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IP Connectivity

493 questions

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Question 461Question →

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.

Drag items to arrange them in the correct order

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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 462Question →

A network administrator is reviewing the output of the 'show ip route' command on a Cisco IOS router. Match each routing table component or source code on the left with its correct functional definition on the right.

Click a left item, then click its matching right item

Items

Administrative Distance
Metric
Prefix Length
Source Code 'D'

Matches

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Answer

Administrative Distance matches the trustworthiness of the route source; Metric matches the protocol-specific path cost; Prefix Length matches the subnet mask bit count used for longest prefix matching; Source Code 'D' matches routes dynamically learned via EIGRP.
Each field in a Cisco IPv4 routing table entry provides distinct information: Administrative Distance prioritizes between routing protocols; Metric determines the optimal path within a single protocol; Prefix Length defines mask length for longest prefix match logic; and the code 'D' identifies routes learned via EIGRP.

Step-by-Step Solution

1
Identify the definition of Administrative Distance.
Administrative Distance rates the trustworthiness of routing protocol sources.
It allows the router to choose the preferred route source when the same network prefix is advertised by different routing sources.
2
Identify the role of Metric in a routing table entry.
Metric represents path cost calculated by an individual routing protocol.
When multiple candidate paths to a destination exist within the same protocol, the route with the lowest metric value is selected.
3
Determine the function of Prefix Length.
Prefix length denotes the subnet mask bit count and determines match specificity.
Routers evaluate prefix lengths to perform longest prefix matching as the primary criteria during packet lookup.
4
Identify the Cisco IOS routing table source code indicator 'D'.
'D' corresponds to EIGRP-learned routes.
Cisco utilizes 'D' for EIGRP (referencing its DUAL algorithm) because 'E' was historically assigned to EGP.

Key Concept

Routing Table Components and Operational Roles
Question 463Question →

A network engineer is configuring a floating static route on a Cisco router to serve as a backup path for destination network 172.20.10.0/24 via next-hop IP 10.1.1.2. The primary route to this network is currently learned via eBGP, which has a default administrative distance of 20. The engineer needs to assign an administrative distance of 25 to the backup route so that it only enters the routing table if the primary route fails. What value should complete the configuration command?

Fill in the blanks below

ip route 172.20.10.0 255.255.255.0 10.1.1.2
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Answer

25
In Cisco IOS, a floating static route is created by appending a numerical administrative distance at the end of the `ip route` command. Specifying 25 configures the static route with an administrative distance higher than eBGP (AD 20), ensuring it remains floating (inactive) until the primary route drops out of the routing table.

Step-by-Step Solution

1
Identify the administrative distance of the primary route protocol.
The primary path is learned via eBGP, which has a default administrative distance of 20.
A floating static route must be configured with an administrative distance higher than the primary path so it remains inactive until failure.
2
Determine the trailing numerical argument for the Cisco IOS static route command.
Appending 25 to the end of the `ip route` syntax sets the administrative distance of the static route to 25.
Cisco IOS uses the optional trailing distance parameter in the `ip route <prefix> <mask> <next-hop> [distance]` command syntax.

Key Concept

Floating Static Route Configuration and Administrative Distance
Question 464Question →

A Cisco router is booted with the following interfaces configured and in the up/up state:

- Loopback0: 10.10.10.1/32
- Loopback1: 172.16.100.1/32
- GigabitEthernet0/0: 192.168.10.1/24
- GigabitEthernet0/1: 192.168.200.1/24

An administrator configures OSPFv2 on the router using the following commands:

text
Router(config)# router ospf 1
Router(config-router)# network 192.168.10.0 0.0.0.255 area 0

No `router-id` command is specified. Which IP address will OSPFv2 select as the Router ID for process 1?

Show answer & explanation

Answer: 172.16.100.1

Answer

172.16.100.1 is selected because it is the highest IPv4 address among all active loopback interfaces on the router.
OSPFv2 uses a strict order of precedence to determine the Router ID: 1) Explicitly configured `router-id` command, 2) Highest IPv4 address of any active (up/up) loopback interface, 3) Highest IPv4 address of any active non-loopback interface. Since no `router-id` command is configured, OSPF inspects the active loopback interfaces (10.10.10.1 and 172.16.100.1) and selects the highest IP address (172.16.100.1). It is not required for OSPF to be enabled on that loopback interface.

