IPv4 Static Routing

89 questions

Question 41Question

An enterprise edge router receives internal routing updates for the prefix 192.168.50.0/24192.168.50.0/24 via OSPFv2 (Administrative Distance 110) and iBGP (Administrative Distance 200). A network administrator intends to provision a floating static route via next-hop 10.0.12.210.0.12.2 that remains inactive during normal operation, activates as a backup if the OSPF path fails, and takes precedence over the iBGP path. The administrator executes the following Cisco IOS command:

`ip route 192.168.50.0 255.255.255.0 10.0.12.2 105`

What is the operational result of this configuration, and what modification is required to achieve the desired routing behavior?

Show answer & explanation

Answer: The static route immediately replaces the OSPF route in the routing table because its Administrative Distance of 105 is lower than 110; the Administrative Distance must be reconfigured to a value between 111 and 199.

Answer

The static route immediately overrides the OSPF path because an Administrative Distance of 105 is lower than OSPF's default distance of 110. To function as a floating static backup for OSPF while remaining preferred over iBGP, the Administrative Distance must be configured to a value strictly between 111 and 199.
Cisco IOS selects routes for installation in the routing table based on Administrative Distance (AD), where lower values represent higher trustworthiness. OSPFv2 has a default AD of 110 and iBGP has a default AD of 200. Configuring the static route with AD 105 makes it more trustworthy than OSPF (105<110105 < 110), causing it to immediately active in the routing table rather than functioning as a backup. To properly float behind OSPF but remain ahead of iBGP, its AD must be set within the range of 111 to 199 (such as 120).

Step-by-Step Solution

1
Analyze the Administrative Distance (AD) hierarchy of the active protocols and proposed static route.
Primary path: OSPFv2 (AD 110). Secondary requirement: Floating static backup. Tertiary path: iBGP (AD 200). Configured static route AD: 105.
Administrative Distance determines route trustworthiness in the Cisco IOS Routing Table. Lower AD values are preferred.
2
Evaluate the effect of configuring AD 105 on the router.
Since 105<110105 < 110, the static route overrides OSPF immediately and enters the routing table as the active route, breaking its intended role as a backup route.
A floating static route must have an AD higher than the primary route protocol so that it remains inactive until the primary route drops.
3
Determine the valid AD range for the floating static route.
The AD value XX must satisfy 110<X<200110 < X < 200 (e.g., X=120X = 120).
This guarantees that OSPF (110) is preferred when available, the static route (XX) activates when OSPF fails, and iBGP (200) is used only as a last resort.

Key Concept

Floating Static Route Administrative Distance Calibration
Estimated Time:2m 0s
Question 42Question

A router receives routes for the destination network 10.20.0.0/16 dynamically from OSPF, which uses a default administrative distance of 110. A network administrator needs to create a backup static route for this network using the next-hop address 192.168.1.2 so that it only becomes active if the primary OSPF path fails. Which Cisco IOS command correctly configures this floating static route?

Show answer & explanation

Answer: ip route 10.20.0.0 255.255.0.0 192.168.1.2 120

Answer

The command 'ip route 10.20.0.0 255.255.0.0 192.168.1.2 120' correctly configures the floating static route.
The correct command uses standard Cisco IOS syntax with destination network 10.20.0.0, subnet mask 255.255.0.0 for /16, next-hop address 192.168.1.2, and an administrative distance of 120. Because 120 is greater than OSPF's default AD of 110, the static route remains inactive in the routing table until the primary OSPF route fails.

Step-by-Step Solution

1
Identify the required static route components in Cisco IOS syntax
Syntax format: ip route <destination-network> <subnet-mask> <next-hop-ip> [administrative-distance]
Cisco IOS requires exact keyword ordering and standard dotted-decimal subnet masks.
2
Convert the /16 prefix length to a dotted-decimal subnet mask
/16 equals 255.255.0.0
IPv4 static routing commands require a subnet mask, not a wildcard mask.
3
Determine the required Administrative Distance (AD) for a floating static route
The AD must be higher than the primary routing protocol's AD (OSPF = 110), so an AD of 120 is chosen
Floating static routes are kept out of the routing table until the primary route with a lower AD becomes unavailable.

Key Concept

Floating static route configuration requires an administrative distance higher than the primary dynamic routing protocol.
Question 43Question

A Cisco IOS router (R1) is configured with three routes for the destination prefix 192.168.10.0/24192.168.10.0/24: a primary static route (`ip route 192.168.10.0 255.255.255.0 10.0.12.2`), an active OSPFv2 dynamic route (Administrative Distance 110 via 10.0.14.210.0.14.2), and a backup floating static route (`ip route 192.168.10.0 255.255.255.0 10.0.13.2 120`). Place the control plane and data plane events in the correct chronological sequence starting immediately after the physical interface connected to 10.0.12.210.0.12.2 fails.

