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IPv4 Static Routing

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Question 61Question →

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

Select all that apply

Show answer & explanation

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

Answer

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

Step-by-Step Solution

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

Key Concept

IPv4 Static Route Forwarding & Syntax Characteristics
Estimated Time:1m 0s
Question 62Question →

An enterprise edge router R1 connects to two distinct Internet Service Providers via Ethernet interfaces. The network team requires primary outbound traffic to traverse ISP-1 via next-hop IPv4 address 203.0.113.1/30203.0.113.1/30 on interface GigabitEthernet0/0/1. A backup path must traverse ISP-2 via next-hop IPv4 address 198.51.100.1/30198.51.100.1/30 on interface GigabitEthernet0/0/2, taking effect only if the primary route fails.

Which two configuration statements or operational characteristics are correct for implementing this routing strategy?

Select all that apply

Show answer & explanation

Answer: Configuring `ip route 0.0.0.0 0.0.0.0 203.0.113.1` creates the primary default route with an implicit Administrative Distance of 11.; Configuring `ip route 0.0.0.0 0.0.0.0 198.51.100.1 130` establishes a floating static route that remains inactive in the routing table while the primary route is reachable.

Answer

The primary default static route is configured with `ip route 0.0.0.0 0.0.0.0 203.0.113.1` using the default Administrative Distance of 1, while the backup default route is configured with `ip route 0.0.0.0 0.0.0.0 198.51.100.1 130` with a higher Administrative Distance to serve as a floating backup.
The command defining the primary static route uses the standard `ip route 0.0.0.0 0.0.0.0 <next-hop>` syntax, which automatically assigns a default Administrative Distance of 1. The command setting the floating static backup specifies an Administrative Distance of 130, which is higher than the primary route's AD of 1, ensuring it is installed in the active forwarding table only when the primary path becomes unreachable.

Step-by-Step Solution

1
Analyze primary route configuration syntax and Administrative Distance default values.
The command `ip route 0.0.0.0 0.0.0.0 203.0.113.1` creates a default static route pointing to next-hop 203.0.113.1203.0.113.1. By default, IPv4 static routes have an Administrative Distance of 11.
Default static routes require an administrative distance lower than backup routes to be installed in the routing table first.
2
Evaluate requirements for a floating static route.
A floating static route must have its Administrative Distance manually configured to a value higher than the primary route (e.g., 130>1130 > 1).
Cisco IOS selects routes with the lowest Administrative Distance. Higher AD static routes remain in the running configuration but are hidden from the active IP routing table until the primary route drops.
3
Examine errors in alternative configuration choices.
Using an AD of 11 for the secondary route results in equal-cost routes rather than a backup. Specifying only an Ethernet exit interface without a next-hop IP forces the router to perform ARP requests for every internet destination address, requiring Proxy ARP on the ISP peer.
Ethernet is a multiaccess medium; without a next-hop IPv4 address specified, destination IP-to-MAC resolution relies on Proxy ARP.

Key Concept

IPv4 Default and Floating Static Route Configuration Mechanics
Question 63Question →

A network administrator executes the command `ip route 10.50.1.0 255.255.255.0 172.16.1.2 120` on a Cisco IOS router. What does the numeric value `120` at the end of this command represent?

Show answer & explanation

Answer: The administrative distance configured for the static route

Answer

The administrative distance configured for the static route
In Cisco IOS software, the standard syntax for configuring a static route is `ip route <prefix> <mask> {ip-address | exit-interface} [distance]`. When an optional integer value such as 120 is included at the end, it defines the administrative distance (AD) of the static route, overriding the default static route AD of 1.

Step-by-Step Solution

1
Analyze the Cisco IOS IPv4 static route syntax structure.
The standard syntax is `ip route <destination-prefix> <subnet-mask> {ip-address | exit-interface} [distance]`.
Identifying parameter placement clarifies the function of each element in the CLI command.
2
Evaluate the role of the trailing optional parameter.
The numeric value `120` occupies the `[distance]` argument position.
An optional integer specified after the next-hop IP or exit interface sets the administrative distance, commonly used to create a floating static route.

Key Concept

Cisco IOS IPv4 static route command syntax and Administrative Distance configuration
Question 64Question →

A Cisco router receives an IPv4 packet destined for a remote subnet. Place the operational steps performed by the router to evaluate IPv4 static routes and forward the packet into the correct sequential order from first to last.