Step-by-Step Solution

1
Evaluate manual Router ID configuration
No explicit `router-id` command was executed under the OSPF process.
Explicit configuration always takes first priority in OSPF Router ID election.
2
Evaluate active loopback interfaces
Two active loopbacks exist: Loopback0 (10.10.10.1) and Loopback1 (172.16.100.1).
If no manual Router ID exists, OSPF evaluates active loopback interfaces before non-loopback physical interfaces.
3
Select the highest loopback IP address
172.16.100.1 is numerically higher than 10.10.10.1.
OSPF selects the highest IPv4 address among active loopback interfaces regardless of whether OSPF is enabled on those specific loopbacks.

Key Concept

OSPFv2 Router ID Election Priority Hierarchy
Estimated Time:1m 0s
Question 465Question →

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 466Question →

A Cisco router has OSPFv2 process 1 initialized without an explicitly configured router ID. The interface operational statuses and IPv4 address assignments are as follows:

- Loopback0: 172.25.1.1/32 (administratively down, down/down)
- Loopback1: 10.120.5.1/32 (up/up)
- Loopback2: 10.80.99.1/32 (up/up)
- GigabitEthernet0/0: 192.168.50.1/24 (up/up)

What IPv4 address will OSPFv2 select as the router ID for process 1?

Show answer & explanation

Answer: 10.120.5.1

Answer

10.120.5.1
OSPF selects its Router ID using the following strict hierarchy: 1) Explicitly configured `router-id` command, 2) Highest IPv4 address among active (up/up) loopback interfaces, 3) Highest IPv4 address among active (up/up) physical interfaces. Here, Loopback1 (10.120.5.1) and Loopback2 (10.80.99.1) are both active loopbacks. Since 10.120.5.1 is numerically higher than 10.80.99.1, 10.120.5.1 is chosen.

Step-by-Step Solution

1
Check for a manually configured router ID
No explicit `router-id` command was configured under the OSPF process.
Manual configuration always takes highest precedence in OSPF router ID election.
2
Evaluate operational loopback interfaces
Loopback1 (10.120.5.1) and Loopback2 (10.80.99.1) are both active (up/up). Loopback0 is down/down and excluded.
Only operational (up/up) interfaces are eligible for automatic election. Active loopback interfaces take precedence over physical interfaces.
3
Compare IP addresses of active loopbacks to select the highest numerical IP
Comparing 10.120.5.1 and 10.80.99.1, 10.120.5.1 is numerically higher because 120>80120 > 80 in the second octet.
OSPF selects the highest IPv4 address among all operational loopback interfaces.

Key Concept

OSPFv2 Router ID Election Logic
Question 467Question →

An administrator intends to deploy a floating static route on router R1 to serve as a backup path for internal network 10.100.50.0/2410.100.50.0/24, which is primarily learned via Internal EIGRP (administrative distance 90). Following the configuration, traffic immediately shifts to the secondary link despite the primary link remaining fully operational.

Which configuration mistake caused the static route to preempt the primary EIGRP route in the routing table?

Show answer & explanation

Answer: The static route was assigned an administrative distance value lower than 90, causing it to take precedence over the EIGRP route.

Answer

The static route was assigned an administrative distance value lower than 90, causing it to take precedence over the EIGRP route.
Cisco IOS routers evaluate Administrative Distance (AD) to determine which routing source to trust when multiple sources offer routes to the exact same destination prefix. Lower AD values are preferred. Internal EIGRP has a default AD of 90. For a static route to serve as a floating backup, its AD must be configured to a value strictly greater than 90 (e.g., 95 or 130). If the administrator configures an AD lower than 90 (or omits the AD parameter, which defaults to 1), the static route will be preferred over EIGRP and immediately installed into the routing table as the active route.

Step-by-Step Solution

1
Analyze the primary routing protocol's Administrative Distance (AD).
Internal EIGRP has a default AD of 90.
Cisco IOS selects routes with the lowest administrative distance when multiple sources advertise the identical destination network prefix.
2
Determine the requirement for a floating static route to act as a backup.
The floating static route must have an AD strictly greater than 90 so it stays out of the routing table while EIGRP is active.
If the configured static route has an AD lower than 90 (or defaults to 1), the router prefers the static route over EIGRP immediately.
3
Identify the cause of immediate preemption.
Assigning an AD lower than 90 caused the router to install the static route into the routing table over the active EIGRP route.
Routes with lower administrative distance values take administrative preference in the Cisco IOS routing table installation process.