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Answer

The correct sequence of events is: Interface link failure → Primary static route RIB withdrawal → AD evaluation selecting OSPF over floating static → FIB table update → Forwarding of packets via the OSPF path.
When an active egress interface fails, Cisco IOS immediately removes the connected static route from the Routing Information Base (RIB). The router then re-evaluates all available candidate routes for the exact destination prefix (192.168.10.0/24192.168.10.0/24). Because the prefix lengths are identical, the router compares Administrative Distance (AD). OSPF (AD 110) is preferred over the floating static route (AD 120). Once the RIB settles on the OSPF path, the control plane programs the Forwarding Information Base (FIB), and data plane traffic resumes forwarding out the OSPF next-hop.

Step-by-Step Solution

1
Identify link status change
Interface going down invalidates directly associated static route next-hops.
Cisco IOS requires an active interface to keep static routes active in the RIB.
2
Withdraw primary static route from RIB
Primary static route with Administrative Distance 1 is purged.
Unreachable next-hop interfaces trigger route removal.
3
Compare Administrative Distance of remaining matching prefixes
OSPF route (AD 110) is selected instead of the floating static route (AD 120).
When prefix lengths match exactly (192.168.10.0/24192.168.10.0/24), the route with the lowest Administrative Distance is installed.
4
Update Cisco Express Forwarding (CEF) FIB hardware tables
FIB updates pointer for 192.168.10.0/24192.168.10.0/24 to point to 10.0.14.210.0.14.2.
RIB modifications must sync to the FIB for hardware-accelerated forwarding.
5
Process data plane traffic
Packets targeting 192.168.10.50192.168.10.50 switch path to 10.0.14.210.0.14.2.
Subsequent ingress traffic matches the newly installed FIB lookup entry.

Key Concept

IPv4 Static Route RIB Lifecycle, Floating Static Administrative Distance Calibration, and CEF FIB Convergence
Question 44Question

An administrator is implementing a floating static route on a Cisco IOS router to act as a backup path for a primary route learned dynamically via internal EIGRP (Administrative Distance 90) to the destination subnet 10.100.50.0/2410.100.50.0/24. The administrator executes the following command:

`ip route 10.100.50.0 255.255.255.0 172.16.1.2 90`

While the primary EIGRP route remains active, traffic destined for 10.100.50.0/2410.100.50.0/24 is unexpectedly load-shared across both the dynamic route and the static route. Which configuration change will ensure that the static route functions exclusively as a backup route?

Show answer & explanation

Answer: Reconfigure the static route with an administrative distance greater than 90.

Answer

Reconfigure the static route with an administrative distance greater than 90.
For a static route to act as a floating backup route, its administrative distance must be configured higher than the administrative distance of the primary route. Since internal EIGRP uses an AD of 90, configuring the static route with an AD of 90 causes both routes to share the same administrative distance, resulting in unexpected dual-path active insertion. Assigning an AD greater than 90 keeps the static route out of the routing table until the primary EIGRP route fails.

Step-by-Step Solution

1
Analyze the administrative distance of the primary routing protocol.
Internal EIGRP has a default administrative distance of 90.
Administrative distance determines route preference in the Cisco IOS Routing Information Base (RIB).
2
Evaluate the current static route configuration.
The configured static route explicitly sets an administrative distance of 90, matching EIGRP's administrative distance.
When two routes to the exact same prefix have equal administrative distances, the router treats them as equally trustworthy, leading to unexpected traffic load-sharing or tie-breaking behavior.
3
Determine the requirement for a floating static route.
A floating static route must have an administrative distance strictly higher than the primary route's AD (e.g., 91 or 130).
This guarantees the static route remains inactive in the RIB until the primary dynamic route is removed.

Key Concept

Floating Static Route Administrative Distance Calibration
Question 45Question

An enterprise router R1 learns the internal destination network 10.50.0.0/1610.50.0.0/16 dynamically via OSPF (default Administrative Distance of 110). A network administrator needs to manually configure two IPv4 static routes on R1:
1. A secondary backup (floating) static route to reach 10.50.0.0/1610.50.0.0/16 via the next-hop IP address 192.168.12.2192.168.12.2.
2. A default static route to forward all non-matching IPv4 traffic to the upstream ISP router at next-hop IP 203.0.113.1203.0.113.1.

