IPv4 Static Routing

89 questions

All types89 Multiple choice45 Multiple select21 Ordering23

A network engineer is configuring router R1 to maintain redundant connectivity to an upstream ISP. R1 currently learns a default route ( $0.0.0.0/0$ ) via OSPF, which has a default Administrative Distance of 110. The engineer needs to configure a floating static default route using the next-hop IP address $192.168.12.2$ over a secondary link so that it serves strictly as a backup if the OSPF path fails. Which TWO of the following statements accurately describe the configuration or operational behavior of this floating static route?

Select all that apply

The command `ip route 0.0.0.0 0.0.0.0 192.168.12.2 120` correctly configures the floating static route with an administrative distance higher than OSPF.

The configured floating static route remains in the running configuration but is excluded from the IPv4 routing table while the OSPF default route is active.

The command `ip route 0.0.0.0 0.0.0.0 192.168.12.2 90` creates a valid floating backup static route for the primary OSPF path.

When the primary OSPF link fails, Cisco IOS dynamically alters the administrative distance of the static route from 1 to 120 to activate it.

Show answer & explanation

Answer: The command `ip route 0.0.0.0 0.0.0.0 192.168.12.2 120` correctly configures the floating static route with an administrative distance higher than OSPF.; The configured floating static route remains in the running configuration but is excluded from the IPv4 routing table while the OSPF default route is active.

Answer

The correct statements are that `ip route 0.0.0.0 0.0.0.0 192.168.12.2 120` correctly configures the floating static route, and that the floating static route remains in the running configuration but is excluded from the active IPv4 routing table as long as the primary OSPF default route is active.

A floating static route acts as a backup path and must be configured with an Administrative Distance higher than the primary route protocol (OSPF AD 110). Using `ip route 0.0.0.0 0.0.0.0 192.168.12.2 120` properly assigns an AD of 120. Because Cisco IOS installs only the path with the lowest AD into the routing table, the static route is held in the running configuration and only populated into the IPv4 routing table if the OSPF default route is removed.

Step-by-Step Solution

Identify the Administrative Distance (AD) of the primary dynamic routing protocol

OSPF has a default AD of 110.

Floating static routes rely on having a higher AD than the primary routing method so they are not chosen while the primary route is functional.

Evaluate the required static route syntax and AD parameter

The command `ip route 0.0.0.0 0.0.0.0 192.168.12.2 120` specifies an AD of 120, which is higher than 110.

Setting the AD to 120 satisfies the floating static route requirement.

Determine Cisco IOS routing table insertion rules for floating routes

The static route with AD 120 is stored in configuration but withheld from the routing table while the lower AD OSPF route (AD 110) exists.

The Cisco IOS RIB only installs the route with the lowest AD for a given destination prefix.

Key Concept

Floating Static Routes and Administrative Distance

Question 22Question →

A border router receives a primary IPv4 route for destination network $198.51.100.0/24$ via external BGP (eBGP), which has an administrative distance of $20$ . The network engineer must configure a backup floating static route via next-hop IPv4 address $203.0.113.5$ that remains inactive in the routing table unless the primary eBGP path becomes unavailable. Which command must be configured on the border router to achieve this requirement?

ip route 198.51.100.0 255.255.255.0 203.0.113.5 25

ip route 198.51.100.0 255.255.255.0 203.0.113.5 15

ip route 198.51.100.0 255.255.255.0 203.0.113.5 20

ip route 198.51.100.0 0.0.0.255 203.0.113.5 25

Show answer & explanation

Answer: ip route 198.51.100.0 255.255.255.0 203.0.113.5 25

Answer

The command `ip route 198.51.100.0 255.255.255.0 203.0.113.5 25` correctly configures the backup floating static route.

To configure a floating static route as a backup to an eBGP-learned route (which has a default administrative distance of

20

), the static route must be assigned an administrative distance strictly greater than

20

. Setting the distance to

25

ensures that Cisco IOS places the static route into the routing table only when the eBGP route is withdrawn. Additionally, Cisco IOS static route configuration requires a dotted-decimal subnet mask rather than a wildcard mask.

Step-by-Step Solution

Identify the administrative distance of the primary route protocol.

The primary route is learned via eBGP, which has a default administrative distance of

20

Cisco IOS selects routes with the lowest administrative distance for placement in the routing table.

Determine the required administrative distance for the backup route.

The administrative distance must be set to a value strictly greater than

20

(such as

25

A higher administrative distance keeps the static route floating (inactive) in the background until the primary eBGP path drops.

Verify Cisco IOS IPv4 static route syntax requirements.

The syntax is `ip route <network-prefix> <subnet-mask> <next-hop-ip> [administrative-distance]`.

The command requires a standard subnet mask rather than an OSPF/ACL wildcard mask.

Key Concept

Floating Static Route Administrative Distance Configuration

Estimated Time:1m 30s

Question 23Question →

An engineer is configuring router R1 to reach the internal network $10.50.0.0/16$ using a backup path via next-hop IPv4 address $192.168.12.2$ . The primary route to $10.50.0.0/16$ is currently dynamically learned via EIGRP with an administrative distance of $90$ . Which command must be configured on R1 so that the static route functions as a floating static route and only enters the routing table if the primary route fails?

ip route 10.50.0.0 255.255.0.0 192.168.12.2 95

ip route 10.50.0.0 255.255.0.0 192.168.12.2 80

ip route 10.50.0.0 255.255.0.0 192.168.12.2 90

ip route 10.50.0.0 0.0.255.255 192.168.12.2 95

Show answer & explanation

Answer: ip route 10.50.0.0 255.255.0.0 192.168.12.2 95

Answer

ip route 10.50.0.0 255.255.0.0 192.168.12.2 95

The command 'ip route 10.50.0.0 255.255.0.0 192.168.12.2 95' correctly specifies the target network, subnet mask, next-hop IP address, and an administrative distance of 95. Because 95 is greater than the EIGRP administrative distance of 90, the router will keep this static route out of the routing table until the primary EIGRP route fails.