Key Concept

Administrative Distance Precedence in Floating Static Routes
Question 468Question →

Router R1 learns the destination network 10.50.0.0/1610.50.0.0/16 dynamically via internal EIGRP, which has a default Administrative Distance (AD) of 90. A network administrator wants to configure a floating static route pointing to next-hop 192.168.12.2192.168.12.2 to serve as a backup path when the EIGRP route fails. Which two conditions or behaviors apply to this floating static route implementation? (Select two.)

Select all that apply

Show answer & explanation

Answer: The floating static route must be configured with an Administrative Distance value greater than 90.; The floating static route will be placed into the active routing table only when the primary EIGRP route is removed.

Answer

To configure a functional floating static route for an EIGRP primary path, the static route must specify an Administrative Distance greater than 90 (the default EIGRP AD). Consequently, the backup route will only be installed into the active routing table when the lower-AD EIGRP route disappears.
A floating static route acts as a backup mechanism by using an Administrative Distance (AD) higher than that of the primary route (in this case, EIGRP AD of 90). Cisco IOS populates the active routing table with the lowest AD available; thus, the static route stays out of the routing table until the primary route fails and is withdrawn.

Step-by-Step Solution

1
Identify the Administrative Distance (AD) of the primary routing protocol.
Internal EIGRP has a default AD of 90.
Floating static routes rely on AD comparison to remain dormant until the primary route fails.
2
Determine the required Administrative Distance for the backup floating static route.
The static route's AD must be set higher than 90 (e.g., 95 or 130).
If configured with a lower AD (such as 80 or 1), the static route would override the EIGRP path during normal operation.
3
Analyze how Cisco IOS handles routing table selection for multiple sources.
Only the path with the lowest AD is placed in the active routing table.
The floating static route remains inactive in the background and is only installed when the EIGRP prefix is removed due to network failure.

Key Concept

Floating Static Routes and Administrative Distance
Question 469Question →

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

Show answer & explanation

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 470Question →

Two Cisco routers, R1 and R2, are directly connected via their GigabitEthernet0/0 interfaces on the 192.168.12.0/24 network segment. OSPFv2 is initialized on both routers. R1 has its GigabitEthernet0/0 interface placed into OSPF Area 0, while R2 has its GigabitEthernet0/0 interface placed into OSPF Area 10. All other OSPF interface configurations use default settings. What will be the observed result when an administrator executes the command `show ip ospf neighbor` on R1?

Show answer & explanation

Answer: No neighbor entry for R2 will be displayed in the neighbor table.

Answer

No neighbor entry for R2 will be displayed in the neighbor table because Hello packets containing mismatched OSPF Area IDs are dropped during initial packet processing.
For OSPF neighbors to form an adjacency, specific Hello packet fields must match between connected interfaces: Area ID, Subnet Mask, Hello and Dead intervals, and Authentication. When R1 receives Hello packets from R2 with Area ID 10 while R1 is configured in Area 0, R1 discards the packets. Because valid Hello packets are never processed, R1 does not initialize a neighbor data structure for R2, leaving the OSPF neighbor table completely empty.

Step-by-Step Solution

1
Analyze OSPF Hello packet validation criteria
Identified that Area ID, Hello/Dead intervals, Subnet Mask (on broadcast networks), and Authentication parameters must match exactly between connected interfaces.
OSPF requires neighbor interfaces to share identical primary link configuration parameters before forming an adjacency.
2
Evaluate the effect of an Area ID mismatch
R1 (Area 0) receives Hello packets from R2 containing Area 10 and drops them immediately.
When a received OSPF Hello header contains an Area ID differing from the receiving interface's configured Area ID, the packet is invalidated.
3
Determine the resulting neighbor table state on R1
R1 does not record R2 in any OSPF state (Down/INIT/2-WAY/FULL).
Without processing incoming Hello packets, R1 never discovers R2, resulting in no entry in `show ip ospf neighbor`.

Key Concept

OSPFv2 Hello Packet Parameter Matching for Neighbor Adjacency
Estimated Time:1m 15s
Question 471Question →

Four routers (R1, R2, R3, and R4) are connected to a shared Ethernet switch in OSPFv2 Area 0. R1 (Router ID 1.1.1.1, interface priority 1) boots up first and completes initialization. Next, R2 (Router ID 2.2.2.2, interface priority 1) boots up and joins the network segment. Several minutes later, R3 (Router ID 3.3.3.3, interface priority 255) and R4 (Router ID 4.4.4.4, interface priority 0) are booted up and added to the OSPF segment. Assuming no OSPF processes are restarted or cleared, which router serves as the Designated Router (DR) on this multiaccess segment?