Which TWO commands must be configured on router R1 to achieve these routing requirements? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: ip route 10.50.0.0 255.255.0.0 192.168.12.2 130; ip route 0.0.0.0 0.0.0.0 203.0.113.1

Answer

The correct commands are 'ip route 10.50.0.0 255.255.0.0 192.168.12.2 130' to establish a floating static route with an Administrative Distance higher than OSPF (110), and 'ip route 0.0.0.0 0.0.0.0 203.0.113.1' to establish a standard default static route using the prefix 0.0.0.0/0.
To create a floating static route, the Administrative Distance specified at the end of the 'ip route' command must be higher than that of the primary routing source. Since OSPF has an AD of 110, setting an AD of 130 guarantees the route will only be installed in the Routing Information Base (RIB) if the primary OSPF route disappears. Additionally, a default static route requires matching any IP address, configured with destination network 0.0.0.0 and subnet mask 0.0.0.0 pointing to the next-hop router address.

Step-by-Step Solution

1
Determine the primary route's Administrative Distance (AD) for network 10.50.0.0/16.
OSPF has a default AD of 110.
Floating static routes must have an AD strictly greater than the active dynamic protocol's AD to remain inactive until primary route failure.
2
Validate the floating static route syntax and AD parameter.
The command syntax 'ip route 10.50.0.0 255.255.0.0 192.168.12.2 130' specifies an AD of 130, which is higher than 110.
AD 130 ensures the static route remains floating in backup mode until OSPF drops the path.
3
Formulate the default static route syntax for all unrouted traffic.
A default route uses destination prefix 0.0.0.0 and subnet mask 0.0.0.0 followed by the next-hop IP 203.0.113.1.
The prefix 0.0.0.0 0.0.0.0 matches any IPv4 address with a 0-bit prefix length.

Key Concept

Floating Static Routes and Default Static Route Syntax
Question 46Question

A network engineer wants to configure a floating static route to serve as a backup to a primary route learned via OSPF, which has an Administrative Distance of 110. Which Administrative Distance value should be specified in the static route command so that it is only installed in the routing table when the OSPF route fails?

Show answer & explanation

Answer: 120

Answer

The correct administrative distance is 120 because a floating static route must have an administrative distance higher than the primary routing protocol (OSPF AD 110) to remain inactive until the primary route fails.
A floating static route acts as a backup route and is configured with an Administrative Distance higher than that of the primary routing protocol. Since OSPF has an AD of 110, setting the static route's AD to 120 keeps it out of the routing table until the primary OSPF route becomes unavailable.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary routing protocol.
The primary route is learned via OSPF, which has a default AD of 110.
Administrative Distance determines route trustworthiness, where a lower AD value is preferred.
2
Determine the required AD relationship for a floating (backup) static route.
The floating static route must be configured with an AD strictly greater than 110.
If the static route has a lower or equal AD, it will be preferred over or compete with the primary OSPF route.
3
Select the valid option that satisfies the backup requirement.
An AD of 120 is greater than 110 and represents standard backup static routing behavior.
120 is higher than 110, ensuring the route stays in floating status until the OSPF route fails.

Key Concept

Floating Static Route Administrative Distance Configuration
Question 47Question

A Cisco router receives an IPv4 packet destined for host 192.168.10.45192.168.10.45, which matches a static route configured strictly with a next-hop IP address (10.0.0.210.0.0.2) rather than an exit interface. Arrange the operational steps in the exact sequence the router executes to process, resolve, and forward this packet.

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Answer

The correct sequence of router operation steps is: Extract the destination IPv4 address (192.168.10.45192.168.10.45), search the IPv4 RIB using Longest Prefix Match, identify the next-hop IPv4 address (10.0.0.210.0.0.2), perform a recursive lookup to resolve the exit interface, and consult the ARP table to encapsulate and transmit the packet.
When a Cisco router receives an IPv4 packet, it extracts the destination IP address from the packet header (192.168.10.45192.168.10.45). Next, it evaluates its routing table (RIB) using Longest Prefix Match (LPM) to find the most specific route entry. Upon finding the static route, it identifies that the destination is reached via next-hop IP 10.0.0.210.0.0.2. Because the static route was configured without specifying an egress interface, the router must perform a recursive lookup in the routing table to determine which directly connected interface reaches 10.0.0.210.0.0.2. Once the exit interface is resolved, the router queries its ARP cache to map 10.0.0.210.0.0.2 to a Layer 2 MAC address, re-encapsulates the packet into a new Layer 2 frame, and transmits it out the interface.

