Cisco CCNA (200-301) — All Questions

What does the 'passive-interface' command accomplish under an OSPF routing process?

• a.It shuts the interface down administratively until an OSPF neighbor is detected on the link The router then floods a hello out that interface every ten seconds regardless.
• b.It stops OSPF hellos on the interface so no adjacency forms, while the network is still advertised✓
• c.It causes the interface to send hellos more frequently to speed up neighbor discovery
• d.It converts the interface into a point-to-point type and disables DR/BDR election

A passive interface stops OSPF from sending or processing hello packets out that interface, so no adjacency can form there. However, if the interface's network is included by a network statement, the prefix is still advertised into OSPF. This is typically used on LAN interfaces facing end hosts where no OSPF neighbor should exist.

Two OSPF routers reach the 2-WAY state but never progress to FULL on a broadcast segment. Which explanation is most consistent with this behavior?

• a.They are both non-DR/non-BDR (DROTHER) routers, so 2-WAY with each other is normal and expected✓
• b.The MTU values on the two interfaces disagree, which stalls the exchange at EXSTART
• c.One router has a duplicate router ID, which resets the adjacency continuously
• d.Their hello and dead timers are mismatched, preventing any neighbor relationship at all A reload of both devices is the only supported way to clear this stuck condition.

On a multiaccess broadcast network, DROTHER routers form full adjacencies only with the DR and BDR, and they intentionally remain in the 2-WAY state with each other. This is normal, not a fault. A timer mismatch would prevent 2-WAY entirely, and an MTU mismatch typically stalls the exchange at EXSTART/EXCHANGE, not 2-WAY.

Using OSPF's default reference bandwidth of 100 Mbps, what cost does a router assign to a 100 Mbps FastEthernet interface?

• a.0
• b.1✓
• c.100
• d.10

OSPF cost equals reference bandwidth divided by interface bandwidth: 100 Mbps / 100 Mbps = 1. Because any link at or above 100 Mbps rounds to a minimum cost of 1, gigabit and faster interfaces are indistinguishable under the default reference. Engineers raise the reference bandwidth to differentiate high-speed links.

An engineer sets 'auto-cost reference-bandwidth 10000' (10 Gbps) on all OSPF routers. What cost does a 1 Gbps interface now receive?

• a.1000, reflecting the ratio expressed directly in megabits per second
• b.1, because the reference and interface both operate in the gigabit-and-above range
• c.100
• d.10✓

With the reference bandwidth set to 10,000 Mbps, the cost of a 1 Gbps (1000 Mbps) link is 10000 / 1000 = 10. Raising the reference lets OSPF distinguish 1 Gbps, 10 Gbps, and faster links that would all be cost 1 under the default. The reference bandwidth must be set identically on every router for consistent path selection.

With the default 100 Mbps reference bandwidth, what OSPF cost is calculated for a T1 serial link running at 1.544 Mbps?

• a.24
• b.1544, because OSPF uses the raw bandwidth value in kilobits as the cost
• c.64✓
• d.1

OSPF cost is 100 Mbps divided by the interface bandwidth: 100,000 kbps / 1,544 kbps ≈ 64.7, which IOS truncates to an integer cost of 64. The result is a whole number, never a fraction. Slow serial links therefore carry much higher OSPF costs than LAN interfaces.

A router has two equal-cost OSPF paths to the same destination, each with cost 20. Assuming default settings, how does the router use them?

• a.It keeps only the first path learned and stores the second as a floating backup route
• b.It combines the two links into a single logical EtherChannel and load-balances by MAC
• c.It installs both paths and load-balances traffic across them (equal-cost multipath)✓
• d.It picks the path whose next-hop router has the numerically higher router ID and ignores the other

OSPF installs multiple equal-cost paths (equal-cost multipath) up to the platform maximum, load-sharing traffic across them. Both cost-20 paths appear in the routing table with the same destination. If the costs differed, only the lower-cost path would be installed, since OSPF does not do unequal-cost load balancing.