Step-by-Step Solution

Identify the primary route protocol and its administrative distance.

The primary route is learned via EIGRP, which has an Administrative Distance (AD) of 90.

Floating static routes rely on a higher AD value than the primary path to remain dormant in the routing table.

Determine the required Administrative Distance for the floating static route.

The static route must have an AD greater than 90 (such as 95).

Cisco routers prefer routes with lower AD values; setting the AD higher ensures it is only installed when the primary route disappears.

Verify Cisco IOS static route CLI command syntax.

The format is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip> [administrative-distance]'.

Using dotted-decimal subnet masks and placing the AD at the end of the command line complies with Cisco IOS syntax.

Key Concept

Floating Static Route Administrative Distance Configuration

Estimated Time:1m 0s

Question 24Question →

A network engineer must configure router R1 with a primary static route to reach destination subnet $192.168.20.0/24$ using next-hop IPv4 address $10.1.12.2$ . Additionally, a backup (floating) static route to the same destination subnet must be configured using next-hop IPv4 address $10.1.14.2$ so that it only enters the routing table if the primary path becomes unavailable. Which TWO static route configuration commands must be applied on router R1 to satisfy these requirements? (Select TWO.)

Select all that apply

ip route 192.168.20.0 255.255.255.0 10.1.12.2

ip route 192.168.20.0 255.255.255.0 10.1.14.2 10

ip route 192.168.20.0 255.255.255.0 10.1.14.2 1

ip route 192.168.20.0 255.255.255.0 10.1.12.2 255

Show answer & explanation

Answer: ip route 192.168.20.0 255.255.255.0 10.1.12.2; ip route 192.168.20.0 255.255.255.0 10.1.14.2 10

Answer

The primary path requires the standard command 'ip route 192.168.20.0 255.255.255.0 10.1.12.2' (default AD of 1), while the backup path requires 'ip route 192.168.20.0 255.255.255.0 10.1.14.2 10' with a higher administrative distance.

To create a primary and backup static route relationship, the primary route is configured with the standard static syntax 'ip route 192.168.20.0 255.255.255.0 10.1.12.2', which defaults to an administrative distance of 1. The backup (floating) static route is configured with an administrative distance value strictly greater than the primary route's AD (such as 10) via 'ip route 192.168.20.0 255.255.255.0 10.1.14.2 10'. This ensures the backup route remains inactive until the primary route drops from the routing table.

Step-by-Step Solution

Identify the proper Cisco IOS static route syntax.

The command syntax is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip> [administrative-distance]'.

This establishes reachability to the destination network via a specified next-hop address.

Determine the administrative distance (AD) for the primary static route.

Reaching 192.168.20.0/24 via 10.1.12.2 uses the default static AD of 1.

Static routes without an explicit distance parameter default to an AD of 1.

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

The backup path via 10.1.14.2 requires an AD greater than 1 (such as 10).

A higher AD keeps the route out of the routing table until the lower AD primary route fails.

Key Concept

IPv4 Floating Static Route Configuration and Administrative Distance

Question 25Question →

Router R3 currently populates its routing table with a primary route to the $172.16.40.0/24$ network via OSPF, which carries a default administrative distance of $110$ . A network administrator wants to implement a backup path to $172.16.40.0/24$ using the next-hop IPv4 address $10.2.2.2$ . The backup route must remain inactive in the routing table unless the primary OSPF path becomes unavailable. Which command should be entered on router R3 to accomplish this objective?

ip route 172.16.40.0 255.255.255.0 10.2.2.2 130

ip route 172.16.40.0 255.255.255.0 10.2.2.2 90

ip route 172.16.40.0 0.0.0.255 10.2.2.2 130

ip route 10.2.2.2 255.255.255.0 172.16.40.0 130

Show answer & explanation

Answer: ip route 172.16.40.0 255.255.255.0 10.2.2.2 130

Answer

The command `ip route 172.16.40.0 255.255.255.0 10.2.2.2 130` correctly configures a floating static route with an administrative distance higher than OSPF (110).

A floating static route is an administrative backup route configured with a higher Administrative Distance (AD) than the primary routing protocol. Since OSPF has an AD of

110

, configuring the static route with an AD of

130

ensures it is ignored during normal operation. If the OSPF route disappears from the routing table, the static route with AD

130

takes over forwarding.

Step-by-Step Solution

Identify the destination network, subnet mask, and next-hop IP address.

Destination: 172.16.40.0, Mask: 255.255.255.0, Next-hop IP: 10.2.2.2.

Cisco IOS static route syntax requires `ip route <prefix> <mask> <next-hop|exit-interface> [distance]`.

Determine the administrative distance (AD) of the primary protocol and choose a higher AD for the floating static route.

Primary OSPF AD is 110; the backup route AD must be greater than 110 (e.g., 130).

Routes with lower AD values are preferred. A higher AD ensures the static route remains floating (inactive) until the primary OSPF route fails.

Assemble the complete Cisco IOS CLI command string.

`ip route 172.16.40.0 255.255.255.0 10.2.2.2 130`.

This matches all parameter requirements and syntax rules.

