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Aruba Switching Professional practice questions

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Question 1Wired and wireless network fundamentals (routing/switching)

Which OSI layer is responsible for logical addressing and path selection between networks?

  1. Session layer
  2. Transport layer
  3. Data link layer
  4. Network layer Correct answer.

Explanation

The network layer handles logical addressing (such as IP addresses) and determines how packets are forwarded between networks. Path selection and routing decisions occur at this layer.

Question 2Wired and wireless network fundamentals (routing/switching)

What is the primary function of ARP on an Ethernet network?

  1. Translate domain names into IP addresses
  2. Assign IP addresses to hosts dynamically
  3. Map a MAC address to a VLAN identifier
  4. Resolve an IP address to a MAC address Correct answer.

Explanation

ARP broadcasts a request asking which device owns a given IP address, and the owner replies with its MAC address. This lets a host build the frame with the correct destination hardware address.

Question 3Wired and wireless network fundamentals (routing/switching)

A switch receives a frame with a destination MAC address that is not present in its MAC address table. How does the switch handle the frame?

  1. It holds the frame until the destination replies
  2. It forwards the frame only to the default gateway port
  3. It forwards the frame out every port except the ingress port Correct answer.
  4. It discards the frame and sends an ICMP error

Explanation

When the destination MAC is unknown, a switch performs flooding, sending the frame out all ports in the same VLAN except the one it arrived on. The reply then populates the MAC table.

Question 4Wired and wireless network fundamentals (routing/switching)

Which statement describes a VLAN?

  1. A tunnel that encrypts traffic between two sites
  2. A routing protocol that exchanges prefixes between switches
  3. A physical segment shared by all switches in a stack
  4. A logical grouping of ports that forms a separate broadcast domain Correct answer.

Explanation

A VLAN partitions a switch into multiple logical broadcast domains, so broadcasts stay within the VLAN. Ports in different VLANs require Layer 3 forwarding to communicate.

Question 5Wired and wireless network fundamentals (routing/switching)

What is the purpose of the 802.1Q tag in an Ethernet frame?

  1. It marks the frame priority for QoS only
  2. It identifies the VLAN to which the frame belongs Correct answer.
  3. It carries the source IP address for routing
  4. It authenticates the sender to the switch

Explanation

The 802.1Q tag inserts a VLAN identifier into the Ethernet header so switches can carry multiple VLANs over a shared trunk link. It also includes a priority field, but its primary role is VLAN identification.

Question 6Wired and wireless network fundamentals (routing/switching)

On a trunk link between two switches, how are frames for the native VLAN typically handled?

  1. They are dropped at the trunk boundary
  2. They are double-tagged with two VLAN IDs
  3. They are sent untagged on the link Correct answer.
  4. They are sent tagged with VLAN 1 always

Explanation

By default, frames belonging to the native VLAN traverse a trunk untagged, while other VLANs are tagged. Both ends of the trunk must agree on the native VLAN to avoid misforwarding.

Question 7Wired and wireless network fundamentals (routing/switching)

Which Spanning Tree Protocol port state forwards user traffic and learns MAC addresses?

  1. Listening
  2. Blocking
  3. Learning
  4. Forwarding Correct answer.

Explanation

In the forwarding state a port both learns MAC addresses and forwards user traffic. The learning state builds the MAC table but does not yet forward user frames.

Question 8Wired and wireless network fundamentals (routing/switching)

What is the purpose of the root bridge election in Spanning Tree Protocol?

  1. To balance traffic equally across all redundant links
  2. To choose the port with the highest path cost as the designated port
  3. To select the switch with the lowest bridge ID as the topology reference point Correct answer.
  4. To assign IP addresses to switches in the topology

Explanation

Switches exchange BPDUs and the one with the lowest bridge ID (priority plus MAC) becomes the root. All switches then compute loop-free paths toward that root.

Question 9Wired and wireless network fundamentals (routing/switching)

A switch port configured as an edge (PortFast) port is connected to an end-user workstation. What is the effect of this configuration?