Show answer & explanation

Answer: R1

Answer

R1 remains the Designated Router (DR) because OSPF DR elections are non-preemptive.
OSPF DR/BDR elections are non-preemptive on broadcast multiaccess networks. Since R1 booted first and was elected Designated Router, it retains the DR role continuously regardless of new routers with higher priorities or higher Router IDs joining the network later.

Step-by-Step Solution

1
Evaluate the boot order and initial election outcome
R1 boots first and becomes the DR. R2 boots second and becomes the BDR.
When R1 boots, no existing DR exists on the segment, so R1 assumes the DR role. R2 joins next and claims the vacant BDR role.
2
Analyze the impact of adding R3 and R4 to an operational segment
R3 and R4 form adjacencies but do not trigger a new DR election.
OSPF DR/BDR elections are non-preemptive. Once a DR and BDR are active on a broadcast multiaccess segment, newly added routers with higher priority or higher Router IDs will not preempt the current DR or BDR.
3
Determine the final DR role assignment
R1 maintains its role as DR.
Because R1 has not failed or restarted its OSPF process, it continues functioning as the active DR.

Key Concept

OSPFv2 DR/BDR Non-Preemption
Estimated Time:1m 30s
Question 472Question →

A network administrator is designing a high-availability default gateway architecture for VLAN 10 (subnet 10.1.10.0/24) using two Layer 3 distribution switches. Switch-1 is configured with physical interface IP address 10.1.10.2/24 and Switch-2 is configured with physical interface IP address 10.1.10.3/24. The administrator is evaluating protocol characteristics between HSRPv2 and VRRPv3. Which two statements correctly describe operational differences and IP addressing rules between these protocols? (Select two.)

Select all that apply

Show answer & explanation

Answer: VRRPv3 allows the virtual IP address to match Switch-1's physical interface IP address (10.1.10.2), automatically designating Switch-1 as the IP address owner with a default priority of 255.; HSRPv2 sends control messages to the IPv4 multicast destination address 224.0.0.102, whereas VRRP (v2/v3) sends advertisement messages to the IPv4 multicast destination address 224.0.0.18.

Answer

The two correct statements are: VRRPv3 allows the virtual IP address to match a physical interface IP address (designating that router as the IP address owner with priority 255), and HSRPv2 uses multicast destination 224.0.0.102 while VRRP uses 224.0.0.18.
VRRPv3 supports IP address ownership where the virtual IP address matches a router's physical interface IP address, automatically elevating its priority to 255 (the maximum). In addition, HSRPv2 uses multicast group address 224.0.0.102 for hello packets, while VRRP uses multicast address 224.0.0.18.

Step-by-Step Solution

1
Analyze virtual IP assignment rules for HSRP vs VRRP
HSRP requires the virtual IP address to be distinct from all physical interface IP addresses assigned to routers in the group. VRRP allows IP address ownership, where the virtual IP matches a physical interface IP address and sets priority to 255.
Verifies whether IP ownership is supported in HSRP vs VRRP.
2
Verify multicast destination addresses for HSRPv2 and VRRP
HSRPv1 uses 224.0.0.2, HSRPv2 uses 224.0.0.102, and VRRP (both v2 and v3) uses 224.0.0.18.
Differentiates protocol transport mechanics across FHRP implementations.
3
Evaluate default preemption mechanisms
HSRP disables preemption by default (higher priority standby router will not take over active state without explicit configuration). VRRP enables preemption by default.
Eliminates incorrect claims regarding preemption defaults.

Key Concept

FHRP protocol differences: VRRP IP address ownership, HSRP virtual IP uniqueness requirements, protocol multicast addresses, and default preemption settings.
Question 473Question →

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.

Drag items to arrange them in the correct order

Show answer & explanation

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 474Question →

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?