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Answer

The correct sequence of operations is: (1) Extract and inspect the destination IPv4 address from the incoming packet header, (2) Search the routing table for matching static routes and identify the candidate entry with the longest prefix match, (3) Evaluate Administrative Distance if multiple static routes exist for the identical network prefix, and (4) Encapsulate the packet into a Layer 2 frame and transmit it out the resolved exit interface toward the next hop.
When an IPv4 packet arrives on a Cisco router interface, the router inspects the destination IP address in the packet header. It then searches the routing table to find all matching network prefixes, selecting the entry with the longest prefix match (most specific mask). If there are multiple static routes configured for the exact same prefix length, the router breaks the tie by choosing the route with the lowest Administrative Distance. Finally, the router determines the exit interface/next-hop IP, rewrites the Layer 2 frame, and transmits the packet.

Step-by-Step Solution

1
Packet Ingress & Header Inspection
The destination IPv4 address is read from the packet.
The router requires the target destination address to perform a routing table lookup.
2
Longest Prefix Match Selection
The routing table entry with the longest subnet mask matching the destination IP is selected.
Cisco IOS router forwarding logic prioritizes the most specific prefix match over less specific routes.
3
Administrative Distance Tie-Breaking
If multiple static routes exist for the exact same prefix, the route with the lowest Administrative Distance is used.
Administrative Distance ranks route believability when multiple routes exist for identical destination prefixes.
4
Layer 2 Encapsulation and Forwarding
The packet is encapsulated into the outbound Layer 2 frame format and sent out the exit interface.
Final forwarding requires rewriting Layer 2 headers for the outbound physical or logical link.

Key Concept

IPv4 Static Route Lookup and Forwarding Decision Logic
Question 65Question →

A Cisco router receives an IPv4 packet destined for host 192.168.50.45192.168.50.45. The router's routing table contains a static route `ip route 192.168.50.0 255.255.255.0 10.1.1.2` and a directly connected network 10.1.1.0/3010.1.1.0/30 out interface `GigabitEthernet0/1`. Arrange the sequential processing steps executed by the router to forward this packet from initial ingress lookup to egress transmission.

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Answer

The correct sequence is: Extract the destination IP address -> Perform primary routing lookup -> Perform recursive lookup for the next-hop IP -> Query ARP table for next-hop MAC -> Encapsulate packet and transmit out egress interface.
When a Cisco router receives an IP packet, it first extracts the destination IP address. Using longest prefix match, it matches the static route entry pointing to next-hop IP 10.1.1.2. Because this route specifies an IP next-hop rather than an outbound interface directly, the router performs a recursive lookup to find which connected interface reaches 10.1.1.2 (GigabitEthernet0/1). Knowing the egress Ethernet interface, it resolves the next-hop MAC address using ARP, encapsulates the IPv4 packet in an Ethernet frame, and transmits it out GigabitEthernet0/1.

Step-by-Step Solution

1
Inspect destination header
Destination IPv4 address 192.168.50.45192.168.50.45 is extracted from the incoming frame.
Routing decisions are based on the packet's destination IPv4 address.
2
Execute primary route table lookup
Matches route `192.168.50.0 255.255.255.0` with next-hop IP 10.1.1.210.1.1.2.
The router uses longest prefix matching to select the route entry.
3
Execute recursive lookup
Resolves 10.1.1.210.1.1.2 to directly connected route 10.1.1.0/3010.1.1.0/30 on interface `GigabitEthernet0/1`.
Static routes configured solely with a next-hop IP address require a recursive lookup to identify the exit interface.
4
Resolve Layer 2 next-hop address
Obtains the target MAC address for 10.1.1.210.1.1.2 from the ARP table.
Ethernet encapsulation requires a destination Layer 2 MAC address for the next hop.
5
Encapsulate and egress
Frame is sent out `GigabitEthernet0/1`.
Final physical delivery step out the egress interface.