  1. The port becomes a trunk automatically
  2. The port skips listening and learning and moves directly to forwarding Correct answer.
  3. The port is excluded from the spanning tree entirely
  4. The port blocks all broadcast traffic

Explanation

An edge port transitions immediately to forwarding so end devices can communicate without waiting through STP timers. It should only be used where no switch or bridge is connected.

Question 10Wired and wireless network fundamentals (routing/switching)

Which protocol provides link aggregation by combining multiple physical links into one logical link?

  1. LLDP
  2. VRRP
  3. STP
  4. LACP Correct answer.

Explanation

LACP (IEEE 802.3ad) negotiates and maintains link aggregation groups so multiple physical links act as one logical link. This increases bandwidth and provides redundancy.

Question 11Wired and wireless network fundamentals (routing/switching)

What does a router do with a packet whose destination network is not in its routing table and no default route exists?

  1. It drops the packet Correct answer.
  2. It forwards the packet to the lowest-cost neighbor
  3. It floods the packet on all interfaces
  4. It converts the packet to a broadcast

Explanation

Without a matching route or default route, the router has no path and discards the packet. It typically returns an unreachable message to the source.

Question 12Wired and wireless network fundamentals (routing/switching)

Which characteristic distinguishes a distance-vector routing protocol from a link-state protocol?

  1. Distance-vector routers share their full routing tables with neighbors Correct answer.
  2. Distance-vector protocols require a hierarchical area design
  3. Distance-vector protocols use Dijkstra's algorithm
  4. Distance-vector routers build a complete topology map of the network

Explanation

Distance-vector protocols advertise routes and metrics to directly connected neighbors, which then propagate them. Link-state protocols instead flood link information so each router builds a full topology map.

Question 13Wired and wireless network fundamentals (routing/switching)

Which routing table entry is used when a router has multiple routes to the same destination prefix with equal administrative distance but different metrics?

  1. The route learned most recently
  2. The route with the oldest timestamp
  3. The route with the lowest metric Correct answer.
  4. The route with the highest metric

Explanation

Administrative distance is compared first; if routes share the same distance, the lower metric is preferred. Equal distance and metric may allow load balancing depending on the platform.

Question 14Wired and wireless network fundamentals (routing/switching)

What is the function of a default gateway on a host?

  1. It assigns the host its IP address
  2. It filters broadcast traffic on the local segment
  3. It provides a next hop for traffic destined outside the local subnet Correct answer.
  4. It resolves hostnames to IP addresses

Explanation

When a host determines the destination is not on its local subnet, it sends the frame to the default gateway, which routes it onward. The gateway must be reachable on the local subnet.

Question 15Wired and wireless network fundamentals (routing/switching)

A host with IP 192.168.10.50 and mask 255.255.255.0 wants to reach 192.168.11.20. What does the host do?

  1. It broadcasts an ARP request for 192.168.11.20 on the local segment
  2. It sends the frame to its default gateway's MAC address Correct answer.
  3. It sends the frame directly to 192.168.11.20's MAC address
  4. It drops the packet because the destination is unreachable

Explanation

The destination is on a different subnet, so the host forwards the frame to its default gateway. It uses ARP to resolve the gateway's MAC, not the remote host's.

Question 16Wired and wireless network fundamentals (routing/switching)

Which address range is reserved for private use under RFC 1918?

  1. 169.254.0.0 to 169.254.255.255
  2. 224.0.0.0 to 239.255.255.255
  3. 172.16.0.0 to 172.31.255.255 Correct answer.
  4. 192.0.2.0 to 192.0.2.255

Explanation

RFC 1918 defines 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 as private ranges. The 172.16.0.0 to 172.31.255.255 block is the /12 private range.

Question 17Wired and wireless network fundamentals (routing/switching)

How many usable host addresses are available in a subnet with a /27 prefix?

  1. 62
  2. 14
  3. 30 Correct answer.
  4. 32

Explanation

A /27 leaves 5 host bits, giving 2^5 = 32 addresses. Subtracting the network and broadcast addresses leaves 30 usable host addresses.

Question 18Wired and wireless network fundamentals (routing/switching)

Which statement about a Layer 3 switch is accurate?