During DR/BDR election on a broadcast OSPF network, which criterion is evaluated first?

• a.The highest OSPF interface priority✓
• b.The highest configured router ID on the segment
• c.The interface that came up earliest after the last reload
• d.The lowest IP address assigned to the interface

OSPF first compares interface priority, and the router with the highest priority becomes the DR. If priorities tie (the default is 1), the highest router ID breaks the tie. Setting an interface priority of 0 removes a router from the election entirely so it can never become DR or BDR.

What is the purpose of the Backup Designated Router (BDR) on an OSPF multiaccess segment?

• a.It monitors the DR and immediately takes over DR duties if the DR fails✓
• b.It performs the SPF calculation on behalf of all DROTHER routers to save their CPU
• c.It load-balances LSA flooding with the DR by handling exactly half of the neighbors
• d.It stores a second copy of every routed packet in case the DR drops one in transit

The BDR listens to all adjacencies and maintains synchronization with the DR so that if the DR fails, the BDR is promoted immediately without a full re-election delay. This provides fast, seamless recovery of the LSA-flooding role. A new BDR is then elected from the remaining routers on the segment.

On which OSPF interface priority setting will a router be prevented from ever becoming the DR or BDR?

• a.A priority of 1, which is the interface default
• b.A priority of 255, the maximum possible value
• c.A priority equal to the router's own numeric router ID
• d.A priority of 0✓

An OSPF interface priority of 0 makes the router ineligible for DR/BDR election, so it always remains a DROTHER on that segment. The highest priority wins the election, and 255 is the maximum. Priority is configured per interface, allowing precise control over which routers assume the DR role.

Which multicast address does OSPF use to send hello packets to all OSPF routers on a segment?

• a.224.0.0.9, the address reserved for RIP version 2 updates
• b.224.0.0.5✓
• c.255.255.255.255, the all-hosts limited broadcast address
• d.224.0.0.10, which is shared with EIGRP for neighbor discovery

OSPF hellos are sent to the AllSPFRouters multicast address 224.0.0.5, which every OSPF-speaking router listens on. The DR and BDR additionally use 224.0.0.6 (AllDRouters). EIGRP uses 224.0.0.10 and RIPv2 uses 224.0.0.9, so the addresses help identify the protocol in a capture.

By default, how often does OSPF send hello packets on a broadcast (Ethernet) network type?

• a.Every 120 seconds to minimize control-plane overhead
• b.Every 10 seconds✓
• c.Every 30 seconds, matching the default RIP update interval
• d.Every 40 seconds, which equals the dead interval

On broadcast and point-to-point OSPF networks the default hello interval is 10 seconds, and the dead interval is four times that, or 40 seconds. If a neighbor's hellos are missed for the full dead interval, the adjacency is torn down. Both timers must match between neighbors for an adjacency to form.

By default on a broadcast OSPF segment, after how many seconds without a hello will a router declare its neighbor down?

• a.20 seconds, which is twice the hello interval
• b.120 seconds, giving generous tolerance for transient link flaps
• c.10 seconds, equal to the hello interval itself
• d.40 seconds✓

The default OSPF dead interval on broadcast and point-to-point links is 40 seconds, which is four times the 10-second hello interval. Missing hellos for that entire period causes the neighbor to be declared down and the adjacency to drop. Lowering both timers speeds up failure detection at the cost of more control traffic.

Which command enables OSPF process 1 and advertises only the 10.1.1.0/24 network in area 0?

• a.router ospf 1 / network 10.1.1.0 0.0.0.255 area 0✓
• b.router ospf area 0 / network 10.1.1.0 0.0.0.255 process 1 with the process at the end
• c.router ospf 1 / network 10.1.1.0 255.255.255.0 area 0 using the subnet mask directly
• d.router ospf 1 / advertise 10.1.1.0/24 into area 0 with a single summary statement

OSPF network statements use a wildcard mask, not a subnet mask, so 10.1.1.0 0.0.0.255 correctly matches the /24. The area keyword places matched interfaces into area 0. The process ID (1 here) is only locally significant and need not match between routers.