Step-by-Step Solution

1
Packet Ingress and Header Parsing
Destination IPv4 address 192.168.10.45192.168.10.45 is extracted.
The router needs the destination IPv4 address to perform a routing lookup.
2
RIB Query via Longest Prefix Match
The static route entry best matching 192.168.10.45192.168.10.45 is selected.
Routing decisions in Cisco IOS prioritize routes with the longest prefix length.
3
Next-Hop Extraction
Next-hop IPv4 address 10.0.0.210.0.0.2 is retrieved from the static route entry.
The router identifies that the traffic must be sent to 10.0.0.210.0.0.2 before reaching the final destination.
4
Recursive Route Resolution
Next-hop 10.0.0.210.0.0.2 is resolved to a directly connected exit interface.
Static routes configured solely with next-hop IP addresses require a second routing lookup to identify the physical outbound interface.
5
Layer 2 Resolution & Encapsulation
ARP table maps 10.0.0.210.0.0.2 to its destination MAC address, the packet is encapsulated into a Layer 2 frame, and forwarded.
The router must encapsulate the IP packet into a valid Ethernet frame using the exit interface and next-hop MAC address.

Key Concept

Recursive Static Route Lookup and Packet Forwarding Sequence
Question 48Question

Router R1 connects an enterprise edge network to two service providers, ISP-A and ISP-B. The primary default path is dynamically learned from ISP-A via eBGP, which assigns an Administrative Distance (AD) of 2020. A network engineer needs to configure a floating static default route toward ISP-B through next-hop IP 198.51.100.1198.51.100.1 as a redundant backup path that will remain inactive in the routing table until the primary eBGP path fails. Which Cisco IOS command correctly achieves this objective?

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Answer: ip route 0.0.0.0 0.0.0.0 198.51.100.1 25

Answer

The command 'ip route 0.0.0.0 0.0.0.0 198.51.100.1 25' correctly specifies a default route with an Administrative Distance higher than the primary eBGP AD of 20, ensuring it remains inactive until link failure.
A floating static route acts as a backup path and must remain inactive in the Routing Information Base (RIB) until the primary route fails. Because the primary route is dynamically learned via eBGP with an Administrative Distance (AD) of 20, the static backup route must be explicitly configured with an AD value strictly greater than 20. The option specifying 'ip route 0.0.0.0 0.0.0.0 198.51.100.1 25' correctly applies an AD of 25 to the default network 0.0.0.0/0, ensuring it functions strictly as a backup.

Step-by-Step Solution

1
Identify the primary route source and its administrative distance.
Primary default route is learned via eBGP, which has an Administrative Distance of 2020.
Floating static routes must be assigned an Administrative Distance higher than the primary protocol's AD.
2
Determine the correct IPv4 default static route prefix and mask syntax.
Default route destination is represented as '0.0.0.0 0.0.0.0'.
A quad-zero prefix and mask match any destination network not explicitly matched by more specific routes.
3
Select the appropriate Administrative Distance for the backup floating route.
Specify an Administrative Distance greater than 2020 (e.g., 2525).
Setting the AD to 2525 keeps the static route hidden from the Routing Information Base (RIB) while the primary eBGP route (AD 2020) is active.

Key Concept

Floating Static Route Administrative Distance Selection
Question 49Question

A network administrator needs to configure reliable static default routing on a Cisco IOS router by tying a primary static route to an IP SLA probes object, ensuring that the route is automatically withdrawn if the target becomes unreachable. Arrange the operational and CLI configuration steps in the correct chronological order from establishing the probe metric to static route activation.

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Answer

The correct chronological sequence is: (1) Define and schedule the IP SLA probe instance, (2) Create the object tracking process monitoring IP SLA reachability, (3) Configure the static route bound to the track object ID, and (4) Verify probe success leading to tracking state UP and RIB installation.
The correct sequence follows the mandatory dependency hierarchy in Cisco IOS: first, the IP SLA engine must be defined and scheduled to generate active probes; second, a tracking object must be constructed to translate probe results into a boolean UP/DOWN status; third, the IPv4 static route must be configured with the `track` keyword; and finally, once the tracking object confirms reachability (UP state), the router installs the static route into the routing table (RIB).