Key Concept

IPv4 Static Route Recursive Lookup & Packet Forwarding Pipeline
Estimated Time:2m 0s
Question 66Question →

A network administrator is evaluating the IPv4 static routing configuration on router R1. Router R1 needs to reach the remote subnet 10.80.16.0/2010.80.16.0/20. The primary routing path to this destination is currently provided by OSPF, which has an administrative distance of 110. The administrator must configure two static routes:

1. A static route using next-hop IPv4 address 172.16.30.2172.16.30.2 that immediately takes precedence over the OSPF route.
2. A floating static route using next-hop IPv4 address 172.16.40.2172.16.40.2 that serves as a backup only if the OSPF route becomes unavailable.

Which TWO static route commands must be configured on router R1 to achieve this objective? (Select TWO.)

Select all that apply

Show answer & explanation

Answer: ip route 10.80.16.0 255.255.240.0 172.16.30.2; ip route 10.80.16.0 255.255.240.0 172.16.40.2 120

Answer

The correct commands are 'ip route 10.80.16.0 255.255.240.0 172.16.30.2' for the primary route and 'ip route 10.80.16.0 255.255.240.0 172.16.40.2 120' for the floating static backup route.
To create a primary static route that overrides OSPF (AD 110), the standard command 'ip route 10.80.16.0 255.255.240.0 172.16.30.2' uses the default administrative distance of 1, which is lower than 110 and thus preferred. To configure a floating static backup route for the same subnet via next-hop 172.16.40.2, the command 'ip route 10.80.16.0 255.255.240.0 172.16.40.2 120' assigns an administrative distance of 120, which is higher than OSPF's 110, ensuring it only enters the routing table if the OSPF route drops.

Step-by-Step Solution

1
Convert prefix length /20 to dotted-decimal subnet mask format.
A /20 prefix corresponds to a subnet mask of 255.255.240.0.
Cisco IOS static route syntax requires the destination network mask in dotted-decimal format rather than CIDR notation.
2
Determine the required Administrative Distance (AD) for the primary static route.
Use the default static route AD of 1 (or any value lower than OSPF's AD of 110).
Lower administrative distance values are preferred in the Cisco routing table forwarding decision logic.
3
Determine the required Administrative Distance (AD) for the backup floating static route.
Configure an AD greater than 110 (such as 120) for the next-hop 172.16.40.2.
A floating static route must have a higher AD than the primary dynamic routing protocol (OSPF = 110) so it is installed in the routing table only when the primary path goes down.

Key Concept

Cisco IOS IPv4 static route syntax and floating static route administrative distance selection.
Question 67Question →

Router Edge-1 is connected to a primary service provider using external BGP (eBGP, Administrative Distance 20) and a secondary service provider using an IPv4 static route to reach destination network 192.168.100.0/24192.168.100.0/24. The network engineer intends for the static route to serve strictly as a floating backup path that only activates if the primary eBGP route fails. During a routing table audit, the engineer discovers that the static route is active in the routing table even while the primary eBGP link is fully operational.

The current static route configuration on Edge-1 is:
`ip route 192.168.100.0 255.255.255.0 10.0.12.2 15`

Which configuration change on router Edge-1 will ensure that the static route functions correctly as a backup path?

Show answer & explanation

Answer: Reconfigure the static route as `ip route 192.168.100.0 255.255.255.0 10.0.12.2 25` so its administrative distance exceeds that of eBGP.

Answer

Reconfigure the static route as `ip route 192.168.100.0 255.255.255.0 10.0.12.2 25` so its administrative distance exceeds that of eBGP.
A floating static route serves as a backup path and must have an Administrative Distance (AD) configured higher than that of the primary route source. Since eBGP routes have a default AD of 20, setting the static route's AD to 25 ensures it will only be installed into the routing table if the primary eBGP route fails.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary routing protocol.
eBGP has a default Administrative Distance of 20.
Administrative Distance measures route trustworthiness; lower AD values are preferred by the routing table.
2
Analyze why the current static route is active in the routing table.
The current static route has an explicit AD of 15, which is lower than eBGP (20).
Because 15 < 20, the router selects the static route as the primary path instead of treating it as a backup.
3
Determine the AD requirement for a floating static route.
The static route's AD must be set to a value strictly greater than 20 (e.g., 25).
Setting the AD higher than the primary routing protocol ensures the static route remains inactive in the RIB until the primary eBGP route is withdrawn.