An OSPF process is configured with 'network 0.0.0.0 255.255.255.255 area 0'. What does this achieve?

• a.It disables OSPF on every interface until specific networks are added individually
• b.It enables OSPF in area 0 on every interface that has an IP address✓
• c.It advertises only the 0.0.0.0/0 default route into the OSPF domain for all neighbors
• d.It creates a syntax error because the wildcard mask exceeds the allowed range

The wildcard 255.255.255.255 matches any IP address, so this single statement activates OSPF in area 0 on all interfaces that have an IP configured. It is a common shortcut in labs and small networks. Interfaces you do not want forming adjacencies should still be marked passive.

Which OSPF neighbor state occurs immediately after a router receives a hello but has not yet seen its own router ID listed in that hello?

• a.INIT✓
• b.FULL
• c.EXCHANGE, during which the two routers swap database description packets
• d.LOADING, where link-state requests are sent for missing entries

The INIT state means a router has received a hello from a neighbor but has not yet seen its own router ID echoed back, so bidirectional communication is not confirmed. Once each side sees the other in its hellos, they move to 2-WAY. EXCHANGE and LOADING occur later, after adjacency is agreed upon.

In OSPF, which neighbor state confirms that bidirectional communication has been established between two routers?

• a.INIT, reached as soon as any hello arrives on the interface
• b.2-WAY✓
• c.ATTEMPT, used when unicasting hellos to a manually defined neighbor
• d.EXSTART, where the master/slave relationship for the exchange is negotiated

The 2-WAY state is reached when a router sees its own router ID in a neighbor's hello, confirming two-way communication. On multiaccess links, DR/BDR election happens at this point, and DROTHER routers stay 2-WAY with each other. Routers that will become fully adjacent then proceed to EXSTART.

OSPF neighbors are stuck in the EXSTART/EXCHANGE state and never reach FULL. Which mismatch most commonly causes this specific symptom?

• a.One router is using OSPFv2 while the other is using OSPFv3 on the shared link
• b.The interface MTU values do not match on the two ends of the link✓
• c.The administrative distance for OSPF has been changed on only one of the routers
• d.The two routers are configured with different OSPF process IDs on their interfaces

A mismatched interface MTU is the classic cause of OSPF neighbors hanging in EXSTART/EXCHANGE, because database description packets fail to be processed. The process ID is only locally significant and never affects adjacency. Ensuring identical MTU on both interfaces resolves the stuck state.

What is the primary function of the OSPF router ID?

• a.It selects which physical interface will be used as the default gateway
• b.It sets the administrative distance the router advertises to its neighbors
• c.It determines the OSPF cost of every interface on the router at startup
• d.It uniquely identifies the router within the OSPF domain✓

The router ID is a 32-bit value, formatted like an IPv4 address, that uniquely identifies each router in the OSPF domain and appears in LSAs. It is chosen from an explicit router-id command, then the highest loopback, then the highest active interface IP. Duplicate router IDs cause adjacency and routing problems.

Why is a loopback interface commonly used to set the OSPF router ID?

• a.A loopback disables DR/BDR election on all connected multiaccess segments
• b.A loopback forces OSPF to use hop count instead of bandwidth for its metric
• c.A loopback never goes down as long as the router is up, giving a stable router ID✓
• d.A loopback automatically receives the lowest possible IP and wins DR elections It also forces the interface priority to zero so the router never becomes a DR.

Loopback interfaces are virtual and remain up as long as the router is operational, so tying the router ID to a loopback keeps it stable even if physical links flap. OSPF prefers the highest loopback IP over physical interfaces when no router-id is explicitly set. Best practice is still to configure the router-id manually.