Step-by-Step Solution

1
Configure and schedule the IP SLA ICMP Echo probe operation.
The router begins sending ICMP echo packets to target IP 203.0.113.1203.0.113.1.
Tracking objects require an active underlying probe instance to supply reachability status.
2
Bind the IP SLA operation to a tracking object ID using `track <id> ip sla <ops-number> reachability`.
Tracking object status changes to UP when SLA probe responses are received successfully.
Static routes cannot monitor IP SLA probes directly; they must reference a tracking object.
3
Apply the `ip route` global configuration command specifying the next-hop IP and the `track <id>` parameter.
The static route is created in conditional status linked to tracking object state.
Adding the `track` keyword instructs Cisco IOS to conditionally evaluate RIB placement.
4
Cisco IOS processes the UP status of the tracking object and writes the route to the routing table.
The default static route becomes active in the RIB with Administrative Distance 11.
RIB installation occurs only when the tracked object returns a valid UP reachability state.

Key Concept

IPv4 Static Route Object Tracking with IP SLA
Question 50Question

A branch router receives an external EIGRP route (EIGRP EX, Administrative Distance of 170) for the corporate subnet 10.200.0.0/1610.200.0.0/16 over a primary MPLS link. A network administrator must configure a floating static backup route for 10.200.0.0/1610.200.0.0/16 using the secondary ISP next-hop address 192.168.1.2192.168.1.2. The backup path must only be installed in the IPv4 routing table if the primary EIGRP EX path becomes unavailable. Which command must be configured on the router to achieve this requirement?

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Answer: ip route 10.200.0.0 255.255.0.0 192.168.1.2 175

Answer

The command 'ip route 10.200.0.0 255.255.0.0 192.168.1.2 175' correctly configures the floating static route.
A floating static route acts as a backup path and must have an Administrative Distance (AD) strictly higher than the primary route currently in use. Because External EIGRP routes have a default AD of 170, the backup static route must be configured with an AD greater than 170 (such as 175). Furthermore, Cisco IOS static route syntax requires the destination network mask to be specified as a standard subnet mask (255.255.0.0) rather than a wildcard mask.

Step-by-Step Solution

1
Identify the primary route's Administrative Distance (AD).
External EIGRP (EIGRP EX) routes have a default Administrative Distance of 170.
Floating static routes must have an AD higher than the primary route's AD to remain inactive in the routing table until failure occurs.
2
Determine the required Administrative Distance for the floating static route.
The static route AD must be strictly greater than 170 (e.g., 175).
Cisco IOS selects routes with lower AD values first. A higher AD keeps the route out of the routing table while the primary path is active.
3
Verify Cisco IOS IPv4 static route syntax requirements.
The proper command structure is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip> [distance]'.
Static IPv4 routing in Cisco IOS requires a standard dotted-decimal subnet mask (255.255.0.0 for /16), not an OSPF/ACL wildcard mask.

Key Concept

Floating static route configuration requiring higher Administrative Distance than dynamic primary routes
Question 51Question

An enterprise edge router dynamically learns the network prefix 10.50.40.0/24 from an internal switch via Internal EIGRP (Administrative Distance 90). A network administrator needs to configure a floating static backup route for this prefix using the next-hop IPv4 address 192.168.254.2 across a secondary connection. Which Cisco IOS command correctly configures the floating static route so that it remains inactive in the routing table until the primary EIGRP path fails?

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Answer: ip route 10.50.40.0 255.255.255.0 192.168.254.2 95

Answer

ip route 10.50.40.0 255.255.255.0 192.168.254.2 95
The correct option uses standard subnet mask notation (255.255.255.0) and specifies an administrative distance of 95. Because 95 is higher than Internal EIGRP's administrative distance of 90, the router retains this static route as an inactive backup and installs it into the IPv4 routing table only if the EIGRP path becomes unavailable.

Step-by-Step Solution

1
Determine the administrative distance of the primary route.
Internal EIGRP has a default administrative distance of 90.
Floating static routes must have an administrative distance strictly greater than the active primary routing protocol to stay hidden from the routing table during normal operation.
2
Evaluate Cisco IOS IPv4 static route syntax requirements.
The command syntax requires 'ip route <prefix> <mask> <next-hop-ip> [administrative-distance]'.
Subnet masks must be written in standard dotted-decimal notation (e.g., 255.255.255.0) rather than inverse wildcard notation.
3
Select the option with valid CLI syntax and an administrative distance higher than 90.
The command setting an administrative distance of 95 satisfies all criteria.
An administrative distance of 95 ensures the static route remains floating until the primary EIGRP route with AD 90 is withdrawn.

Key Concept

Floating Static Route Administrative Distance Selection
Question 52Question

A Cisco IOS router receives an IPv4 packet destined for host 192.168.2.45192.168.2.45. The router's routing table contains a static route configured as `ip route 192.168.2.0 255.255.255.0 10.1.1.2`. Place the processing steps the router executes to resolve the exit interface and encapsulate the packet in the correct sequential order from first to last.