  1. It operates only in the data link layer
  2. It forwards frames using only MAC addresses
  3. It can route packets between VLANs using switched virtual interfaces Correct answer.
  4. It cannot participate in dynamic routing protocols

Explanation

A Layer 3 switch combines switching and routing, using switched virtual interfaces to route between VLANs. This avoids sending inter-VLAN traffic through an external router.

Question 19Wired and wireless network fundamentals (routing/switching)

What is the role of DHCP relay on a router?

  1. It acts as a backup DHCP server for the local subnet
  2. It assigns static addresses to DHCP clients
  3. It forwards DHCP requests from a subnet to a DHCP server on another subnet Correct answer.
  4. It encrypts DHCP messages between client and server

Explanation

Because DHCP broadcasts do not cross routers, a relay agent forwards client requests to a remote DHCP server and returns the replies. This lets one server serve many subnets.

Question 20Wired and wireless network fundamentals (routing/switching)

Which protocol provides first-hop redundancy by allowing multiple routers to share a virtual IP address?

  1. VRRP Correct answer.
  2. OSPF
  3. LLDP
  4. LACP

Explanation

VRRP lets a group of routers share a virtual IP and MAC so hosts keep a consistent gateway if the master fails. VRRP is an open standard for gateway redundancy.

Question 21Wired and wireless network fundamentals (routing/switching)

How does a wireless access point operating in infrastructure mode differ from an ad hoc network?

  1. The access point requires a wired backhaul to every client
  2. The network operates without any radio channels
  3. Clients communicate through the access point rather than directly with each other Correct answer.
  4. Clients always communicate directly with each other

Explanation

In infrastructure mode, all client traffic passes through the access point, which manages the basic service set. Ad hoc mode lets clients communicate directly without an access point.

Question 22Wired and wireless network fundamentals (routing/switching)

Which statement best describes a broadcast domain?

  1. The set of devices reachable through a single router interface only
  2. The set of devices sharing the same IP subnet mask length
  3. The set of switch ports configured with the same speed
  4. The set of devices that receive a broadcast frame sent by any member Correct answer.

Explanation

A broadcast domain includes all devices that receive a broadcast frame; switches forward broadcasts within a VLAN. Routers (and VLAN boundaries) separate broadcast domains.

Question 23Wired and wireless network fundamentals (routing/switching)

A network engineer observes that a switch port connected to a workstation is flapping between up and down. Which cause is most likely?

  1. A duplex mismatch on the link Correct answer.
  2. A duplicate IP address on the workstation
  3. An incorrect default gateway on the workstation
  4. A missing VLAN on the trunk

Explanation

A duplex mismatch causes collisions, late collisions, and CRC errors that can make the link unstable and cause it to flap. Duplicate IP or gateway errors affect connectivity but not physical link state.

Question 24Wired and wireless network fundamentals (routing/switching)

Why can a Layer 2 loop form between two switches connected by two links without STP?

  1. The links negotiate different duplex settings
  2. The switches use different MAC address formats
  3. Broadcast frames are flooded endlessly because there is no TTL field in Ethernet Correct answer.
  4. Ethernet frames include a TTL that expires too slowly

Explanation

Ethernet frames have no TTL, so flooded broadcasts circulate forever around a loop. This causes broadcast storms and MAC table instability until STP blocks a redundant link.

Question 25Wired and wireless network fundamentals (routing/switching)

Two OSPF routers on the same broadcast segment are stuck in the ExStart state. Which issue is the most likely cause?

  1. A different router priority value
  2. An MTU mismatch between the interfaces Correct answer.
  3. A mismatched OSPF process ID
  4. A missing default route

Explanation

During database exchange, OSPF negotiates the master/slave relationship and packet size; an MTU mismatch prevents the exchange from progressing beyond ExStart. Process IDs are locally significant and priorities affect DR election only.

Question 26Wired and wireless network fundamentals (routing/switching)

Which mechanism prevents frames from being duplicated when a switch receives a broadcast frame on multiple ports in the same VLAN?

  1. The switch forwards broadcasts only toward the root port of the VLAN
  2. The switch forwards a broadcast out of all ports in the VLAN except the ingress port Correct answer.
  3. The switch drops broadcasts unless IGMP snooping is enabled
  4. The MAC address table is flooded on every port once per second

Explanation

A broadcast frame must reach every host in the broadcast domain, so a switch floods it out of every port in the VLAN except the one it arrived on. This flooding behavior is the reason a redundant Layer 2 topology needs a loop-prevention protocol.