After changing the OSPF router ID with the 'router-id' command, what must occur for the new ID to take effect?

• a.Nothing; OSPF applies the new router ID to existing adjacencies immediately and transparently Until that recalculation finishes, all neighbor adjacencies remain in the INIT state.
• b.The reference bandwidth must be recalculated to match the new router ID value
• c.The OSPF process must be cleared or the router reloaded so adjacencies rebuild with the new ID✓
• d.All interfaces must be shut and reopened before the router ID value is recognized

OSPF does not change an already-running router ID on the fly. You must clear the OSPF process with 'clear ip ospf process' (or reload) so the new router ID is adopted and adjacencies are rebuilt. Until then, the previously selected router ID stays in effect.

Which type of OSPF network, by default, elects a DR and BDR?

• a.Point-to-multipoint interfaces configured on a hub-and-spoke Frame Relay cloud
• b.Loopback interfaces advertised as host routes into the OSPF domain
• c.Point-to-point serial links between exactly two routers
• d.Broadcast multiaccess networks such as Ethernet LAN segments✓

Broadcast multiaccess networks like Ethernet elect a DR and BDR to reduce the number of full adjacencies and control LSA flooding. Point-to-point and point-to-multipoint types have no DR/BDR because there is no benefit with only paired neighbors. Matching network types on both ends is required for adjacency.

An administrator wants a static route to remain in the table only while its exit interface is up, without specifying a next hop. On a point-to-point serial link, which command form is appropriate?

• a.ip route 192.168.4.0 255.255.255.0 next-hop-self serial0/0/0
• b.ip route 192.168.4.0 255.255.255.0 serial0/0/0✓
• c.ip route 192.168.4.0 0.0.0.255 track serial0/0/0 for the interface state
• d.ip route 192.168.4.0 255.255.255.0 permanent broadcast on serial0/0/0

On a point-to-point link you can specify only the exit interface, and the route is valid while that interface is up/up. Because the link is point-to-point, there is no ambiguity about the next hop. This avoids the recursive ARP concerns that arise when using an exit interface on multiaccess Ethernet.

What is a recursive static route?

• a.A static route that automatically re-advertises itself to every OSPF neighbor each interval Such routes are stored separately from the main table and never age out on their own.
• b.A static route whose next-hop IP must itself be resolved through another routing-table lookup✓
• c.A static route that points to two next hops simultaneously for redundancy
• d.A static route configured with a wildcard mask instead of a subnet mask

A recursive static route specifies only a next-hop IP address, so the router must perform a second lookup to find how to reach that next hop before it can forward. If the next hop cannot be resolved, the route is not installed. Specifying an exit interface (a fully specified route) avoids the recursive lookup.

A host route appears in a Cisco routing table. Which prefix length identifies an IPv4 host route?

• a./30, which is used for point-to-point links between two routers
• b./32✓
• c./24, the standard length for a class C sized network segment
• d./28, providing a small block of sixteen addresses

An IPv4 host route uses a /32 prefix (mask 255.255.255.255), identifying a single specific address rather than a network. Local interface addresses show up as /32 'L' entries, and loopbacks are commonly advertised as host routes. A /30 or /28 describes a range of addresses, not a single host.

In 'show ip route', what does the 'L' code preceding an entry indicate?

• a.A local /32 route for an address configured on one of the router's own interfaces✓
• b.A summarized route created by manual route aggregation on the interface
• c.A route learned from the LACP link-aggregation control protocol
• d.A route that is currently in a loading state and not yet usable for forwarding These entries are removed automatically whenever an EtherChannel bundle renegotiates.

The 'L' code marks a local route, a /32 host entry automatically created for each IP address configured on the router's own interfaces. It sits alongside the 'C' (connected) network route for the same interface. These local routes ensure traffic destined to the router itself is handled correctly.

A packet arrives for 203.0.113.200 and the routing table contains no matching route and no default route. What does the router do?