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Answer

The correct sequential order for recursive static route lookup and forwarding is: 1) Match destination IP against the routing table to select the static route; 2) Identify next-hop IP address 10.1.1.2; 3) Perform a recursive lookup in the routing table for 10.1.1.2; 4) Match the connected route 10.1.1.0/24 to determine exit interface GigabitEthernet0/1; 5) Retrieve the ARP table entry for 10.1.1.2 to encapsulate and transmit the frame.
When a static route is configured using only a next-hop IP address (e.g., `ip route 192.168.2.0 255.255.255.0 10.1.1.2`), Cisco IOS must execute a recursive lookup process. The router first matches the packet destination IP (192.168.2.45192.168.2.45) against the static route in the routing table. Second, it identifies the configured next-hop IP (10.1.1.210.1.1.2). Third, it performs a secondary (recursive) lookup for 10.1.1.210.1.1.2 in the routing table. Fourth, it finds the directly connected route (10.1.1.0/2410.1.1.0/24), revealing the physical egress interface (GigabitEthernet0/1). Fifth, it queries the ARP table for the MAC address belonging to 10.1.1.210.1.1.2 to build the Ethernet frame and transmit it out GigabitEthernet0/1.

Step-by-Step Solution

1
Evaluate the incoming packet's destination IPv4 address.
The router matches host destination 192.168.2.45192.168.2.45 to static prefix 192.168.2.0/24192.168.2.0/24.
Routing decisions start by determining the longest matching prefix for the destination IP address.
2
Inspect forwarding parameters specified in the matched static route entry.
The router determines that the route specifies next-hop IP address 10.1.1.210.1.1.2.
Static routes configured strictly with a next-hop IP address do not directly name an exit interface.
3
Execute a recursive lookup for IP address 10.1.1.210.1.1.2.
The router searches the RIB for a route covering 10.1.1.210.1.1.2.
Recursive resolution is mandatory when a next-hop IP is used without an explicit exit interface specification.
4
Resolve the next-hop IP to a connected network route.
The router matches 10.1.1.210.1.1.2 to connected network 10.1.1.0/2410.1.1.0/24 on interface GigabitEthernet0/1.
The connected route provides the physical exit interface necessary to transmit the traffic.
5
Query the ARP table and perform Layer 2 frame encapsulation.
The destination MAC address associated with 10.1.1.210.1.1.2 is acquired and the frame is transmitted via GigabitEthernet0/1.
Multi-access Ethernet media require resolving the next-hop IPv4 address to its target MAC address before physical transmission.

Key Concept

Recursive Routing Lookup for IPv4 Static Routes
Question 53Question

Router R1 learns the primary route to destination network 10.50.0.0/1610.50.0.0/16 via OSPF, which has a default Administrative Distance of 110. A network engineer must configure a static backup route to the same network that remains inactive in the routing table until the OSPF route fails. Which Administrative Distance value must be assigned to the static route?

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Answer: 120

Answer

120
A floating static route functions as a backup path by configuring its Administrative Distance (AD) to be higher than the AD of the primary routing protocol. Since OSPF has an AD of 110, setting the static route's AD to 120 ensures it is kept out of the routing table until the primary OSPF route becomes unavailable.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary dynamic routing protocol.
OSPF has a primary AD of 110.
Cisco IOS selects routes based on lower Administrative Distance values when multiple paths to the same destination exist.
2
Determine the required AD relationship for a floating static backup route.
The static route AD must be strictly greater than 110.
A floating static route must have a higher AD than the primary route so it remains hidden until the primary route disappears.
3
Select the option with an AD greater than 110.
120 is greater than 110.
Using an AD of 120 keeps the static route out of the routing table during normal operation.

Key Concept

Floating Static Route Administrative Distance Configuration
Estimated Time:45s
Question 54Question

An enterprise router R1 learns an internal EIGRP route to the destination network 10.50.40.0/2410.50.40.0/24 with an Administrative Distance of 90. A network administrator attempts to configure a floating static backup route for this target subnet via next-hop address 192.168.12.2192.168.12.2 by issuing the command `ip route 10.50.40.0 255.255.255.0 192.168.12.2 85`. Which statement accurately describes the operational impact of this configuration on router R1?

Show answer & explanation

Answer: The static route immediately replaces the primary EIGRP route in the active routing table because its configured Administrative Distance of 85 is lower than EIGRP's Administrative Distance of 90.