Key Concept

Floating Static Route Administrative Distance Calibration
Estimated Time:2m 0s
Question 68Question →

A network administrator is configuring a backup floating static route on router R1 to reach the internal subnet 10.20.0.0/1610.20.0.0/16. The primary path to this destination is currently learned dynamically via OSPF, which has a default Administrative Distance of 110110. The backup route should traverse next-hop IPv4 address 192.168.12.2192.168.12.2 and must enter the routing table only when the primary OSPF path becomes unavailable. Which Cisco IOS command correctly achieves this objective?

Show answer & explanation

Answer: ip route 10.20.0.0 255.255.0.0 192.168.12.2 120

Answer

The correct command is 'ip route 10.20.0.0 255.255.0.0 192.168.12.2 120'.
A floating static route is configured by specifying an administrative distance higher than that of the primary routing protocol. Since OSPF has an Administrative Distance of 110, setting an AD of 120 ensures the static route remains untracked in the routing table during normal operation and only activates if the primary OSPF route drops out.

Step-by-Step Solution

1
Determine the destination prefix and subnet mask for 10.20.0.0/16.
Destination prefix is 10.20.0.0 and the 16-bit subnet mask in dotted-decimal format is 255.255.0.0.
Cisco IOS static route syntax uses subnet masks rather than wildcard masks.
2
Identify the next-hop IP address.
Next-hop IP address is 192.168.12.2.
The scenario explicitly designates 192.168.12.2 as the exit path for backup traffic.
3
Select an Administrative Distance (AD) greater than the primary route's AD.
OSPF default AD is 110; therefore, the floating static route requires an AD greater than 110 (such as 120).
Routers prefer lower Administrative Distance values. Assigning a value higher than 110 ensures the static route remains inactive in the routing table until OSPF fails.

Key Concept

Floating Static Routes and Administrative Distance
Question 69Question →

A network administrator is configuring a backup floating static route on router R3 to reach the remote destination network 192.168.50.0/24. The primary path to this network is dynamically learned via EIGRP with a default administrative distance of 90. The secondary path should route traffic through the next-hop IPv4 address 10.1.1.2.

Which TWO statements regarding this floating static route configuration are correct?

Select all that apply

Show answer & explanation

Answer: The command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` correctly configures the backup route.; The floating static route will be installed into the active IPv4 routing table only when the primary EIGRP route is removed.

Answer

The correct choices are using the command `ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` and recognizing that the route is installed into the routing table only when the primary EIGRP route is removed.
To create a floating static route that backs up an EIGRP path (AD 90), the static route must be configured with an administrative distance greater than 90. The command specifying an AD of 100 correctly accomplishes this. As a result, the router holds the static route in reserve and only installs it into the active IPv4 routing table if the primary EIGRP route is withdrawn.

Step-by-Step Solution

1
Identify the primary route's Administrative Distance (AD).
The primary path is learned via internal EIGRP, which has a default administrative distance of 90.
Floating static routes depend on AD ranking to remain inactive until the primary routing source drops.
2
Determine the required AD value for the floating static route.
The AD configured for the static route must be strictly greater than 90 (e.g., 100).
Cisco routers select routes with lower AD values for insertion into the active IPv4 routing table.
3
Evaluate the command syntax and routing behavior.
`ip route 192.168.50.0 255.255.255.0 10.1.1.2 100` correctly assigns an AD of 100, ensuring the route stays dormant while EIGRP is active.
If the static route AD is set lower than 90 (such as 80), it preempts EIGRP and improperly acts as the primary path.

Key Concept

Floating Static Route Administrative Distance Selection
Question 70Question →

A network engineer is configuring an IPv4 static route on router HQ to reach the destination subnet 172.16.40.0/24172.16.40.0/24. Router HQ connects to the next-hop router over an Ethernet broadcast multi-access segment via interface GigabitEthernet0/1. The engineer enters the command `ip route 172.16.40.0 255.255.255.0 GigabitEthernet0/1` without specifying the next-hop IP address. Which operational issue will occur on router HQ as a result of configuring only the exit interface on a multi-access link?

Show answer & explanation

Answer: The router treats the destination network as directly connected and sends an ARP request for every destination IP address in the 172.16.40.0/24 subnet, causing ARP table bloat and performance degradation.