• a.It forwards the packet to the interface with the highest configured IP address
• b.It floods the packet out every interface hoping a downstream router can deliver it
• c.It drops the packet and may send an ICMP destination-unreachable message✓
• d.It buffers the packet and periodically retries until a matching route is learned

When no route (including no default route) matches a packet's destination, the router discards it as unroutable. It typically returns an ICMP 'destination network unreachable' message to the source. This is why a gateway of last resort is configured on edge routers to catch otherwise-unmatched traffic.

Which statement best describes the 'gateway of last resort'?

• a.The MAC address a host uses to reach devices on its own local subnet
• b.The interface with the lowest OSPF cost on the entire router
• c.The next hop used for any destination that does not match a more specific route✓
• d.A backup router that assumes all forwarding when the primary router fails This interface is chosen fresh after every SPF run and can change without warning.

The gateway of last resort is the next hop associated with the default route (0.0.0.0/0), used when no more specific prefix matches a packet. It is displayed at the top of 'show ip route'. Without it, unmatched traffic is dropped, so edge routers almost always define one toward the ISP.

How does a Layer 3 switch differ from a traditional Layer 2 switch in terms of routing?

• a.A Layer 3 switch can route between VLANs using switched virtual interfaces (SVIs)✓
• b.A Layer 3 switch can only forward frames and must send all inter-VLAN traffic to a router
• c.A Layer 3 switch forwards packets purely in software, making it slower than a router
• d.A Layer 3 switch replaces every router in the network and cannot perform switching

A Layer 3 switch adds routing capability, allowing it to route between VLANs using SVIs or routed ports at hardware speed. This eliminates the traffic bottleneck of the older 'router-on-a-stick' approach for inter-VLAN routing. It still performs normal Layer 2 switching within each VLAN.

To enable inter-VLAN routing on a multilayer switch, which command must be issued in global configuration mode?

• a.ip routing✓
• b.spanning-tree vlan routing enable across the affected VLAN range
• c.no switchport followed by ip default-gateway on the VLAN interface
• d.switchport mode trunk on every access port carrying user VLANs

The global command 'ip routing' enables IPv4 routing on a multilayer switch so its SVIs can forward traffic between VLANs. Without it, the switch behaves purely at Layer 2 and SVIs serve only as management interfaces. Each participating VLAN then needs an SVI with an IP address acting as the gateway.

In a 'router-on-a-stick' configuration, how are the router's subinterfaces associated with VLANs?

• a.The router negotiates VLAN membership dynamically using VTP with the switch
• b.Each subinterface is configured with 'encapsulation dot1Q <vlan-id>' and an IP address✓
• c.Subinterfaces inherit VLAN IDs automatically from the connected switch's database The switch then prunes any VLAN that the router has not explicitly requested to carry.
• d.Each subinterface is placed into access mode with a single switchport command

With router-on-a-stick, a single physical link is a trunk, and each subinterface uses 'encapsulation dot1Q <vlan-id>' plus an IP address to serve as the gateway for that VLAN. The router tags and untags frames according to those subinterface settings. This lets one router route among many VLANs over one physical connection.

What is the effect of configuring an IP address directly on a Layer 3 routed port using the 'no switchport' command?

• a.The port stops participating in VLANs and becomes a routed interface like a router port✓
• b.The port is added to VLAN 1 and begins forwarding untagged frames only
• c.The port becomes a trunk carrying all VLANs to the connected router
• d.The port is administratively disabled until an SVI is created for it

Issuing 'no switchport' converts a switch port from a Layer 2 interface into a Layer 3 routed port that behaves like a router interface, letting you assign it an IP address. It no longer belongs to any VLAN. Routed ports are common on uplinks between multilayer switches where a full VLAN is unnecessary.

Which of these best describes the difference between an interior gateway protocol (IGP) and an exterior gateway protocol (EGP)?