Answer

The static route pre-empts the primary EIGRP route and becomes the primary active route in the routing table because its configured Administrative Distance of 85 is lower than internal EIGRP's Administrative Distance of 90.
In Cisco IOS routing, when multiple routing sources provide a path to the exact same prefix, the router installs the route with the lowest Administrative Distance (AD). Internal EIGRP has a default AD of 90. By setting the static route's AD to 85, the static route is considered more trustworthy than EIGRP and immediately pre-empts the EIGRP route in the routing table.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary dynamic protocol.
Internal EIGRP has a default AD of 90.
Administrative Distance represents trustworthiness; lower values are preferred.
2
Analyze the configured static route parameter.
The command specifies an explicit AD metric of 85 (`ip route 10.50.40.0 255.255.255.0 192.168.12.2 85`).
The final optional integer argument in an `ip route` command sets the custom AD value.
3
Compare the AD values of both sources for the exact same destination prefix.
Static AD (85) < EIGRP AD (90).
To create a floating static route (backup), the configured AD MUST be higher than the primary route's AD (e.g., > 90). Setting it lower causes the static route to pre-empt the primary dynamic route.

Key Concept

Floating Static Route Administrative Distance Selection
Question 55Question

An administrator needs to manually configure an IPv4 static route on a Cisco router to reach remote network 172.20.10.0/24172.20.10.0/24 using the next-hop IP address 10.0.0.210.0.0.2, and then permanently save the configuration. What is the correct sequence of steps to complete this configuration starting from Privileged EXEC mode?

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Answer

The correct order to enter global configuration mode, apply the static route command with the correct prefix, subnet mask, and next-hop IP, exit back to privileged EXEC mode, and save the active configuration to NVRAM is: Enter global configuration mode (`configure terminal`), Configure the static route (`ip route 172.20.10.0 255.255.255.0 10.0.0.2`), Return to privileged EXEC mode (`end`), and Save the configuration (`copy running-config startup-config`).
Configuring a persistent IPv4 static route on a Cisco router requires moving to global configuration mode via `configure terminal`, applying the static route with `ip route 172.20.10.0 255.255.255.0 10.0.0.2`, exiting back to privileged EXEC mode using `end`, and finally writing the running configuration to NVRAM using `copy running-config startup-config`.

Step-by-Step Solution

1
Transition from Privileged EXEC mode (`Router#`) to Global Configuration mode (`Router(config)#`).
The router prompt changes to `Router(config)#`, allowing structural configuration commands.
Static routes cannot be defined directly in Privileged EXEC mode.
2
Issue the IPv4 static route command `ip route 172.20.10.0 255.255.255.0 10.0.0.2`.
The static route is added to the running configuration and installed into the IPv4 routing table.
Cisco IOS requires the syntax `ip route <prefix> <mask> <next-hop-ip|exit-interface>`.
3
Return to Privileged EXEC mode using `end` or `exit`.
The prompt reverts back to `Router#`.
File management and memory write commands must be issued from Privileged EXEC mode.
4
Write the active configuration from RAM to NVRAM using `copy running-config startup-config`.
The current running-config is saved to startup-config in NVRAM.
Without saving, configuration modifications will be lost if the device loses power or reboots.

Key Concept

Cisco IOS IPv4 Static Route CLI Configuration Workflow
Question 56Question

A network administrator intends to configure a floating static route on Router R1 to serve as a backup to a primary route dynamically learned via OSPF (Administrative Distance 110) for destination network 172.16.50.0/24172.16.50.0/24. However, while the primary OSPF link remains healthy and operational, the administrator observes that the newly added static route immediately overrides the OSPF route in the IPv4 routing table. Which command did the administrator incorrectly execute on Router R1?

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Answer: ip route 172.16.50.0 255.255.255.0 192.168.1.2 90

Answer

The command 'ip route 172.16.50.0 255.255.255.0 192.168.1.2 90' was incorrectly configured because assigning an Administrative Distance lower than 110 causes the static route to immediately preempt the primary OSPF path.
In Cisco IOS, static routes have a default Administrative Distance (AD) of 1. A floating static route acts as a backup path and must be configured with an AD higher than the primary route's protocol AD. Because OSPF has a default AD of 110, setting the static route's AD to 90 gives it higher priority (lower AD number) than OSPF. Consequently, the router immediately installs the static route into the routing table and ignores the active OSPF route.

