forwarding details

Determine next-hop IP address or egress interface

The selected route specifies the exact forwarding path towards the destination.

Layer 2 Encapsulation and Egress

Frame transmitted out the outbound interface

Layer 2 headers (such as Ethernet MAC headers) are constructed based on next-hop ARP table resolution before physical transmission.

Key Concept

IPv4 Routing Table Lookup and Longest Prefix Match Forwarding Logic

Question 490Question →

An engineer executes the following interface configuration on a Cisco IOS router:

text
R1(config)# interface GigabitEthernet0/0
R1(config-if)# ip address 10.1.1.1 255.255.255.0
R1(config-if)# standby 10 ip 10.1.1.1

What is the outcome of issuing the `standby 10 ip 10.1.1.1` command?

Cisco IOS rejects the command because HSRP virtual IP addresses cannot match the physical IP address assigned to an interface.

The command is accepted, and R1 automatically assumes the Active state with an operational priority of 255.

The command is accepted, but R1 remains stuck in the Speak state until a second router joins HSRP group 10.

The command is accepted, and Cisco IOS automatically enables HSRP preemption for group 10.

Show answer & explanation

Answer: Cisco IOS rejects the command because HSRP virtual IP addresses cannot match the physical IP address assigned to an interface.

Answer

Cisco IOS rejects the command because HSRP virtual IP addresses cannot match the physical IP address assigned to an interface.

In Hot Standby Router Protocol (HSRP), the virtual IP address must be unique within the subnet and cannot be identical to the physical IP address assigned to any interface of participating routers. When attempting to configure an HSRP virtual IP address that matches an existing interface IP address, Cisco IOS rejects the command with an explicit error.

Step-by-Step Solution

Analyze the interface IP configuration and the requested HSRP virtual IP.

The physical interface IP is set to 10.1.1.1/24, and the HSRP command attempts to assign 10.1.1.1 as the virtual IP address for HSRP group 10.

Identifying overlapping IP configurations is necessary to determine protocol compliance.

Compare HSRP rules against VRRP rules regarding IP address ownership.

In VRRP, a router can be the IP address owner and use its physical IP as the virtual IP (raising priority to 255). In HSRP, the virtual IP address MUST be an unused IP address within the subnet and cannot match any router's physical interface IP.

HSRP implementation rules require an unused virtual IP address on the subnet.

Determine CLI output behavior.

Cisco IOS displays an error message rejecting the `standby 10 ip 10.1.1.1` command.

Entering a matching IP address violates HSRP address assignment rules.

Key Concept

HSRP Virtual IP Address Constraints vs VRRP IP Owner Rules

Estimated Time:1m 0s

Question 491Question →

An enterprise router learns the path to a remote subnet $192.168.100.0/24$ through EIGRP, which operates with a default administrative distance of $90$ . A network engineer needs to configure a backup IPv4 static route to reach this subnet using the next-hop IPv4 address $10.0.5.2$ so that the backup route remains inactive until the primary EIGRP path fails. Which Cisco IOS command correctly configures this floating static route?

ip route 192.168.100.0 255.255.255.0 10.0.5.2 95

ip route 192.168.100.0 255.255.255.0 10.0.5.2 85

ip route 192.168.100.0 255.255.255.0 10.0.5.2 90

ip route 192.168.100.0 0.0.0.255 10.0.5.2 95

Show answer & explanation

Answer: ip route 192.168.100.0 255.255.255.0 10.0.5.2 95

Answer

The command 'ip route 192.168.100.0 255.255.255.0 10.0.5.2 95' correctly specifies a static route with an administrative distance higher than EIGRP's default AD of 90.

The correct command uses the syntax 'ip route 192.168.100.0 255.255.255.0 10.0.5.2 95'. Because an administrative distance of 95 is higher than EIGRP's default AD of 90, the router keeps this static route in reserve as a floating backup until the primary EIGRP path becomes unavailable.

Step-by-Step Solution

Identify the primary routing protocol's Administrative Distance (AD)

EIGRP internal routes have an AD of 90.

Floating static routes require an administrative distance strictly higher than the active primary routing source.

Determine the required AD for the floating static route

An administrative distance value greater than 90 (such as 95) is required.

Routes with lower AD values are preferred in the IP routing table. Setting AD > 90 ensures the route stays hidden until the primary route disappears.

Verify Cisco IOS static route syntax

Syntax: 'ip route <prefix> <mask> <next-hop-ip> [distance]'.

The subnet mask must be written in standard dotted-decimal format (255.255.255.0), followed by the next-hop IP and the custom AD value.