Show answer & explanation

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
Question 475Question →

A Cisco router's IPv4 routing table contains four active static routes to various destination networks:

- `ip route 0.0.0.0 0.0.0.0 192.168.1.4`
- `ip route 10.10.0.0 255.255.0.0 192.168.1.1`
- `ip route 10.10.4.0 255.255.255.0 192.168.1.2`
- `ip route 10.10.4.16 255.255.255.240 192.168.1.3 110`

When the router receives an IP packet destined for 10.10.4.2510.10.4.25, which next-hop IP address will the router select to forward the packet?

Show answer & explanation

Answer: 192.168.1.3

Answer

192.168.1.3 is selected because 10.10.4.16/28 provides the longest matching subnet mask for the destination address 10.10.4.25.
When a router makes a packet forwarding decision, it compares the destination IP address (10.10.4.2510.10.4.25) against all installed routes in its routing table and selects the route with the most specific match (longest subnet mask). The destination address falls into the subnet 10.10.4.16/2810.10.4.16/28 (10.10.4.1610.10.4.16 to 10.10.4.3110.10.4.31). Since /28/28 is longer than /24/24, /16/16, and /0/0, the router selects this entry and forwards the packet to next-hop 192.168.1.3192.168.1.3. Administrative Distance is irrelevant during the actual lookup phase of already-installed routes.

Step-by-Step Solution

1
Analyze the destination IPv4 address against all routing table entries
Destination 10.10.4.25 matches four routes: 0.0.0.0/0, 10.10.0.0/16, 10.10.4.0/24, and 10.10.4.16/28 (range 10.10.4.16 - 10.10.4.31).
Routing lookup evaluates all routes installed in the routing table to find candidates.
2
Apply the Longest Prefix Match (LPM) rule to select the forwarding route
The /28 subnet mask is longer and more specific than /24, /16, or /0.
Routers always forward packets based on the longest matching prefix length regardless of Administrative Distance.
3
Determine the next-hop IPv4 address associated with the selected route
The 10.10.4.16/28 route points to next-hop 192.168.1.3.
The packet is forwarded to the next-hop IP associated with the winning prefix match.

Key Concept

Longest Prefix Match forwarding decision logic in IPv4 Routing
Question 476Question →

A Cisco router receives an IPv4 packet destined for host 192.168.2.50192.168.2.50. The router's routing table contains a static route configured as `ip route 192.168.2.0 255.255.255.0 10.1.1.2`. Which sequence correctly orders the internal packet processing and recursive routing lookup steps executed by the router 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 packet requiring a recursive static route lookup is: First, match the destination IP address against the routing table using longest prefix match. Second, extract the static route entry pointing to next-hop IP 10.1.1.2. Third, perform a recursive lookup for 10.1.1.2. Fourth, resolve the egress interface to GigabitEthernet0/1 via the connected route. Fifth, perform ARP resolution for 10.1.1.2 and encapsulate/forward the frame out GigabitEthernet0/1.
The correct sequence begins with comparing the incoming packet's destination IP address against the routing table using longest prefix matching. Upon matching the static route for 192.168.2.0/24, the router retrieves the next-hop IP address (10.1.1.2). Because the static route was configured with only a next-hop IP address rather than an exit interface, the router must execute a second (recursive) lookup to resolve how to reach 10.1.1.2. The recursive lookup matches a directly connected route (10.1.1.0/24 on GigabitEthernet0/1), establishing the outbound interface. Finally, ARP resolves the MAC address corresponding to 10.1.1.2, allowing the router to encapsulate and transmit the frame.

Step-by-Step Solution

1
Perform initial routing table lookup for destination IP 192.168.2.50192.168.2.50.
Matches static route prefix `192.168.2.0/24` based on longest prefix match.
Routers evaluate incoming packet destinations against all active routes in the routing table to find the best match.
2
Extract the next-hop IP address 10.1.1.210.1.1.2 from the matched static route.
Determines that packets must be sent toward next-hop IP address 10.1.1.210.1.1.2.
When a static route points to an IP address rather than an interface, the router must identify where to send the traffic next.
3
Execute a recursive lookup in the routing table for IP 10.1.1.210.1.1.2.
Searches for an active routing entry covering IP 10.1.1.210.1.1.2.
The router needs to determine which exit interface connects to the network containing next-hop address 10.1.1.210.1.1.2.
4
Resolve next-hop IP 10.1.1.210.1.1.2 to connected subnet route `10.1.1.0/24` on GigabitEthernet0/1.
Identifies GigabitEthernet0/1 as the physical outbound interface.
The recursive process ends when the next-hop IP resolves to a directly connected interface.
5
Perform ARP resolution for 10.1.1.210.1.1.2 and transmit frame.
Encapsulates packet in Ethernet frame with next-hop MAC address and transmits out GigabitEthernet0/1.
Layer 3 packet processing concludes with Layer 2 address resolution and frame transmission out the designated egress interface.