Answer

The router treats the destination network as directly connected and sends an ARP request for every destination IP address in the 172.16.40.0/24 subnet, causing ARP table bloat and performance degradation.
Specifying only an exit interface on a broadcast multi-access link (like Ethernet) causes the router to treat the remote prefix as directly connected. When forwarding traffic, the router issues an ARP request for every individual destination IP within that prefix. This relies heavily on proxy ARP from the next-hop router, causing unnecessary ARP broadcast traffic and consuming significant Memory/CPU resources due to ARP cache growth.

Step-by-Step Solution

1
Analyze static route exit interface behavior on broadcast networks.
When a static route specifies only a multi-access exit interface (such as Ethernet), Cisco IOS assumes the destination network resides directly on that interface segment.
Directly connected interface routes prompt the router to attempt Layer 2 MAC address resolution for every individual target destination IP address.
2
Evaluate layer 2 address resolution mechanics (ARP).
Router HQ generates an ARP request broadcast for each unique IP address in the 172.16.40.0/24172.16.40.0/24 network.
Without a explicit next-hop IP specified in the route, the router relies on proxy ARP from the neighboring router, creating large ARP tables and high broadcast overhead.

Key Concept

Directly Attached Static Routes on Multi-Access Ethernet Links
Estimated Time:1m 30s
Question 71Question →

A network administrator is configuring IPv4 static routes on router R1. The administrator must implement a primary default static route pointing to next-hop IP address 203.0.113.1203.0.113.1, as well as a backup floating static route for destination subnet 172.16.10.0/24172.16.10.0/24 via next-hop IP 192.168.1.2192.168.1.2. The backup route must take effect only if the primary path learned via OSPF (Administrative Distance of 110) becomes unavailable. Which two commands must the administrator execute on router R1 to satisfy these requirements? (Select two.)

Select all that apply

Show answer & explanation

Answer: ip route 0.0.0.0 0.0.0.0 203.0.113.1; ip route 172.16.10.0 255.255.255.0 192.168.1.2 120

Answer

The administrator must configure the default route using `ip route 0.0.0.0 0.0.0.0 203.0.113.1` and the floating static backup route using `ip route 172.16.10.0 255.255.255.0 192.168.1.2 120`.
The default route requires the prefix and mask `0.0.0.0 0.0.0.0` pointing to next-hop 203.0.113.1203.0.113.1. To serve as a backup to an OSPF route with an Administrative Distance of 110, the floating static route must specify an Administrative Distance higher than 110, which the command specifying an AD of 120 accomplishes.

Step-by-Step Solution

1
Determine the standard command syntax for an IPv4 default static route.
A default route matches all destination networks using prefix 0.0.0.00.0.0.0 and mask 0.0.0.00.0.0.0, forming the command `ip route 0.0.0.0 0.0.0.0 203.0.113.1`.
Quad-zero notation (0.0.0.0 0.0.0.0) is required in Cisco IOS to represent any unlisted IPv4 destination.
2
Calculate the necessary Administrative Distance for a floating static route intended to back up OSPF.
OSPF has a default Administrative Distance of 110. The backup static route requires an Administrative Distance higher than 110 (such as 120).
Cisco routers select routes based on the lowest Administrative Distance. A higher AD keeps the static route inactive until the primary OSPF route is removed from the routing table.

Key Concept

IPv4 Default Static Route Syntax and Floating Static Route Administrative Distance Selection
Question 72Question →

A network engineer observes that traffic from a branch office router toward destination network 172.22.0.0/16172.22.0.0/16 is taking a low-speed backup WAN link instead of the primary OSPF path. Reviewing the running configuration reveals the following static route entry configured for the backup link:

`ip route 172.22.0.0 255.255.0.0 10.0.99.2 105`

Which statement correctly explains why the backup static route is overriding the primary OSPF path?

Show answer & explanation

Answer: The configured administrative distance of 105 is lower than the default administrative distance of OSPF (110), causing the router to prefer the static route.

Answer

The configured administrative distance of 105 is lower than the default administrative distance of OSPF (110), causing the router to prefer the static route.
Administrative distance measures route source believability on Cisco routers, where lower values are preferred. OSPF routes have a default administrative distance of 110. Because the static route was configured with an administrative distance of 105, which is lower than 110, the router installs the static route into the routing table instead of the OSPF route.