Key Concept

Floating Static Route Administrative Distance Configuration

Estimated Time:1m 15s

Question 26Question →

A Cisco router receives an IPv4 packet destined for $192.168.10.45$ . The router has a single static route configured as follows: `ip route 192.168.10.0 255.255.255.0 10.1.1.2`. Arrange the steps of the router's lookup and packet forwarding process in the correct sequential order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct order of steps for processing a recursive static route lookup is: (1) Receive the IPv4 packet on an ingress interface, (2) Match the destination IP to the static route prefix

192.168.10.0/24

, (3) Identify next-hop IP

10.1.1.2

and initiate a recursive lookup, (4) Resolve the next-hop IP to connected route

10.1.1.0/30

on interface GigabitEthernet0/1, and (5) Encapsulate the packet into a Layer 2 frame and transmit out GigabitEthernet0/1.

When a static route is configured using a next-hop IP address rather than an explicit exit interface (e.g., `ip route 192.168.10.0 255.255.255.0 10.1.1.2`), Cisco IOS performs a recursive lookup process. The router first matches the packet's destination IPv4 address to the static route entry. Next, it extracts the next-hop IP address and performs a second routing table lookup to find which interface connects to that next-hop subnet. Once the exit interface is identified from a connected or secondary route, the router encapsulates the packet in a Layer 2 frame and sends it out the resolved interface.

Step-by-Step Solution

Receive IPv4 packet

Packet destination IP

192.168.10.45

is extracted for table inspection.

Ingress processing triggers the forwarding decision engine.

Match static route prefix

Destination matches `192.168.10.0/24` with next-hop `10.1.1.2`.

Static route entry specifies the destination network reachable via a next-hop IP address.

Perform recursive route lookup

Secondary lookup query initiated for IP address

10.1.1.2

Static routes configured with only a next-hop IP address require a recursive lookup to identify the outgoing physical interface.

Resolve outbound interface

Next-hop

10.1.1.2

resolves to connected interface GigabitEthernet0/1.

The routing table contains a directly connected prefix

10.1.1.0/30

attached to GigabitEthernet0/1.

Encapsulate and forward frame

Packet is sent out GigabitEthernet0/1.

Final packet transmission requires determining the Layer 2 header rewrite details for the specific exit interface.

Key Concept

IPv4 Static Route Recursive Lookup Mechanism

Question 27Question →

A network administrator needs to configure static routes on a Cisco IOS router for destination subnet $10.15.0.0/16$ . The primary route should use next-hop IP address $192.168.1.2$ with default priority. Additionally, a floating static backup route must be configured via next-hop IP address $192.168.2.2$ to take over only if the primary path learned via OSPF (Administrative Distance 110) becomes unavailable. Which two CLI commands correctly configure this static routing behavior? (Select TWO options.)

Select all that apply

ip route 10.15.0.0 255.255.0.0 192.168.1.2

ip route 10.15.0.0 255.255.0.0 192.168.2.2 120

ip route 10.15.0.0 255.255.0.0 192.168.2.2 90

ip route 10.15.0.0 0.0.255.255 192.168.1.2

Show answer & explanation

Answer: ip route 10.15.0.0 255.255.0.0 192.168.1.2; ip route 10.15.0.0 255.255.0.0 192.168.2.2 120

Answer

The correct commands are 'ip route 10.15.0.0 255.255.0.0 192.168.1.2' for the primary static route and 'ip route 10.15.0.0 255.255.0.0 192.168.2.2 120' for the floating static route.

The standard primary static route is configured using subnet mask notation with an implicit administrative distance of 1. To create a floating static route that acts as a backup to OSPF (which has a default administrative distance of 110), the static route must explicitly specify an administrative distance greater than 110, such as 120.

Step-by-Step Solution

Determine the syntax for the primary IPv4 static route.

The command syntax is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip>'. For

10.15.0.0/16

, this is 'ip route 10.15.0.0 255.255.0.0 192.168.1.2'.

Standard static routes use default administrative distance 1.

Determine the administrative distance needed for the floating static backup route.

The backup route must have an administrative distance greater than OSPF (AD = 110), such as 120.

Routes with lower administrative distance are preferred in the routing table. To act as a backup to an OSPF route, the static route AD must exceed 110.

Key Concept

IPv4 Floating Static Route Configuration and Administrative Distance

Estimated Time:1m 30s

Question 28Question →

A Cisco router configured with the static route `ip route 172.16.10.0 255.255.255.0 10.1.1.2` receives an IPv4 packet destined for $172.16.10.45$ . Place the steps performed by the router to process and forward this packet in the correct sequential order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of router operation steps is: (1) Packet arrival at ingress interface, (2) Destination matching against static route prefix 172.16.10.0/24, (3) Extraction of next-hop IP 10.1.1.2, (4) Recursive routing table lookup for 10.1.1.2 to find egress interface, and (5) Layer 2 encapsulation and forwarding out the resolved exit interface.

When a router receives a packet destined for a subnet covered by a next-hop static route, it first matches the destination prefix, identifies the next-hop IP, and then executes a recursive lookup to find the directly connected egress interface before encapsulating and transmitting the frame.

Step-by-Step Solution

Inspect incoming packet destination

Destination IP

172.16.10.45

is identified.

Routing processing begins as soon as a packet enters the router.

Lookup destination in IPv4 routing table

Matches `172.16.10.0/24` pointing to next-hop

10.1.1.2

The router performs a longest prefix match against active routing table entries.

Extract next-hop address requirement

Next-hop IP

10.1.1.2

is identified.

The static route was configured using next-hop IP syntax rather than directly specifying an exit interface.

Execute recursive route resolution lookup

Egress interface (e.g., GigabitEthernet0/1) associated with subnet

10.1.1.0/24

is resolved.

Cisco IOS requires a recursive lookup to resolve next-hop IP addresses to an active, directly connected egress interface.

Encapsulate and forward frame

Packet is framed and transmitted out the egress interface toward

10.1.1.2

Layer 2 headers are constructed after exit interface and next-hop MAC resolution.