Key Concept

IPv4 Static Route Recursive Lookup Process
Estimated Time:1m 30s
Question 477Question →

An administrator is configuring IPv4 static routes on a Cisco IOS router connected to adjacent networks via both point-to-point serial and multiaccess Ethernet interfaces. Which two statements correctly describe the behavior of these IPv4 static route configurations? (Select two.)

Select all that apply

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Answer: Configuring a static route specifying only an Ethernet exit interface forces the router to resolve destination IP addresses using ARP, increasing ARP table size and processing overhead.; Configuring a static route specifying only a next-hop IP address requires the router to perform a recursive lookup in the routing table to identify the outgoing interface.

Answer

The correct statements are that specifying only an Ethernet exit interface forces the router to resolve destination host IPs using ARP (increasing processing and memory load), and specifying only a next-hop IP address requires a recursive lookup in the routing table to determine the egress interface.
Specifying only an Ethernet exit interface causes the router to issue ARP requests for every destination IP address, inflating the ARP table. Specifying only a next-hop IP address forces the router to perform a recursive routing lookup to identify the appropriate outbound interface.

Step-by-Step Solution

1
Analyze static route next-hop IP resolution behavior
Identified that next-hop static routes require a recursive lookup step
When a route specifies only a next-hop IP address, the router must search its routing table again to find the interface through which that next-hop address is reachable.
2
Analyze static route exit-interface behavior on multiaccess networks
Identified that specifying only an exit interface on Ethernet causes excessive ARP requests
On multiaccess segments, omitting the next-hop IP causes the router to treat every remote destination host IP as directly attached to the local link, triggering ARP resolution for each destination.
3
Evaluate administrative distance for route selection
Identified that an administrative distance of 110 does not take precedence over OSPF
OSPF uses a default administrative distance of 110. To override an OSPF route, a static route must have a lower administrative distance (e.g., default AD of 1).

Key Concept

IPv4 Static Routing Next-Hop Resolution and Exit Interface Selection
Question 478Question →

A network administrator is migrating a VLAN gateway infrastructure from VRRP to HSRP version 2 on Cisco IOS routers. Under the previous VRRP setup, Router R1 had its physical interface IP address configured as 192.168.10.1/24192.168.10.1/24 and served as the VRRP IP address owner by using 192.168.10.1192.168.10.1 as the virtual IP address.

During the migration, the administrator enters the following commands on Router R1's GigabitEthernet0/0 interface:
text
RouterR1(config)# interface gigabitethernet 0/0
RouterR1(config-if)# ip address 192.168.10.1 255.255.255.0
RouterR1(config-if)# standby version 2
RouterR1(config-if)# standby 10 ip 192.168.10.1

What is the outcome of executing the `standby 10 ip 192.168.10.1` command on Router R1?

Show answer & explanation

Answer: Cisco IOS rejects using the interface physical IP address as the HSRP virtual IP address, resulting in a configuration error.

Answer

Cisco IOS rejects using the interface physical IP address as the HSRP virtual IP address, resulting in a configuration error.
Unlike VRRP, which allows a router interface to be the IP address owner by assigning its physical IP address as the virtual IP address (which sets its priority automatically to 255255), Cisco HSRP (both v1 and v2) requires the virtual IP address to be an unused IP address on the IP subnet. Attempting to assign the local interface's physical IP address as the HSRP virtual IP address will be rejected by Cisco IOS.

Step-by-Step Solution

1
Analyze VRRP versus HSRP virtual IP address assignment rules.
VRRP allows a router to act as the IP address owner where the virtual IP address is identical to the router's physical interface IP address (assigning priority 255255). In contrast, Cisco HSRP (both v1 and v2) strictly requires the virtual IP address to be a unique IP address on the subnet that is not assigned to any physical router interface.
Understanding protocol design differences prevents invalid configurations during network migrations.
2
Evaluate the CLI command result on Router R1.
Entering `standby 10 ip 192.168.10.1` while GigabitEthernet0/0 has the physical IP address 192.168.10.1192.168.10.1 causes Cisco IOS to generate an error indicating the virtual IP address cannot match the local physical IP address.
HSRP relies on distinct virtual and physical IP addressing to maintain dual operational capability for ARP and ICMP handling.