Step-by-Step Solution

1
Identify the destination prefix and protocol Administrative Distance (AD) values
The target prefix is 172.22.0.0/16. Standard OSPF routes have a default AD of 110.
Administrative Distance ranks the trustworthiness of routing information sources.
2
Analyze the configured static route command syntax
In `ip route 172.22.0.0 255.255.0.0 10.0.99.2 105`, the trailing value 105 sets the custom Administrative Distance for this static route.
By default, static routes have an AD of 1 unless a custom value is specified at the end of the command.
3
Compare the AD of the static route against the primary protocol
Since 105<110105 < 110, the router considers the static route more trustworthy than OSPF and places it into the routing table.
Lower administrative distance values win when comparing identical destination prefixes.

Key Concept

Floating Static Route Administrative Distance
Estimated Time:1m 0s
Question 73Question →

A network administrator needs to configure and verify a floating static route on a Cisco IOS router to back up a primary OSPF path (Administrative Distance 110) for destination network 10.50.0.0/2410.50.0.0/24 via next-hop IP 192.168.12.2192.168.12.2. Place the required configuration and verification steps in the correct chronological order.

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Answer

The correct operational sequence begins with entering global configuration mode, configuring the static route with an administrative distance of 120 (higher than OSPF's 110), verifying that OSPF remains the active route in the routing table, simulating a primary path link failure, and finally confirming that the floating static route is inserted into the routing table.
The sequence follows standard configuration and verification workflow: enter global config mode -> apply the floating static route command with AD 120 -> verify primary path retention in RIB -> force failover by shutting down primary path -> verify backup static route installation in RIB.

Step-by-Step Solution

1
Access CLI configuration mode
Router transitions to global configuration prompt
CLI commands altering routing topology must be executed in global configuration mode.
2
Configure the IPv4 floating static route
Route `ip route 10.50.0.0 255.255.255.0 192.168.12.2 120` is added to router candidate table
An Administrative Distance of 120 ensures the static route is floating because it is higher than OSPF's AD of 110.
3
Verify initial RIB state
OSPF route is present in routing table; floating static route is absent
The router selects routes with lower Administrative Distance when multiple paths exist.
4
Simulate primary interface failure
OSPF path is removed from RIB due to dead neighbor / link down
The primary route withdrawal triggers route selection re-evaluation for destination network 10.50.0.0/2410.50.0.0/24.
5
Verify failover to backup floating static route
Static route via 192.168.12.2192.168.12.2 with AD 120 is installed in RIB
With the lower AD route gone, the floating static route becomes the best available path.

Key Concept

Floating Static Route Configuration and Failover Lifecycle
Question 74Question →

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

Show answer & explanation

Answer: ip route 192.168.10.45 255.255.255.255 10.1.1.2

Answer

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

Step-by-Step Solution

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

Key Concept

IPv4 Host Static Routing and Longest Prefix Match
Estimated Time:1m 0s
Question 75Question →

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

Select all that apply

Show answer & explanation

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

Answer

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

Step-by-Step Solution

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

Key Concept

Floating Static Route Configuration and Administrative Distance
Question 76Question →

A network engineer configures an IPv4 static route on a Cisco router using a next-hop IP address: ip route 192.168.50.0 255.255.255.0 10.0.12.2. When the router receives an inbound packet destined for host 192.168.50.25, in what order does the Cisco IOS routing engine process the packet to determine the forwarding path? Arrange the operational steps in the correct chronological sequence from first to last.

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Answer

The correct sequence begins with the packet arrival, followed by performing the initial longest prefix match lookup in the routing table, identifying the next-hop IP address, executing a recursive lookup for that next-hop IP to determine the egress interface, and finally encapsulating and forwarding the packet out the resolved exit interface.
When a static route specifies a next-hop IPv4 address rather than a directly attached exit interface, Cisco IOS must complete a two-step lookup process. First, the router matches the destination IP to the static route entry. Second, it performs a recursive lookup on the next-hop IP address to identify the egress interface. Finally, ARP resolution completes Layer 2 encapsulation, and the frame is transmitted.