Key Concept

Recursive Lookup for Next-Hop IPv4 Static Routes

Question 29Question →

A network engineer needs to configure a backup IPv4 static route on router HQ-Rtr to reach the remote LAN $10.220.50.0/24$ . The primary path to this destination is learned via OSPFv2, which has a default Administrative Distance of 110. The backup static path must be routed through the next-hop IP address $192.168.88.2$ and should only be inserted into the IP routing table if the primary OSPF path fails. Which Cisco IOS command must be configured on HQ-Rtr to achieve this design requirement?

ip route 10.220.50.0 255.255.255.0 192.168.88.2 120

ip route 10.220.50.0 255.255.255.0 192.168.88.2 90

ip route 10.220.50.0 255.255.255.0 192.168.88.2 110

ip route 10.220.50.0 0.0.0.255 192.168.88.2 120

Show answer & explanation

Answer: ip route 10.220.50.0 255.255.255.0 192.168.88.2 120

Answer

The command 'ip route 10.220.50.0 255.255.255.0 192.168.88.2 120' correctly configures a floating static route with an Administrative Distance higher than OSPF.

The command specifying 'ip route 10.220.50.0 255.255.255.0 192.168.88.2 120' uses valid Cisco IOS syntax and assigns an Administrative Distance of 120. Because 120 is higher than OSPF's default Administrative Distance of 110, the static route remains inactive in the routing table until the primary OSPF path is lost.

Step-by-Step Solution

Identify the primary routing protocol and its Administrative Distance (AD).

The primary route is learned via OSPFv2, which has a default AD of 110.

To create a floating (backup) static route, its AD must be higher than the AD of the active primary routing protocol.

Determine the required Administrative Distance for the backup route.

An AD greater than 110 (such as 120) must be specified at the end of the static route command.

Routes with lower AD values are preferred. An AD of 120 ensures the route stays out of the routing table until the primary OSPF route disappears.

Verify Cisco IOS static route syntax.

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

Cisco IOS requires subnet masks in dotted-decimal format (255.255.255.0), not wildcard masks.

Key Concept

Floating Static Route Administrative Distance Selection

Question 30Question →

A network administrator is configuring static routes on router R1 to provide redundancy for destination network $172.20.50.0/24$ . The primary path to this network is currently learned via OSPF with an administrative distance of $110$ . The administrator wants to add a backup static route via next-hop IPv4 address $192.168.12.2$ and evaluate static route forwarding behavior on broadcast networks. Which two statements regarding static route configuration and forwarding logic are correct? (Select two.)

Select all that apply

To function as a backup (floating) static route for the OSPF path, the static route must be configured with an administrative distance value greater than 110.

Configuring the backup static route with an administrative distance of 90 ensures it remains unused until the primary OSPF route goes down.

Configuring an IPv4 static route specifying only an exit interface on a broadcast Ethernet link causes the router to issue ARP requests for destination host IPs, relying on proxy ARP from the next-hop router.

A static route with a /24 prefix length and an administrative distance of 10 will take forwarding precedence over an OSPF route with a /26 prefix length.

Show answer & explanation

Answer: To function as a backup (floating) static route for the OSPF path, the static route must be configured with an administrative distance value greater than 110.; Configuring an IPv4 static route specifying only an exit interface on a broadcast Ethernet link causes the router to issue ARP requests for destination host IPs, relying on proxy ARP from the next-hop router.

Answer

The two correct statements are that a floating static route backing up OSPF must have an administrative distance greater than 110, and that specifying only an exit interface on a broadcast Ethernet link requires proxy ARP on the adjacent router to resolve destination IP addresses.

The statement requiring an administrative distance greater than 110 for a backup route is correct because OSPF has a default AD of 110, so a floating static route must have a higher AD (e.g., 120) to remain inactive until OSPF fails. The statement regarding exit-interface configuration on Ethernet links is also correct because broadcast media require next-hop MAC address resolution, causing the router to send ARP queries for destination IPs which require proxy ARP from the neighboring router.

Step-by-Step Solution

Analyze the floating static route administrative distance requirement.

OSPF has a default administrative distance (AD) of 110. For a static route to serve as a backup (floating static route), its AD must be set higher than 110 (e.g., 120). Setting an AD lower than 110 makes it the preferred active route immediately.

Lower administrative distance values indicate higher route trustworthiness in the Cisco IOS routing table.

Evaluate exit-interface behavior on Ethernet broadcast networks.

When a static route points only to an Ethernet exit interface (without a next-hop IP address), the router considers the destination network directly connected and sends an ARP request for the destination IP address of every traversing packet, relying on the next-hop device to answer via proxy ARP.

Ethernet is a multiaccess media type, so the router cannot automatically determine the next-hop Layer 2 MAC address without an explicit next-hop IP or proxy ARP response.

Verify forwarding precedence rules (Longest Prefix Match vs. AD).

Longest prefix match always takes precedence over administrative distance. A

/26

route is more specific than a

/24

route and will always be chosen for packets matching that subnet, regardless of AD.

Administrative distance is only used to select between routes with identical prefix lengths from different sources when populating the routing table.

Key Concept

IPv4 Static Route Administrative Distance and Next-Hop Resolution Mechanics

Question 31Question →

Router R1 contains the following IPv4 routing table entries for destination networks within the enterprise core:

- A static route to $10.10.4.0/24$ with a configured administrative distance of $110$
- An OSPF route to $10.10.0.0/16$ with an administrative distance of $110$
- A RIP route to $10.10.4.32/27$ with an administrative distance of $120$

When Router R1 receives an IPv4 packet destined for host $10.10.4.50$ , which route will R1 select to forward the traffic?

