CSLB General Building (B) — All Questions
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An administrator is terminating a straight-through Ethernet cable using the T568B standard on both ends. Which pin arrangement starts the sequence?
- a.White-green, green, white-orange, blue
- b.White-orange, orange, white-green, blue✓
- c.White-brown, brown, white-blue, green
- d.Orange, white-orange, green, white-green
The T568B wiring order begins with white-orange, orange, white-green, blue on pins one through four. Using the same standard on both ends creates a straight-through cable. Mixing T568A and T568B on opposite ends creates a crossover.
Which technology allows a switch to supply electrical power to devices such as IP phones and access points over the data cable?
- a.QoS
- b.STP
- c.PoE✓
- d.NAT
Power over Ethernet (PoE) delivers electrical power and data over the same twisted-pair cable, powering devices like IP phones, cameras, and access points. This removes the need for separate power adapters. Standards include 802.3af, 802.3at, and 802.3bt.
When implementing inter-VLAN routing on a single router interface, what configuration is required?
- a.Router-on-a-stick using subinterfaces with 802.1Q tagging✓
- b.A separate physical router for each VLAN
- c.Disabling all trunk links to the switch
- d.Assigning every VLAN the same subnet
Router-on-a-stick uses a single physical interface divided into subinterfaces, each tagged for a VLAN with 802.1Q, to route between VLANs. This avoids needing one physical interface per VLAN. A Layer 3 switch is an alternative that uses SVIs.
A wireless network must support the highest client density in a crowded office. Which deployment choice best reduces co-channel interference on 2.4 GHz?
- a.Set every access point to channel 6
- b.Use overlapping channels 1, 2, and 3
- c.Increase transmit power to maximum on all APs
- d.Use non-overlapping channels 1, 6, and 11✓
In the 2.4 GHz band, channels 1, 6, and 11 are the only non-overlapping options, so alternating them between adjacent APs minimizes co-channel and adjacent-channel interference. Maxing transmit power actually worsens interference. Proper channel planning is key to dense deployments.
Which routing protocol is a link-state interior gateway protocol that uses cost based on bandwidth as its metric?
- a.RIP
- b.OSPF✓
- c.BGP
- d.EIGRP
OSPF is a link-state interior gateway protocol that calculates the shortest path using a cost metric derived from link bandwidth. RIP uses hop count and BGP is a path-vector exterior protocol. OSPF converges faster than distance-vector protocols in large networks.
An engineer configures a static route of last resort. Which destination and mask represent the default route?
- a.255.255.255.255/32
- b.127.0.0.0/8
- c.0.0.0.0/0✓
- d.169.254.0.0/16
The default route is written as 0.0.0.0/0, matching any destination not covered by a more specific route. It directs otherwise-unmatched traffic to a next hop, often the internet gateway. This is commonly called the gateway of last resort.
Which protocol prevents Layer 2 switching loops by placing redundant links into a blocking state?
- a.Spanning Tree Protocol✓
- b.Border Gateway Protocol
- c.Hot Standby Router Protocol
- d.Network Time Protocol
Spanning Tree Protocol (STP) detects redundant Layer 2 paths and blocks them to prevent broadcast storms and switching loops. If an active link fails, a blocked link can transition to forwarding. STP is essential in networks with redundant switch links.
A technician needs to connect two buildings 800 meters apart with high bandwidth and immunity to electromagnetic interference. Which medium is best?
- a.Cat 6 UTP
- b.Coaxial cable
- c.Cat 5e UTP
- d.Single-mode fiber✓
Single-mode fiber supports long distances well beyond copper's 100-meter limit and is immune to electromagnetic interference. Twisted-pair copper cannot reach 800 meters. Fiber is the standard choice for building-to-building backbone links.
Which addressing technique allows many internal private hosts to share a single public IP address for internet access?
- a.DHCP
- b.PAT✓
- c.VLSM
- d.ARP
Port Address Translation (PAT), a form of NAT overload, lets multiple private hosts share one public IP by tracking unique source port numbers. This conserves scarce public IPv4 addresses. Each session is distinguished by its translated port.
When configuring a trunk between two switches, which VLAN carries untagged traffic by default?