Step-by-Step Solution

1
Packet Ingress
The router receives an IPv4 packet addressed to 192.168.50.25 on an ingress interface.
Routing lookup begins only after a packet arrives at the router requiring Layer 3 forwarding.
2
Initial Route Lookup
The routing table identifies the static route 192.168.50.0/24 as the longest prefix match.
Cisco IOS compares the destination IPv4 address against all known routes in the routing table.
3
Next-Hop Extraction
The router identifies 10.0.12.2 as the next-hop address for destination network 192.168.50.0/24.
Static routes configured with an IP address direct traffic to an intermediate next-hop router.
4
Recursive Lookup
The router searches the routing table for 10.0.12.2 and resolves the associated connected exit interface (e.g., GigabitEthernet0/0).
A next-hop static route does not explicitly specify the physical exit interface, requiring a secondary lookup to resolve the route to a connected interface.
5
Frame Encapsulation and Forwarding
The packet is rewritten with Layer 2 headers and forwarded out the resolved exit interface.
Once the egress interface and next-hop MAC address (via ARP) are known, the router can transmit the frame.

Key Concept

Recursive Routing Table Lookup for IPv4 Static Routes
Question 77Question →

An enterprise network administrator is configuring a floating static route on router R1 to serve as a backup path for the corporate subnet 172.16.50.0/24. The primary path is currently learned via internal EIGRP (Administrative Distance 90). Which command correctly configures the backup route so that it remains inactive until the primary EIGRP route fails?

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Answer: ip route 172.16.50.0 255.255.255.0 10.1.1.2 95

Answer

The command 'ip route 172.16.50.0 255.255.255.0 10.1.1.2 95' correctly configures the floating static route.
A floating static route functions as a backup by having an administrative distance configured higher than that of the primary routing protocol. Internal EIGRP has a default administrative distance of 90. Therefore, assigning an administrative distance of 95 to the static route ensures it stays inactive in the routing table until the primary EIGRP route is withdrawn.

Step-by-Step Solution

1
Determine the Administrative Distance (AD) of the primary dynamic routing protocol.
The primary route is learned via internal EIGRP, which has a default administrative distance of 90.
A floating static route must have an administrative distance higher than the active primary route to serve as an inactive backup.
2
Select an administrative distance value for the static route that exceeds the primary AD.
Specifying an AD of 95 ensures the static route is kept out of the routing table while the EIGRP route remains active.
Cisco IOS installs routes with lower administrative distance values first into the routing table.

Key Concept

Floating Static Routes and Administrative Distance
Question 78Question →

A network administrator is configuring static routes on router R1 to reach two remote networks: Subnet A (10.2.2.0/2410.2.2.0/24) connected across a point-to-point serial interface (Serial0/0/0), and Subnet B (10.3.3.0/2410.3.3.0/24) connected across a multiaccess Ethernet interface (GigabitEthernet0/0, with next-hop IP address 192.168.1.2192.168.1.2). Which two static route configuration commands follow Cisco IOS best practices and prevent unnecessary ARP resolution overhead?

Select all that apply

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Answer: ip route 10.2.2.0 255.255.255.0 Serial0/0/0; ip route 10.3.3.0 255.255.255.0 192.168.1.2

Answer

The two correct static route statements are 'ip route 10.2.2.0 255.255.255.0 Serial0/0/0' for the point-to-point serial connection and 'ip route 10.3.3.0 255.255.255.0 192.168.1.2' for the multiaccess Ethernet connection.
In Cisco IOS IPv4 static routing, the ideal syntax depends on the physical media type of the outgoing interface. For point-to-point links like Serial interfaces, referencing the exit interface directly is complete and efficient because there is only one potential receiver on the segment. For broadcast multiaccess links like Ethernet, referencing the next-hop IPv4 address is mandatory for clean Layer 2 frame encapsulation without generating excessive ARP broadcasts.

Step-by-Step Solution

1
Determine the interface media type for Subnet A (10.2.2.0/2410.2.2.0/24).
Subnet A uses a point-to-point serial link (Serial0/0/0).
On point-to-point links, specifying the local exit interface directly avoids next-hop IP recursive lookups without causing Layer 2 MAC resolution issues.
2
Determine the interface media type for Subnet B (10.3.3.0/2410.3.3.0/24).
Subnet B uses a broadcast multiaccess Ethernet link (GigabitEthernet0/0).
On Ethernet networks, specifying the next-hop IPv4 address (192.168.1.2192.168.1.2) allows the router to resolve the specific next-hop gateway MAC address, preventing proxy ARP overhead.
3
Verify Cisco IOS syntax compliance.
Confirm standard dotted-decimal subnet mask formatting (255.255.255.0).
Cisco IOS static routes mandate subnet masks ('ip route <prefix> <mask> {ip-address | exit-interface}').