The RIP route to

10.10.4.32/27

because it has the longest prefix match for the destination address.

The static route to

10.10.4.0/24

because static routes are preferred over dynamic routing protocols when administrative distance is equal.

The OSPF route to

10.10.0.0/16

because OSPF is a link-state protocol with lower overhead than RIP.

Equal-cost load balancing across both the static route and the OSPF route because both have an administrative distance of

110

Show answer & explanation

Answer: The RIP route to $10.10.4.32/27$ because it has the longest prefix match for the destination address.

Answer

Router R1 will select the RIP route to

10.10.4.32/27

because it represents the longest prefix match (27 bits) for the destination host address

10.10.4.50

When a router receives an IP packet, it compares the destination IP address against entries in its routing table. The fundamental rule of IP route selection is Longest Prefix Match (LPM). The destination host

10.10.4.50

matches all three configured routes, but

10.10.4.32/27

has the longest subnet mask prefix length (27 bits vs 24 bits vs 16 bits). Administrative distance is only evaluated when comparing two routes pointing to the exact same prefix and mask length. Therefore, the router forwards traffic using the RIP route despite its higher administrative distance of 120.

Step-by-Step Solution

Convert the destination IP and route prefixes to binary or analyze subnet ranges to find matching routes.

Host

10.10.4.50

falls into all three ranges:

10.10.0.0/16

(range

10.10.0.0

–

10.10.255.255

10.10.4.0/24

(range

10.10.4.0

–

10.10.4.255

), and

10.10.4.32/27

(range

10.10.4.32

–

10.10.4.63

Before comparing administrative distance, the router identifies all routing table entries that match the destination IP address.

Apply Cisco IOS forwarding decision logic rule #1: Longest Prefix Match.

The

/27

mask (27 matching subnet bits) is longer and more specific than

/24

(24 bits) and

/16

(16 bits).

The router always prefers the route with the highest number of matching leading bits, regardless of administrative distance or metric.

Select the forwarding route.

The RIP route to

10.10.4.32/27

is chosen for packet forwarding.

Administrative distance (120 vs 110) is ignored because the prefix lengths are not identical.

Key Concept

Cisco IPv4 Forwarding Decision Logic: Longest Prefix Match Rule

Question 32Question →

A network administrator needs to configure a fully specified IPv4 static route on a Cisco router to reach destination subnet $10.50.0.0/16$ . The next-hop router interface IP address is $172.16.1.2$ , and the outbound multiaccess Ethernet interface on the local router is GigabitEthernet0/0. Which command correctly establishes this route while avoiding recursive routing table lookups?

ip route 10.50.0.0 255.255.0.0 GigabitEthernet0/0 172.16.1.2

ip route 10.50.0.0 0.0.255.255 GigabitEthernet0/0 172.16.1.2

ip route 10.50.0.0 255.255.0.0 172.16.1.2 GigabitEthernet0/0

ip route 10.50.0.0 255.255.0.0 GigabitEthernet0/0 172.16.1.1

Show answer & explanation

Answer: ip route 10.50.0.0 255.255.0.0 GigabitEthernet0/0 172.16.1.2

Answer

The command `ip route 10.50.0.0 255.255.0.0 GigabitEthernet0/0 172.16.1.2` correctly configures a fully specified static route.

A fully specified static route on a broadcast multiaccess interface requires both the local outbound interface name and the next-hop IP address. In Cisco IOS, the command structure is `ip route <prefix> <mask> <exit-interface> <next-hop-ip>`. The option specifying `ip route 10.50.0.0 255.255.0.0 GigabitEthernet0/0 172.16.1.2` adheres strictly to this syntax.

Step-by-Step Solution

Identify the target network address and subnet mask.

Destination prefix is

10.50.0.0

with mask

255.255.0.0

(/16).

Cisco IOS IPv4 static route syntax requires the destination prefix followed by its subnet mask in dotted-decimal format.

Apply Cisco IOS fully specified static route syntax rules.

The correct parameter order after prefix and mask is the exit interface followed by the next-hop IP address.

Specifying both parameters explicitly prevents ARP resolution issues on multiaccess Ethernet segments and eliminates recursive lookup overhead.

Verify parameter placement and values.

Interface GigabitEthernet0/0 precedes next-hop IP

172.16.1.2

The next-hop must belong to the adjacent downstream router, not the local router.

Key Concept

Fully Specified IPv4 Static Route Syntax

Question 33Question →

A Cisco IOS router receives an IPv4 packet destined for $10.150.20.5$ . The routing table contains a static route `ip route 10.150.20.0 255.255.255.0 172.16.1.2` pointing to a next-hop address. Place the steps describing how the router recursively resolves the next-hop and forwards the packet in the correct sequential order from first to last.

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Answer

The correct sequence for recursive next-hop resolution is: receiving the packet and inspecting the destination header, performing the primary routing table lookup for the destination network, executing the recursive lookup for the next-hop IP address, resolving the Layer 2 MAC address on the egress interface, and encapsulating/transmitting the frame.

When a static route is configured with a next-hop IP address rather than a directly connected exit interface, Cisco IOS must perform a recursive lookup. The router first inspects the packet header and matches the destination subnet against the routing table. Next, it identifies the next-hop IP address associated with that static route entry. Because an IP address cannot directly dictate physical egress, a second (recursive) lookup is performed to find which local connected subnet and physical interface reach that next-hop IP. Once GigabitEthernet0/1 is identified, the router checks its ARP table to map the next-hop IP to a destination MAC address, encapsulating and transmitting the frame out the resolved egress interface.

Step-by-Step Solution

Packet Ingress & Parsing

Destination IP

10.150.20.5

is extracted from the IPv4 header.