• a.IGPs route within a single autonomous system, while EGPs (like BGP) route between autonomous systems✓
• b.IGPs are always static, while EGPs are always learned dynamically from neighbors
• c.IGPs use TCP for reliability, while EGPs rely on unacknowledged broadcasts
• d.IGPs run only on switches, while EGPs run only on routers at the network edge

IGPs such as OSPF, EIGRP, and RIP exchange routes within a single autonomous system. EGPs, notably BGP, exchange reachability between different autonomous systems and form the backbone of Internet routing. The distinction is about scope, not about which device type runs them.

A summary route 172.16.0.0/22 is advertised. Which of the following networks is NOT included in that summary?

• a.172.16.3.0/24, the last /24 contained in the summary
• b.172.16.2.0/24, another subnet inside the aggregate range
• c.172.16.1.0/24, which falls within the summarized block
• d.172.16.4.0/24✓

A /22 summary starting at 172.16.0.0 spans the third octet from 0 through 3 (a block of four), covering 172.16.0.0 to 172.16.3.255. Therefore 172.16.4.0/24 lies outside the aggregate. Route summarization reduces routing-table size by advertising contiguous subnets as one entry.

What is the main benefit of route summarization (aggregation) in a large routed network?

• a.It guarantees equal-cost load balancing across all summarized paths automatically
• b.It encrypts routing updates so that summarized prefixes cannot be intercepted
• c.It increases the administrative distance of every summarized route for security
• d.It reduces routing-table size and hides individual link flaps behind the summary✓

Summarization advertises many contiguous subnets as a single aggregate prefix, shrinking routing tables and lowering memory and CPU use. It also contains instability, because a flap of one specific subnet does not trigger updates for the summary. Effective summarization depends on a hierarchical, contiguous addressing plan.

Which address correctly summarizes the four networks 10.0.0.0/24, 10.0.1.0/24, 10.0.2.0/24, and 10.0.3.0/24?

• a.10.0.0.0/22✓
• b.10.0.0.0/24, identical to just the first subnet in the group
• c.10.0.0.0/21, which is broader than necessary and includes extra networks
• d.10.0.0.0/23, which only covers the first two of the four subnets

Four contiguous /24s combine into a single /22, because summarizing four networks removes two bits of specificity (2^2 = 4). 10.0.0.0/22 covers 10.0.0.0 through 10.0.3.255 exactly. A /23 would cover only two of the four, and a /21 would cover eight networks, more than needed.

Why does OSPF prefer intra-area routes over inter-area routes to the same destination when both exist?

• a.Because inter-area routes are filtered out entirely by the backbone area 0
• b.Because intra-area routes are static while inter-area routes are dynamic
• c.Because OSPF path preference favors intra-area (O) over inter-area (O IA) routes regardless of cost✓
• d.Because inter-area routes always have a higher administrative distance than intra-area routes Because of this, the backbone area silently discards the less specific of the two.

OSPF applies a route-type preference order in which intra-area (O) routes are chosen over inter-area (O IA) routes to the same prefix, even if the inter-area path has a lower cost. Below those come external type 1 and then type 2 routes. The administrative distance is 110 for all standard OSPF routes, so it is the route type, not AD, that decides here.

What does an OSPF Type 1 (Router) LSA describe?

• a.A summary of networks from one area advertised into another area by an ABR
• b.The identity of the DR and the multiaccess network it represents to the area
• c.The complete list of external routes redistributed into OSPF from other protocols
• d.A router's own directly connected links and their states within its area✓

A Type 1 Router LSA is generated by every OSPF router to describe its own directly connected links, their cost, and their state within an area. These LSAs are flooded throughout the area but not beyond it. Type 2 LSAs describe multiaccess networks, Type 3 carry inter-area summaries, and Type 5 carry external routes.

Which OSPF router role connects one area to the backbone area 0 and generates Type 3 summary LSAs?