Step-by-Step Solution

1
Analyze the requirement for a floating static route.
A floating static route must have an Administrative Distance (AD) higher than the primary routing protocol so that it remains inactive in the routing table until the primary route fails.
Cisco IOS routing logic selects paths based on the lowest Administrative Distance first.
2
Compare the AD of the primary route (OSPF) against the attempted static route.
OSPF has a default AD of 110. To act as a backup, the static route AD must be greater than 110 (such as 120).
If the static route is configured with an AD lower than 110 (such as 90), the router prefers the static route over the OSPF route.
3
Identify which misconfiguration caused the immediate routing table override.
The command specifying an AD of 90 is preferred over OSPF's AD of 110, causing immediate installation into the routing table.
Lower AD numbers indicate higher trustworthiness in Cisco IOS.

Key Concept

Floating Static Route Administrative Distance Selection
Question 57Question

A network engineer is configuring IPv4 static routes on a Cisco IOS router. Which TWO statements accurately describe the characteristics and syntax of Cisco IPv4 static routing? (Select two.)

Select all that apply

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Answer: A floating static route must be configured with an administrative distance higher than the administrative distance of the primary route.; Static routes configured pointing directly to a point-to-point exit interface do not require a recursive lookup to resolve the next-hop IP address.

Answer

The two correct statements state that a floating static route requires an administrative distance higher than the primary route, and that static routes pointing to a point-to-point exit interface bypass recursive lookup.
Floating static routes rely on having a higher administrative distance than the primary route so they stay out of the routing table until the primary route fails. Additionally, specifying a point-to-point exit interface allows direct frame transmission without a recursive next-hop lookup.

Step-by-Step Solution

1
Evaluate the administrative distance requirement for floating static routes.
Floating static routes are designed as backup routes. Routers prefer lower administrative distance (AD) values. Therefore, a floating static route must have a higher AD than the primary route to remain inactive until the primary route fails.
Lower AD indicates higher trustworthiness in Cisco IOS forwarding decisions.
2
Analyze how next-hop resolution works with point-to-point exit interfaces.
Specifying a point-to-point exit interface resolves the egress interface immediately without needing a second (recursive) lookup for a next-hop IP address.
Point-to-point links have only one destination on the link, so the router knows directly where to send frames.
3
Verify incorrect distractor statements.
Setting an AD of 10 for a backup to EIGRP (AD 90) makes the static route active immediately, overriding EIGRP instead of floating behind it. Additionally, static route syntax uses subnet masks, not wildcard masks.
Wildcard masks are syntax elements of ACLs/OSPF, not Cisco IOS 'ip route' commands.

Key Concept

IPv4 Static Route Syntax and Floating Static Route Principles
Question 58Question

An administrator is configuring a backup floating static route on a Cisco router for destination network 10.50.0.0/1610.50.0.0/16. The primary path to this network is currently learned via EIGRP with an administrative distance of 90. Which `ip route` command correctly implements a backup static route via next-hop IP 192.168.100.2192.168.100.2 that takes effect only if the primary EIGRP route fails?

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Answer: ip route 10.50.0.0 255.255.0.0 192.168.100.2 95

Answer

The command 'ip route 10.50.0.0 255.255.0.0 192.168.100.2 95' correctly configures a floating static route by specifying a higher Administrative Distance (95) than EIGRP (90).
The correct option uses valid Cisco IOS static route syntax with a standard subnet mask (255.255.0.0) and assigns an administrative distance of 95. Because 95 is higher than the primary EIGRP path AD of 90, the route remains inactive in the routing table until the primary EIGRP path becomes unavailable.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary dynamic routing protocol
EIGRP internal routes have a default Administrative Distance of 90.
Floating static routes must have an AD higher than the primary route's AD to remain inactive until the primary route fails.
2
Verify standard Cisco IOS IPv4 static routing CLI syntax
The correct format is 'ip route <destination-network> <subnet-mask> <next-hop-ip> [administrative-distance]'.
IPv4 static routes require dotted-decimal subnet masks rather than wildcard masks.
3
Select the command with a valid subnet mask and an AD greater than 90
An AD of 95 ensures the static route is floating and only populated in the routing table when the EIGRP route is withdrawn.
An AD of 95 is strictly greater than 90 and less than the default static route AD of 1 or backup limits.

Key Concept

Floating Static Route Administrative Distance Selection
Question 59Question

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.

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Answer

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.

Step-by-Step Solution

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.

Key Concept

Cisco IOS CLI hierarchy navigation and static route command syntax
Question 60Question

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.

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Answer

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.

Step-by-Step Solution

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.

Key Concept

IPv4 Static Route Recursive Lookup & Packet Forwarding Logic
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