The router must inspect the destination IP address of an incoming packet to make a forwarding decision.

Primary Routing Lookup

Matches static route

10.150.20.0/24

with next-hop IP

172.16.1.2

The routing table is searched using Longest Prefix Match (LPM) logic.

Recursive Lookup

Resolves next-hop IP

172.16.1.2

to connected interface GigabitEthernet0/1.

When a static route specifies only a next-hop IP address, Cisco IOS requires a secondary lookup to resolve that IP address to a local exit interface.

Layer 2 Address Resolution

ARP table is queried/resolved for next-hop

172.16.1.2

MAC address.

Ethernet interfaces require a destination MAC address to build the Layer 2 frame header.

Frame Encapsulation & Egress

Packet is sent out GigabitEthernet0/1 toward the next-hop router.

The router rewrites the Layer 2 source and destination MAC addresses and pushes the frame out the physical interface.

Key Concept

IPv4 Static Route Recursive Lookup & Packet Forwarding Logic

Question 34Question →

A network administrator needs to configure a backup floating static route on router R1 to reach the internal subnetwork $172.16.50.0/24$ . The primary route to this destination is learned via OSPF, which operates with its default administrative distance. Which command must be configured on R1 so that the static route remains inactive until the primary OSPF path fails?

ip route 172.16.50.0 255.255.255.0 192.168.12.2 120

ip route 172.16.50.0 255.255.255.0 192.168.12.2 110

ip route 172.16.50.0 255.255.255.0 192.168.12.2 90

ip route 172.16.50.0 0.0.0.255 192.168.12.2 120

Show answer & explanation

Answer: ip route 172.16.50.0 255.255.255.0 192.168.12.2 120

Answer

ip route 172.16.50.0 255.255.255.0 192.168.12.2 120

OSPF routes have a default administrative distance of 110. A floating static route acts as a backup path by specifying an administrative distance higher than the primary path (in this case, 120). Cisco IOS uses the format 'ip route destination mask next-hop distance', making 'ip route 172.16.50.0 255.255.255.0 192.168.12.2 120' correct.

Step-by-Step Solution

Determine the administrative distance (AD) of the primary routing protocol

OSPF has a default administrative distance of 110.

Floating static routes rely on administrative distance values to determine path selection priority.

Select an administrative distance value for the backup static route

The backup static route must have an AD greater than 110 (such as 120).

Routers prefer routes with lower administrative distance values. The static route will only be installed into the routing table if the lower-AD OSPF route becomes unavailable.

Verify Cisco IOS static route command syntax

The correct command syntax is 'ip route <destination-prefix> <subnet-mask> <next-hop-ip> [distance]'.

Subnet masks must be entered in standard dotted-decimal format rather than wildcard mask notation.

Key Concept

Floating Static Route Administrative Distance Configuration

Question 35Question →

A network administrator needs to configure a floating static default route on a Cisco IOS router to serve as a backup to an existing OSPF-learned default route (Administrative Distance of 110). Place the operational steps in the correct sequential order to configure, validate normal operation, and verify failover behavior of this backup route.

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Answer

The correct operational sequence begins by analyzing the primary protocol AD (110), navigating to global configuration mode, defining the floating static default route with a higher AD value (120), verifying that the route remains inactive in the routing table during normal operations, and finally testing link failover to confirm RIB insertion.

The workflow follows standard Cisco IOS network administration practices: planning parameters (AD selection), configuration entry, syntax application, baseline verification (confirming inactivity while primary is up), and failover validation (confirming activation when primary drops).

Step-by-Step Solution

Determine the primary route's Administrative Distance.

Identified OSPF AD as 110, requiring a floating static route AD > 110 (e.g., 120).

Floating static routes rely on a higher AD than the active routing source so they remain inactive until the primary route fails.

Access configuration mode.

Router prompt changes to `Router(config)#`.

Cisco IOS static route creation requires global configuration access.

Apply the static route configuration.

Configured `ip route 0.0.0.0 0.0.0.0 203.0.113.2 120`.

Defines a default route (`0.0.0.0 0.0.0.0`) pointing to next-hop `203.0.113.2` with an AD argument of `120`.

Verify initial routing table state.

Confirmed OSPF route is active in RIB and static route is absent.

Ensures the floating route does not preempt the primary dynamic path while the primary path is healthy.

Test path failover under fault conditions.

Static route `S* 0.0.0.0/0 [120/0] via 203.0.113.2` appears in `show ip route` output upon primary interface shutdown.

Validates proper failover functionality when the primary route is removed from the routing table.

Key Concept

Floating Static Route Lifecycle and Failover Validation

Estimated Time:2m 0s

Question 36Question →

An engineer is configuring a backup link on router R2 to reach the internal network $10.50.0.0/16$ . The primary path is currently learned dynamically via OSPF, which has a default administrative distance of 110. Which Cisco IOS command correctly configures a floating static route that remains inactive unless the primary OSPF route fails?

ip route 10.50.0.0 255.255.0.0 172.16.12.2 120

ip route 10.50.0.0 255.255.0.0 172.16.12.2 90

ip route 10.50.0.0 255.255.0.0 172.16.12.2 110

ip route 10.50.0.0 0.0.255.255 172.16.12.2 120

Show answer & explanation

Answer: ip route 10.50.0.0 255.255.0.0 172.16.12.2 120

Answer

The command 'ip route 10.50.0.0 255.255.0.0 172.16.12.2 120' correctly configures the floating static route.

A floating static route acts as a secondary path that is installed into the routing table only when the primary path fails. To achieve this behavior, the static route must be configured with an Administrative Distance (AD) higher than that of the primary routing protocol. Since OSPF has a default AD of 110, setting the static route AD to 120 ensures it stays in reserve.