Key Concept

Floating Static Route Administrative Distance Selection

Question 492Question →

A network administrator is configuring IPv4 static routes on router R1 to reach destination network $10.88.0.0/16$ . The primary path must forward traffic to the next-hop IP address $192.168.50.2$ . A secondary path must act as a floating static backup route using the point-to-point interface Serial0/1/0, forwarding traffic only if the primary path becomes unavailable. Which TWO commands must be configured on router R1 to achieve this objective?

Select all that apply

ip route 10.88.0.0 255.255.0.0 192.168.50.2

ip route 10.88.0.0 255.255.0.0 Serial0/1/0 130

ip route 10.88.0.0 255.255.0.0 Serial0/1/0 1

ip route 10.88.0.0 0.0.255.255 192.168.50.2

Show answer & explanation

Answer: ip route 10.88.0.0 255.255.0.0 192.168.50.2; ip route 10.88.0.0 255.255.0.0 Serial0/1/0 130

Answer

The correct configurations are the command defining the primary static route using next-hop IP address 192.168.50.2 with the default administrative distance of 1, and the command defining the floating static backup route via interface Serial0/1/0 with an administrative distance elevated to 130.

The primary path to

10.88.0.0/16

is defined using the next-hop IPv4 address 192.168.50.2, which inherits the default static route Administrative Distance (AD) of 1. To configure a floating static backup route, an explicit AD value strictly greater than the primary route's AD (such as 130) must be appended at the end of the command string. Additionally, point-to-point interfaces like Serial0/1/0 are valid exit interface choices for static routing.

Step-by-Step Solution

Determine the primary route configuration.

Syntax: 'ip route 10.88.0.0 255.255.0.0 192.168.50.2'.

Standard IPv4 static routes default to an Administrative Distance (AD) of 1 when no distance parameter is specified at the end of the command.

Determine the backup floating static route configuration.

Syntax: 'ip route 10.88.0.0 255.255.0.0 Serial0/1/0 130'.

A floating static route requires an administrative distance higher than the primary route's AD (which is 1). Specifying an AD of 130 ensures it remains out of the routing table until the primary path goes down.

Key Concept

IPv4 Static Route Syntax and Floating Static Administrative Distance

Question 493Question →

Two Layer 3 switches, Core-1 and Core-2, provide default gateway redundancy for hosts in VLAN 30 ( $10.30.0.0/24$ ). Core-1 is configured with physical interface IP address $10.30.0.2/24$ and Core-2 with $10.30.0.3/24$ . A network administrator enters the configuration command `standby 30 ip 10.30.0.2` on Core-1's VLAN 30 interface. Which outcome occurs when this command is executed?

The router rejects the command because HSRP does not allow the virtual IP address to match an IP address assigned to a physical interface.

The command is accepted, and Core-1 automatically raises its HSRP priority to 255 to become the permanent Active router.

The command is accepted into the running configuration, but Core-1 logs duplicate IP address conflict messages continuously.

The router accepts the command and dynamically derives a virtual MAC address using Core-1's physical burned-in MAC address.

Show answer & explanation

Answer: The router rejects the command because HSRP does not allow the virtual IP address to match an IP address assigned to a physical interface.

Answer

The command is rejected because HSRP virtual IP addresses cannot match any physical interface IP address configured on the router.

Cisco IOS/IOS-XE enforces a fundamental operational rule in HSRP: the virtual IP address must be unique within the subnet and cannot match the physical IP address of any router interface in the HSRP group. Attempting to assign an interface's physical IP address as the HSRP virtual IP results in an immediate CLI error rejecting the command.

Step-by-Step Solution

Analyze the HSRP virtual IP address configuration rule.

In Hot Standby Router Protocol (HSRP v1 and v2), the virtual IP address must be an unused IP address within the subnet assigned to the interface.

Assigning an existing physical interface IP address as the virtual IP would cause internal IP routing conflicts and ARP table ambiguities on the local router.

Compare HSRP behavior with VRRP.

While Virtual Router Redundancy Protocol (VRRP) allows a router to act as the IP address owner by assigning its physical IP address as the virtual IP (setting priority to 255), HSRP explicitly forbids this.

Understanding protocol implementation differences is essential for gateway redundancy administration.

Determine the CLI execution result.

Entering `standby 30 ip 10.30.0.2` on an interface already configured with physical IP

10.30.0.2

causes Cisco IOS to return a command syntax/validation error and reject the entry.

The CLI parser validates the virtual IP against existing interface address configurations immediately upon entry.

Key Concept

HSRP Virtual IP Address Assignment Restrictions

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IP Connectivity

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