• a.Internal router, which has all interfaces within a single non-backbone area
• b.Area Border Router (ABR)✓
• c.Designated Router (DR), elected on each broadcast segment in the area
• d.Autonomous System Boundary Router (ASBR), which redistributes external routes

An Area Border Router has interfaces in two or more areas, including area 0, and generates Type 3 summary LSAs to advertise networks between areas. An ASBR, by contrast, injects external routes via Type 5 LSAs. The ABR is the boundary through which all inter-area traffic and summaries pass.

Which command displays the OSPF neighbor table, including neighbor state and DR/BDR roles?

• a.show ip ospf neighbor✓
• b.show ip protocols, summarizing configured routing processes only
• c.show ip ospf database, which dumps the full link-state database
• d.show ip route ospf, which lists only installed OSPF routes

'show ip ospf neighbor' lists each neighbor's router ID, state (for example FULL/DR), priority, dead-timer, and interface. It is the primary tool for verifying adjacencies. 'show ip ospf database' shows the LSDB contents, and 'show ip route ospf' shows only the resulting installed routes.

A router receives the same 192.168.50.0/24 prefix from OSPF (AD 110) and RIP (AD 120). Which is installed, and where does the other go?

• a.Both install and the router alternates between them on every other packet
• b.Neither installs until the administrator manually chooses a preferred protocol This alternation continues until one of the two protocols is administratively shut down.
• c.The OSPF route installs due to its lower AD; the RIP route stays only in RIP's database✓
• d.The RIP route installs because RIP is simpler, and OSPF is discarded entirely

Administrative distance breaks the tie between protocols advertising identical prefixes: OSPF's AD of 110 beats RIP's 120, so the OSPF route is installed in the routing table. The RIP route is retained inside RIP's own database and would install only if the OSPF route disappeared. Lower AD always wins for the same prefix.

What is the default administrative distance of a route learned via RIP?

• a.90, matching internal EIGRP routes
• b.1, which is reserved for static routes
• c.120✓
• d.110, the same value that OSPF uses by default

RIP routes have a default administrative distance of 120, making RIP less preferred than OSPF (110) and EIGRP (90) when the same prefix is available from multiple protocols. Directly connected routes are 0 and static routes are 1. Knowing default AD values is essential for predicting which route a router installs.

Which metric does RIP use to select the best path to a destination?

• a.Cumulative bandwidth of all links along the path, expressed as OSPF-style cost
• b.A composite of bandwidth and delay similar to the EIGRP calculation
• c.Hop count✓
• d.Reference bandwidth divided by the slowest interface bandwidth on the path

RIP uses hop count as its sole metric, preferring the path with the fewest routers to cross, with a maximum of 15 hops (16 is unreachable). This simplicity ignores link bandwidth, so RIP may choose a slow path with fewer hops over a fast path with more. OSPF and EIGRP use bandwidth-based metrics instead.

In RIP, what does a route advertised with a hop count of 16 signify?

• a.The destination is unreachable (infinity)✓
• b.The destination is exactly 16 routers away but still reachable
• c.The route is a summarized aggregate covering sixteen subnets
• d.The route has the highest priority and should be installed immediately

RIP treats a hop count of 16 as infinity, meaning the network is unreachable, since the protocol's maximum valid hop count is 15. Advertising 16 is how RIP poisons a route to signal that it is no longer usable. This small diameter limits RIP to relatively compact networks.

An engineer needs the router to display how a specific destination, 172.20.5.9, would be forwarded, including the matched route and next hop. Which command is most direct?

• a.show running-config | include 172.20.5.9 to grep the configuration
• b.show ip cef exact-route only, which omits the administrative distance
• c.show ip route summary, which totals the number of routes by type
• d.show ip route 172.20.5.9✓

'show ip route <ip-address>' performs a routing-table lookup for that specific address and displays the matching route, its prefix length, metric, and next hop. This is faster than scanning the whole table when troubleshooting a single destination. It reflects the actual longest-prefix-match decision the router would make.