Key Concept

IPv4 Static Route Syntax and Next-Hop Resolution on Point-to-Point vs Multiaccess Interfaces
Question 79Question →

A network administrator configures R1 with a primary dynamic route learned via OSPF (Administrative Distance 110110) and a floating static backup route (Administrative Distance 130130) targeting network 10.5.0.0/2410.5.0.0/24. Place the operational steps performed by R1 in the correct chronological sequence following an interface link failure on the primary path.

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Answer

The correct operational sequence begins with link failure detection, followed by OSPF route withdrawal from the RIB, candidate route evaluation by the router, installation of the floating static route into the RIB, and finally updating the CEF FIB table for data plane forwarding.
When a primary link fails, the physical interface status drop triggers OSPF adjacency removal, which withdraws the OSPF route (AD=110AD = 110) from the RIB. R1 then evaluates candidate routes and finds the floating static route (AD=130AD = 130). Because no lower AD route exists, R1 installs the floating static route into the RIB and programs the CEF FIB table to direct traffic to the backup next-hop.

Step-by-Step Solution

1
Identify the primary failure event
Interface status changes to down/down.
Physical link down is the initial event triggering interface removal.
2
Process routing protocol metric/state updates
OSPF route with Administrative Distance 110 is purged from the RIB.
Routes tied to down interfaces or lost adjacencies are immediately withdrawn.
3
Search for remaining active routes
R1 checks candidate static and dynamic entries for network 10.5.0.0/24.
The router control plane must find another valid route entry to reach the prefix.
4
Select and install the best remaining candidate route
Floating static route with Administrative Distance 130 is chosen and placed into the RIB.
Floating static routes only enter the RIB when lower AD routes are purged.
5
Program the forwarding plane
Cisco Express Forwarding (CEF) updates the Forwarding Information Base (FIB).
Data plane hardware tables must sync with RIB control plane updates to forward user traffic.

Key Concept

Floating Static Route Failover & Convergence Order
Estimated Time:1m 30s
Question 80Question →

An administrator needs to configure a backup static route on router R1 to reach destination network 10.20.30.0/2410.20.30.0/24 only if the primary path learned via internal EIGRP (Administrative Distance 9090) becomes unavailable. The next-hop IPv4 address for the backup path is 192.168.1.2192.168.1.2. Which command must be entered on router R1 to achieve this objective?

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Answer: ip route 10.20.30.0 255.255.255.0 192.168.1.2 95

Answer

The command 'ip route 10.20.30.0 255.255.255.0 192.168.1.2 95' correctly configures a floating static route with an Administrative Distance higher than EIGRP.
The command specifying destination network 10.20.30.0, subnet mask 255.255.255.0, next-hop IP 192.168.1.2, and Administrative Distance 95 correctly establishes a floating static route. Because the AD of 95 is higher than Internal EIGRP's AD of 90, the router will use EIGRP during normal operations and only insert this static route into the routing table if the EIGRP path goes down.

Step-by-Step Solution

1
Identify the standard Cisco IOS IPv4 static route syntax.
Syntax: 'ip route <destination-network> <subnet-mask> <next-hop-ip> [administrative-distance]'
Correct command structure is required for syntax validity on Cisco routers.
2
Determine the required Administrative Distance (AD) for a floating static backup route.
AD must be greater than the primary route protocol's AD (90 for Internal EIGRP). Thus, AD = 95.
Routes with lower AD are preferred in the IP routing table. Setting AD higher than 90 ensures the static route remains inactive until EIGRP fails.
3
Combine the network parameters into the final command.
ip route 10.20.30.0 255.255.255.0 192.168.1.2 95
Matches destination 10.20.30.0/2410.20.30.0/24, next-hop 192.168.1.2192.168.1.2, and floating AD 95.

Key Concept

Floating Static Routes and Administrative Distance
Estimated Time:1m 15s
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