Question 27Wired and wireless network fundamentals (routing/switching)

Which statement describes how a VLAN tag is carried across an 802.1Q trunk link?

  1. The entire original frame is encapsulated inside a new tagged Ethernet frame
  2. A 4-byte tag is inserted in the Ethernet header that carries the VLAN identifier Correct answer.
  3. The VLAN identifier is written into the destination MAC address field
  4. A 12-byte shim is appended after the frame check sequence

Explanation

802.1Q inserts a 4-byte tag between the source MAC address and the EtherType field, and the tag includes a 12-bit VLAN ID. The original frame is otherwise unchanged and the FCS is recalculated.

Question 28Wired and wireless network fundamentals (routing/switching)

What is the effect of configuring a switch port as an access port in VLAN 20?

  1. The port accepts only tagged frames carrying VLAN 20
  2. The port becomes a member of all VLANs defined on the switch
  3. Frames leave the port tagged with VLAN 20 for any attached device
  4. The port places untagged traffic from the attached device into VLAN 20 Correct answer.

Explanation

An access port belongs to a single VLAN and treats untagged frames from the attached device as members of that VLAN. Frames sent to the device are transmitted untagged.

Question 29Wired and wireless network fundamentals (routing/switching)

A host on VLAN 10 needs to communicate with a host on VLAN 20. Both VLANs are configured on the same Layer 2 switch. What is required for this communication to succeed?

  1. A larger MAC address table on the switch
  2. Spanning Tree disabled on both VLANs
  3. An 802.1Q trunk between the two hosts
  4. A Layer 3 device with an interface in each VLAN to route between them Correct answer.

Explanation

VLANs are separate broadcast domains, so traffic between them must be routed by a Layer 3 device such as a router or Layer 3 switch with an interface in each VLAN. Layer 2 switching alone cannot move traffic between VLANs.

Question 30Wired and wireless network fundamentals (routing/switching)

A network uses 10.0.0.0/8 internally and must summarize it into a single route advertised to a neighbor. Which prefix represents that summary?

  1. 10.0.0.0/8 Correct answer.
  2. 10.0.0.0/30
  3. 10.0.0.0/16
  4. 10.0.0.0/24

Explanation

A summary route uses the shortest prefix that still encompasses all the addresses being advertised. Since the entire 10.0.0.0/8 block is in use, the /8 prefix is the correct summary.

Question 31Wired and wireless network fundamentals (routing/switching)

A router has two routes to 172.16.5.0/24: one learned via OSPF with metric 20 and one learned via RIP with metric 3. Which route is installed in the routing table?

  1. Both routes, with load balancing across them
  2. Neither route until a tie-breaker is configured manually
  3. The OSPF route because OSPF has a lower administrative distance Correct answer.
  4. The RIP route because its metric is numerically lower

Explanation

When different routing protocols offer a route to the same prefix, administrative distance is compared before metrics. OSPF's default administrative distance is lower than RIP's, so the OSPF route is preferred.

Question 32Wired and wireless network fundamentals (routing/switching)

Which field in an IPv4 header prevents a packet from circulating indefinitely when a routing loop exists?

  1. The Time to Live field, which is decremented at each hop Correct answer.
  2. The Header Checksum field, which is recalculated at each hop
  3. The Fragment Offset field, which tracks packet reassembly
  4. The Protocol field, which identifies the upper-layer protocol

Explanation

Each router decrements the TTL, and when it reaches zero the packet is discarded and an ICMP Time Exceeded message is returned. This bounds the lifetime of a packet caught in a loop.

Question 33Wired and wireless network fundamentals (routing/switching)

A wireless client associates to an access point and receives an address from the wired DHCP server. Which device function makes this possible when the AP is in bridge mode?