What is 'next-hop' in the context of IP routing?

• a.The IP address of the adjacent router to which a packet is forwarded on its way to the destination✓
• b.The originating router that first generated the packet onto the network This loopback address is also what neighboring routers use as the packet's next hop.
• c.The loopback address a router uses to identify itself within OSPF
• d.The final destination host to which the packet is ultimately addressed

The next hop is the IP address of the immediately adjacent router that a device forwards a packet to on the path toward its final destination. Routing tables map destination prefixes to next-hop addresses (or exit interfaces). The forwarding device resolves the next hop's MAC via ARP to build the Layer 2 frame.

Two static routes to 10.9.0.0/16 exist: one via 10.0.0.1 with default AD, and one via 10.0.0.2 configured as 'ip route 10.9.0.0 255.255.0.0 10.0.0.2 5'. Which is preferred?

• a.Both are used simultaneously since static routes always load-balance by default
• b.The route via 10.0.0.1, because its default AD of 1 is lower than 5✓
• c.Neither, because two static routes to the same prefix cancel each other out
• d.The route via 10.0.0.2 because a higher AD indicates a more trusted manual entry

The first static route uses the default administrative distance of 1, while the second is explicitly set to 5, making it a floating backup. The lower AD (1) via 10.0.0.1 is preferred and installed. The route via 10.0.0.2 installs only if the primary route's next hop becomes unreachable.

Which statement about equal-cost load balancing on a Cisco router is correct?

• a.Only static routes can be load-balanced; dynamic protocols always pick a single path
• b.By default the router can install multiple equal-metric paths and share traffic across them✓
• c.Load balancing requires all paths to use the same routing protocol and the same interface type
• d.Load balancing is disabled unless an EtherChannel bundles the physical links first

When a routing protocol produces several paths with the same metric to a destination, the router installs them all (up to the maximum-paths limit) and balances traffic across them. This works for OSPF, EIGRP, and even multiple equal-AD static routes. Per-destination balancing is the default, preserving packet order per flow.

A default route is redistributed into OSPF using the 'default-information originate' command. What does this do?

• a.It advertises the router's existing default route to all other OSPF routers in the domain✓
• b.It removes the default route from the local table to prevent routing loops
• c.It forces every OSPF router to generate its own independent default route locally Each router then withdraws its own default route to prevent a forwarding loop forming.
• d.It changes the OSPF administrative distance of the default route to zero

'default-information originate' tells an OSPF router (typically the one with an Internet-facing default route) to advertise a default route to the rest of the OSPF domain. Other routers then learn 0.0.0.0/0 as an OSPF external route pointing toward the edge. This centralizes default routing at the network border.

What does the 'O E2' code mean in a Cisco routing table?

• a.An OSPF route currently being recalculated by the SPF algorithm
• b.An intra-area OSPF route with an unusually high accumulated cost
• c.An OSPF external Type 2 route, whose metric reflects only the external cost✓
• d.An OSPF route that has been manually summarized by an area border router During this recalculation the route is held in a pending state and cannot forward traffic.

'O E2' marks an OSPF external Type 2 route, typically redistributed into OSPF from another source by an ASBR. For E2 routes the metric equals the external cost only and does not increase as the route propagates through the OSPF domain. E1 routes, by contrast, add internal cost to the external metric.

Which OSPF concept prevents a single router failure from forcing every other router to recompute all routes for unrelated areas?

• a.Hold-down timers that freeze route changes for a fixed period after a failure
• b.Dividing the network into multiple areas so SPF recalculation stays localized✓
• c.Split horizon, which stops a router from advertising a route back where it came from
• d.Poison reverse, which advertises failed routes with an infinite metric

OSPF's multi-area design confines detailed topology (Type 1/2 LSAs) to within each area, so a link change triggers full SPF recalculation only inside the affected area. Other areas see only summary changes, if any. This scoping keeps large OSPF domains stable and reduces CPU load compared with a single flat area.