Key Concept

HSRP Virtual IP Address Uniqueness Constraint vs. VRRP IP Address Ownership
Estimated Time:1m 15s
Question 479Question →

A network engineer is comparing First Hop Redundancy Protocols (FHRP) for a multi-vendor enterprise network deployment. The evaluation focuses on the operational defaults and protocol parameters of Cisco HSRPv1 and industry-standard VRRPv2. Which two statements accurately describe the operational differences between HSRPv1 and VRRPv2? (Choose two.)

Select all that apply

Show answer & explanation

Answer: VRRPv2 uses the multicast IP address 224.0.0.18 for control traffic, whereas HSRPv1 uses 224.0.0.2.; VRRPv2 enables preemption by default for the Master router role, whereas HSRPv1 disables preemption by default for the Active router role.

Answer

The correct options state that VRRPv2 uses multicast IP 224.0.0.18 while HSRPv1 uses 224.0.0.2, and that VRRPv2 has preemption enabled by default while HSRPv1 has preemption disabled by default.
The correct statements correctly identify key operational differences: VRRPv2 sends control advertisements to multicast IP 224.0.0.18 whereas HSRPv1 uses 224.0.0.2, and VRRPv2 has preemption enabled by default whereas HSRPv1 requires preemption to be explicitly configured.

Step-by-Step Solution

1
Analyze multicast destination IP address differences between HSRPv1 and VRRPv2.
HSRPv1 control traffic is destined to 224.0.0.2224.0.0.2 (UDP port 1985). VRRPv2 control traffic is destined to 224.0.0.18224.0.0.18 (IP protocol 112).
This confirms the statement regarding protocol multicast IP addressing is accurate.
2
Analyze default preemption behavior for both protocols.
VRRPv2 has preemption enabled by default. HSRPv1 has preemption disabled by default.
This confirms the statement regarding preemption defaults is accurate.
3
Evaluate distractor options concerning virtual IP assignment and virtual MAC address ranges.
VRRP allows virtual IP matching (IP address owner), while HSRP rejects it. HSRPv1 uses MAC prefix 0000.0c07.acXX, while VRRPv2 uses 0000.5e00.01XX.
Both incorrect choices swap the characteristic traits between HSRP and VRRP.

Key Concept

HSRPv1 vs VRRPv2 Protocol Characteristics and Defaults
Question 480Question →

A network administrator is designing a First Hop Redundancy Protocol (FHRP) deployment for a LAN segment. The design requirement dictates that the virtual default gateway IP address configured for host devices must be identical to the physical IP address assigned to the primary router's GigabitEthernet0/0 interface. Which protocol selection and operational characteristic accurately satisfies this design requirement?

Show answer & explanation

Answer: VRRP, because it permits the virtual IP address to match a physical interface IP address, making that router the IP address owner with a default priority of 255.

Answer

VRRP allows the virtual IP address to match a router's physical interface IP address, designating that router as the IP address owner with an effective priority of 255.
In VRRP, a router can be configured to use its own physical interface IP address as the virtual IP address for the redundancy group. When this occurs, the router becomes the IP address owner and its priority is fixed at 255, ensuring it acts as the Master router whenever its interface is active.

Step-by-Step Solution

1
Analyze the FHRP requirement for IP address ownership.
The scenario requires the virtual default gateway IP address to be identical to the primary router's physical interface IP address.
Different FHRP protocols have distinct rules regarding whether the virtual IP address can overlap with an interface's assigned physical IP.
2
Evaluate HSRP (v1 and v2) behavior regarding physical IP address assignment.
HSRP requires the virtual IP address to be a unique IP address on the subnet that is not assigned to any physical interface of the participating routers.
Attempting to assign a physical IP address as the HSRP virtual IP results in a CLI configuration error in Cisco IOS.
3
Evaluate VRRP (v2 and v3) behavior regarding physical IP address assignment.
VRRP explicitly supports assigning the physical interface IP address of a router as the VRRP virtual IP address.
When a router's physical IP matches the VRRP virtual IP, that router assumes the role of IP Address Owner and its operational priority is automatically set to 255 (the maximum possible priority).

Key Concept

VRRP IP Address Ownership vs HSRP Virtual IP Restrictions
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