  1. The AP assigns addresses from a local pool and proxies them to the server
  2. The AP performs NAT between the wireless and wired segments
  3. The AP forwards the client's DHCP frames onto the wired VLAN as a Layer 2 bridge Correct answer.
  4. The AP acts as a DHCP relay agent to unicast requests to the server

Explanation

In bridge mode the AP is a Layer 2 device, so client broadcast frames such as DHCP Discover are bridged onto the wired VLAN where the server can answer. No Layer 3 relay function is performed by the AP in this mode.

Question 34Wired and wireless network fundamentals (routing/switching)

Which statement correctly compares a routed port on a multilayer switch with a switched virtual interface (SVI)?

  1. A routed port requires an access VLAN, while an SVI is always untagged
  2. A routed port and an SVI are functionally identical in all respects
  3. A routed port is a physical interface with an IP address and no VLAN membership, while an SVI is a logical interface tied to a VLAN Correct answer.
  4. A routed port carries all VLANs as a trunk, while an SVI carries a single VLAN

Explanation

A routed port is configured with an IP address and behaves like a router interface, with no Layer 2 VLAN association. An SVI is a virtual interface that provides Layer 3 processing for a VLAN.

Question 35Wired and wireless network fundamentals (routing/switching)

Two switches are connected with a single link, and each has a management IP in the same subnet. Which protocol allows the switches to discover each other's identity and capabilities on that link?

  1. NTP
  2. SNMP
  3. RADIUS
  4. LLDP Correct answer.

Explanation

LLDP is a neighbor discovery protocol that advertises device identity, port, and capability information to directly connected peers. It operates at Layer 2 and does not require IP reachability.

Question 36Wired and wireless network fundamentals (routing/switching)

A host is configured with mask 255.255.255.192. How many usable host addresses does its subnet provide?

  1. 64
  2. 126
  3. 62 Correct answer.
  4. 30

Explanation

A /26 mask leaves 6 host bits, giving 64 total addresses, of which 2 are reserved for the network and broadcast addresses. That leaves 62 usable host addresses.

Question 37Wired and wireless network fundamentals (routing/switching)

A router running OSPF has an interface with a cost of 10 and another with a cost of 20 toward the same destination network. How does OSPF select the path?

  1. It selects both paths and load balances regardless of cost
  2. It selects the path with the lowest total cost to the destination Correct answer.
  3. It selects the path with the lowest administrative distance
  4. It selects the path with the highest cost to avoid congestion

Explanation

OSPF is a link-state protocol that computes shortest paths using cumulative interface cost, and the lowest total cost wins. Equal-cost paths can be load balanced, but unequal costs are not.

Question 38Wired and wireless network fundamentals (routing/switching)

A switch port configured for 802.1X authentication receives traffic from a device before authentication completes. In a typical port-based deployment, what happens to that traffic?

  1. It is redirected to the RADIUS server for inspection
  2. It is tagged with a quarantine VLAN automatically by the supplicant
  3. It is forwarded normally because 802.1X only logs authentication events
  4. It is blocked except for EAP over LAN traffic needed to complete authentication Correct answer.

Explanation

Before authentication succeeds, the port is in an unauthorized state that permits only EAPoL frames used for the authentication exchange. Other traffic is held until the supplicant authenticates and the port becomes authorized.

Question 39Wired and wireless network fundamentals (routing/switching)

A network engineer must connect two switches with a link that carries several VLANs and also must ensure that untagged frames are placed in a specific VLAN. Which configuration accomplishes this?

  1. Configure the link as a trunk and disable tagging on all VLANs
  2. Configure the link as a trunk and set the native VLAN to the desired VLAN Correct answer.
  3. Configure the link as an access port in the desired VLAN
  4. Configure the link as a routed port with subinterfaces

Explanation

A trunk carries multiple VLANs with tags, and the native VLAN handles untagged frames on that trunk. Setting the native VLAN to the desired VLAN places untagged traffic there.

Question 40Wired and wireless network fundamentals (routing/switching)

A routing table contains a default route, a /24 route, and a /16 route that all match a packet's destination. Which route does the router use?

  1. The route with the lowest metric regardless of prefix length
  2. The /24 route, because it has the longest matching prefix Correct answer.
  3. The default route, because it is evaluated first
  4. The /16 route, because it covers a larger address space

Explanation

Routers use longest-prefix match, so among all matching routes the one with the most specific prefix is chosen. Only routes with the same prefix length are compared by metric or administrative distance.