Step-by-Step Solution

Identify the primary route's Administrative Distance (AD)

OSPF has a default AD of 110.

Floating static routes must have an AD strictly greater than the primary route's AD to remain hidden in the routing table until the primary path drops.

Verify Cisco IOS IPv4 static routing syntax

The correct format is 'ip route <destination-network> <subnet-mask> <next-hop-ip> [distance]'.

Standard subnet masks (dotted-decimal) are mandatory in Cisco IOS static routing syntax.

Select the option with an AD greater than 110 and proper subnet mask syntax

The command specifying an AD of 120 with mask 255.255.0.0 meets both requirements.

An AD of 120 ensures the static route is kept in backup state while OSPF is active.

Key Concept

Floating Static Route Administrative Distance Selection

Question 37Question →

A network administrator needs to manually configure a floating static route on a Cisco IOS router to serve as a backup path. Arrange the required command components in the correct sequential order from left to right as typed in the CLI.

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Answer

The correct sequence for configuring a floating IPv4 static route in Cisco IOS is: `ip route` keyword, destination network address, subnet mask, next-hop IPv4 address (or exit interface), and administrative distance.

The standard Cisco IOS syntax for configuring an IPv4 static route is `ip route <destination-prefix> <subnet-mask> {ip-address | exit-interface} [distance]`. Placing `ip route` first, followed by the destination network prefix, subnet mask, next-hop IP address, and finally the administrative distance creates a valid floating static route.

Step-by-Step Solution

Identify the global configuration command mode keyword

Start with `ip route`.

Cisco IOS requires the keyword `ip route` to initiate an IPv4 static route entry.

Specify target destination network parameters

Provide the destination network IP (`192.168.20.0`) followed by its subnet mask (`255.255.255.0`).

The router must know which destination address block this route applies to.

Define forwarding path

Specify the next-hop IP address (`10.1.1.2`) or local exit interface.

The router requires explicit instructions on where to send matching packets.

Configure administrative distance for backup behavior

Append an administrative distance value greater than the primary protocol's AD (e.g., `130`).

Setting an AD higher than the primary route (such as OSPF AD 110) ensures the static route remains floating until the primary fails.

Key Concept

Cisco IOS IPv4 Static Route Command Syntax and Floating Route Configuration

Question 38Question →

A network engineer is analyzing the forwarding behavior of router R1 for traffic destined to IP address $172.20.16.45$ . The router currently has an active OSPFv2 process that learns prefix $172.20.16.0/20$ (Administrative Distance 110). Additionally, the administrator configures three IPv4 static routes on R1:

- Command 1: `ip route 172.20.16.0 255.255.240.0 10.0.0.2 115`
- Command 2: `ip route 172.20.16.0 255.255.255.0 10.0.1.2`
- Command 3: `ip route 172.20.16.32 255.255.255.224 10.0.2.2 120`

Assuming all next-hop IP addresses ( $10.0.0.2$ , $10.0.1.2$ , and $10.0.2.2$ ) are reachable via directly connected subnets, which route will router R1 use to forward the packet destined to $172.20.16.45$ , and why?

The static route from Command 3 via next-hop 10.0.2.2, because it is installed in the routing table and has the longest prefix match (/27) for the destination IP address.

The static route from Command 2 via next-hop 10.0.1.2, because it has the lowest Administrative Distance (1) among all valid static routes matching the destination.

The OSPF dynamic route via next-hop 10.0.0.2, because Command 1 and Command 3 both have Administrative Distances higher than OSPF (110) and are ignored.

The static route from Command 1 via next-hop 10.0.0.2, because static routes always take precedence over dynamic protocols regardless of prefix length or Administrative Distance.

Show answer & explanation

Answer: The static route from Command 3 via next-hop 10.0.2.2, because it is installed in the routing table and has the longest prefix match (/27) for the destination IP address.

Answer

The router forwards the packet via the static route from Command 3 (next-hop 10.0.2.2) because it is installed in the routing table and provides the longest prefix match (/27) for IP address 172.20.16.45.

The correct answer identifies that the static route configured in Command 3 via next-hop 10.0.2.2 is installed in the routing table and selected via the Longest Prefix Match rule. AD comparison only suppresses a route when another protocol offers the exact same destination prefix and mask with a lower AD. Because Command 3 specifies 172.20.16.32/27, no exact match conflict exists with OSPF (172.20.16.0/20) or Command 2 (172.20.16.0/24), allowing Command 3 into the routing table. When forwarding a packet to 172.20.16.45, the router evaluates all installed routes matching the IP address and picks /27 as the longest prefix match.

Step-by-Step Solution

Evaluate Routing Information Base (RIB) installation for each static route based on Administrative Distance (AD).

Command 1 (172.20.16.0/20, AD 115) matches OSPF prefix 172.20.16.0/20 (AD 110). Because OSPF AD < 115, Command 1 is not installed (floating static route). Command 2 (172.20.16.0/24, default AD 1) and Command 3 (172.20.16.32/27, AD 120) have unique prefixes, so AD comparison against OSPF does not prevent their installation.

Administrative Distance is only compared between routes with identical prefix and subnet mask definitions.

Determine which installed RIB entries match destination IP 172.20.16.45.

Matching installed routes: OSPF (172.20.16.0/20), Command 2 static route (172.20.16.0/24), and Command 3 static route (172.20.16.32/27).

172.20.16.45 falls within the host ranges of all three installed subnets: /20 (172.20.16.0 - 172.20.31.255), /24 (172.20.16.0 - 172.20.16.255), and /27 (172.20.16.32 - 172.20.16.63).

Apply router forwarding decision logic to select the active path for the packet.

Select 172.20.16.32/27 via next-hop 10.0.2.2.