Question 41Basic RF concepts

Which unit is used to express the power of a radio transmitter relative to 1 milliwatt?

  1. dBm Correct answer.
  2. dBi
  3. dB
  4. mW

Explanation

dBm is a logarithmic power unit referenced to 1 milliwatt, so 0 dBm equals 1 mW. It is the standard way to state absolute RF transmit power and received signal level.

Question 42Basic RF concepts

A signal level increases from 10 mW to 100 mW. What is the change in dB?

  1. 1 dB
  2. 20 dB
  3. 10 dB Correct answer.
  4. 90 dB

Explanation

A tenfold increase in power corresponds to 10 dB, because dB = 10 × log10(P2/P1) and log10(10) = 1. Multiplying power by 10 always adds 10 dB.

Question 43Basic RF concepts

Which term describes an antenna that radiates equally in all directions in three dimensions?

  1. Isotropic radiator Correct answer.
  2. Patch antenna
  3. Yagi
  4. Dipole

Explanation

An isotropic radiator is a theoretical point source that radiates uniformly in every direction and is used as the reference for dBi gain. Real antennas are directional and always have gain measured relative to it.

Question 44Basic RF concepts

Which frequency band is used by IEEE 802.11b/g/n for WLAN operation?

  1. 2.4 GHz Correct answer.
  2. 5 GHz
  3. 900 MHz
  4. 6 GHz

Explanation

802.11b, 802.11g, and 2.4 GHz 802.11n operate in the 2.4 GHz ISM band. This band offers longer range but fewer non-overlapping channels than higher bands.

Question 45Basic RF concepts

How many non-overlapping 20 MHz channels are available in the 2.4 GHz band in North America?

  1. 1
  2. 3 Correct answer.
  3. 11
  4. 14

Explanation

In North America the 2.4 GHz band supports three non-overlapping 20 MHz channels: 1, 6, and 11. Adjacent channels overlap in spectrum and cause co-channel interference if used together.

Question 46Basic RF concepts

What happens to the free-space path loss when the operating frequency is doubled while distance stays constant?

  1. It increases by 6 dB Correct answer.
  2. It increases by 20 dB
  3. It stays the same
  4. It decreases by 3 dB

Explanation

Free-space path loss scales with the square of frequency, so doubling frequency adds 6 dB of loss. This is why higher bands generally provide shorter range at the same power.

Question 47Basic RF concepts

Which modulation scheme is used by 802.11b at 11 Mbps?

  1. OFDM
  2. 64-QAM
  3. DSSS with Barker code
  4. CCK Correct answer.

Explanation

802.11b uses Complementary Code Keying to reach 5.5 and 11 Mbps data rates. Lower 1 and 2 Mbps rates use DSSS with a Barker spreading code.

Question 48Basic RF concepts

An antenna has 6 dBi of gain and is fed with 100 mW. What is the effective isotropic radiated power?

  1. 200 mW
  2. 600 mW
  3. 106 mW
  4. 400 mW Correct answer.

Explanation

EIRP equals transmit power plus antenna gain in dB. 100 mW is 20 dBm, and adding 6 dBi gives 26 dBm, which is about 400 mW.

Question 49Basic RF concepts

What is the primary cause of multipath fading in an indoor WLAN environment?

  1. The use of OFDM subcarriers
  2. Thermal noise in the receiver
  3. Co-channel interference from other APs
  4. Reflections of the signal arriving at different times Correct answer.

Explanation

Multipath occurs when copies of a transmitted signal reflect off walls, floors, and objects and arrive at the receiver with different delays and phases. These copies can add constructively or destructively, causing fading.

Question 50Basic RF concepts

Which phenomenon allows a signal to travel beyond the direct line of sight by bending around obstacles?

  1. Scattering
  2. Absorption
  3. Diffraction Correct answer.
  4. Reflection

Explanation

Diffraction occurs when radio waves encounter an edge or obstruction and bend around it, allowing coverage in shadowed areas. It is most pronounced when the obstacle is comparable in size to the wavelength.