Routers select paths based on the Longest Prefix Match (LPM) rule. A /27 prefix (27 mask bits) is longer and more specific than /24 or /20.

Key Concept

Routing Table Installation (AD Comparison for Exact Matches) vs Packet Forwarding Logic (Longest Prefix Match)

Question 39Question →

A network engineer is optimizing IPv4 static routing on a Cisco IOS router connected to multiple broadcast Ethernet segments. The router currently learns internal prefix 10.10.10.0/24 via OSPFv2 (Administrative Distance 110). Which TWO statements accurately describe the forwarding and configuration behavior of static routes applied to this router? (Select two.)

Select all that apply

Configuring 'ip route 10.10.10.0 255.255.255.0 GigabitEthernet0/1 120' creates a floating static route relative to OSPF, but specifying only an Ethernet exit interface forces the router to rely on Proxy ARP from the next-hop device to resolve destination MAC addresses.

Traffic destined to 10.10.10.130 will be forwarded via next-hop 192.168.13.2 when both 'ip route 10.10.10.0 255.255.255.0 192.168.12.2' (AD 1) and 'ip route 10.10.10.128 255.255.255.192 192.168.13.2 130' are in the routing table, because longest prefix match evaluation precedes Administrative Distance comparison.

The command 'ip route 10.10.10.0 255.255.255.0 192.168.12.2 90' functions as a floating static backup route that remains inactive in the routing table until the primary OSPF route (AD 110) fails.

Configuring a static default route with 'ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0' on a multi-access Ethernet interface eliminates recursive routing lookups while preventing unnecessary ARP table bloat.

Show answer & explanation

Answer: Configuring 'ip route 10.10.10.0 255.255.255.0 GigabitEthernet0/1 120' creates a floating static route relative to OSPF, but specifying only an Ethernet exit interface forces the router to rely on Proxy ARP from the next-hop device to resolve destination MAC addresses.; Traffic destined to 10.10.10.130 will be forwarded via next-hop 192.168.13.2 when both 'ip route 10.10.10.0 255.255.255.0 192.168.12.2' (AD 1) and 'ip route 10.10.10.128 255.255.255.192 192.168.13.2 130' are in the routing table, because longest prefix match evaluation precedes Administrative Distance comparison.

Answer

The correct options are the statement regarding Proxy ARP dependency when using an Ethernet exit interface for a floating static route with Administrative Distance 120, and the statement confirming that longest prefix match (/26 over /24) dictates path selection over Administrative Distance during packet forwarding.

The option describing a floating static route with AD 120 is correct because floating backup routes must have a higher AD than the primary protocol (OSPF = 110), and specifying an Ethernet interface without a next-hop IP requires Proxy ARP to discover destination MAC addresses. The option addressing destination 10.10.10.130 is also correct because the router prioritizes the most specific prefix match (/26 over /24) during forwarding lookup regardless of the AD of the installed static routes.

Step-by-Step Solution

Evaluate floating static route behavior and exit interface considerations.

OSPF has a default AD of 110. A static route configured with AD 120 has a higher distance, floating out of the routing table until OSPF fails. On broadcast Ethernet interfaces, omitting the next-hop IP forces ARP queries for individual target IPs, requiring Proxy ARP on adjacent devices.

Floating routes require AD > primary protocol AD. Broadcast interfaces need explicit next-hop IPs to prevent per-destination ARP lookups.

Analyze routing decision hierarchy (Longest Prefix Match vs Administrative Distance).

Administrative distance determines which routes are installed into the routing table. Once installed, packet forwarding decisions rely strictly on the Longest Prefix Match (/26 mask matches 10.10.10.130 more specifically than /24).

Prefix length (/26 > /24) takes absolute priority during active packet forwarding lookup.

Identify misconceptions in backup static route AD configuration and default route exit interface usage.

Configuring AD 90 makes the static route primary over OSPF (AD 110), failing the floating backup requirement. Pointing a static route (or default route) solely to an Ethernet exit interface causes severe ARP table expansion.

Lower AD wins installation; broadcast interfaces treat all destinations as local when no next-hop IP is provided.

Key Concept

IPv4 Static Route Selection, Administrative Distance, and Exit Interface Dynamics

Estimated Time:3m 0s

Question 40Question →

A network administrator needs to manually configure a backup floating static route on a Cisco IOS router. Arrange the following syntax elements in the correct sequential order from left to right to construct a valid Cisco IOS floating static route command.

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Answer

The correct sequence to construct the command is: ip route 172.16.1.0 255.255.255.0 10.1.1.2 130.

The correct order follows the standard Cisco IOS static route syntax: 'ip route <destination-prefix> <subnet-mask> {ip-address | exit-interface} [distance]'. The command starts with 'ip route', followed by the target destination network (172.16.1.0), the subnet mask (255.255.255.0), the next-hop address (10.1.1.2), and finally the optional Administrative Distance value (130).

Step-by-Step Solution

Begin with the global configuration command keyword.

Specifies 'ip route' at the beginning of the command string.

Cisco IOS requires the 'ip route' command keyword to define a static routing entry.

Append the destination network address followed by its subnet mask.

Adds '172.16.1.0 255.255.255.0'.

The router needs the target IP subnet prefix and corresponding subnet mask to evaluate match length in the routing table.

Specify the next-hop IP address or local exit interface.

Adds '10.1.1.2'.

Defines the forwarding destination or gateway to reach the target network.

Append the optional Administrative Distance value at the end.

Adds '130'.

Assigning an Administrative Distance higher than the primary route (e.g., OSPF AD 110) creates a floating static route that remains inactive until the primary route drops.

Key Concept

Cisco IOS IPv4 static route CLI syntax structure and floating static route parameter placement.

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