- a.The management VLAN only
- b.VLAN 4094
- c.The native VLAN✓
- d.The voice VLAN
The native VLAN carries untagged traffic across an 802.1Q trunk. By default it is VLAN 1, but it should be changed and matched on both ends for security. Mismatched native VLANs can cause connectivity and security problems.
Which wireless security standard introduces Simultaneous Authentication of Equals (SAE) to replace the pre-shared key handshake?
- a.WPA3✓
- b.WPA2
- c.WEP
- d.WPA
WPA3 replaces the WPA2 four-way handshake with SAE, providing stronger protection against offline dictionary attacks. WEP and the original WPA are outdated and insecure. WPA3 is the current recommended standard for wireless security.
A network requires automatic failover of the default gateway between two routers. Which category of protocol provides this?
- a.Link aggregation protocol
- b.Spanning tree protocol
- c.Address resolution protocol
- d.First hop redundancy protocol✓
First hop redundancy protocols such as HSRP, VRRP, and GLBP provide a virtual gateway IP shared by multiple routers for automatic failover. If the active router fails, a standby takes over transparently to hosts. This eliminates the gateway as a single point of failure.
Which technology bundles multiple physical links into one logical link to increase bandwidth and provide redundancy between switches?
- a.VLAN trunking
- b.Link aggregation (LACP)✓
- c.Port mirroring
- d.Spanning tree
Link aggregation, often using LACP (802.3ad), combines several physical ports into a single logical link for greater bandwidth and redundancy. If one member link fails, traffic continues over the others. It is commonly used on switch uplinks and server connections.
An administrator assigns 192.168.1.0/24 but needs subnets of varying host sizes. Which technique allows different subnet mask lengths within the same address block?
- a.CIDR summarization
- b.Classful addressing
- c.VLSM✓
- d.APIPA
Variable Length Subnet Masking (VLSM) lets an administrator apply different mask lengths to subnets within the same network, matching each subnet's host requirement. This conserves address space compared with fixed-size subnets. VLSM requires classless routing protocols.
Which DHCP component defines the range of IP addresses a server can lease to clients?
- a.Scope✓
- b.Reservation
- c.Exclusion
- d.Relay
A DHCP scope defines the pool of addresses available for lease on a given subnet. Reservations assign fixed addresses to specific MACs, and exclusions remove addresses from the pool. Relays forward DHCP requests across subnets.
A technician must extend a wired network into an area where running new cable is impractical. Which device bridges two network segments over the existing electrical wiring?
- a.A media converter
- b.A powerline (Ethernet-over-power) adapter✓
- c.A KVM switch
- d.A loopback plug
Powerline adapters, also called Ethernet-over-power, transmit network data over a building's existing electrical wiring to bridge segments. This avoids running new Ethernet cable. Performance varies with wiring quality and distance.
Which SDN plane is responsible for making forwarding decisions and building the network's logical topology?
- a.Data plane
- b.Management plane
- c.Physical plane
- d.Control plane✓
In software-defined networking, the control plane makes forwarding decisions and maintains the logical topology, then programs the data plane. Separating these planes centralizes intelligence in an SDN controller. The data plane simply forwards packets based on control-plane instructions.
An engineer configures a switch port that should immediately transition to forwarding for a single end host. Which STP feature is appropriate?
- a.Root guard
- b.BPDU flooding
- c.PortFast✓
- d.Trunk negotiation
PortFast lets an access port skip the listening and learning states and move directly to forwarding, which is safe for ports connected to a single end device. It should not be enabled on ports connected to other switches. BPDU guard is often paired with it for protection.
Which type of NAT maps one private IP address to one dedicated public IP address permanently?
- a.Static NAT✓
- b.Dynamic NAT
- c.Port Address Translation
- d.Overloaded NAT
Static NAT creates a permanent one-to-one mapping between a private and a public address, often used to expose an internal server. Dynamic NAT pulls from a pool, and PAT overloads a single public IP. Static NAT provides consistent inbound reachability.
Which Layer 3 switch feature provides a virtual interface used to route traffic for a VLAN without a separate router?
- a.A trunk port
- b.A native VLAN
- c.A loopback plug
- d.A switched virtual interface (SVI)✓
A switched virtual interface (SVI) is a virtual Layer 3 interface on a multilayer switch that routes traffic for an associated VLAN. This enables inter-VLAN routing entirely within the switch, avoiding router-on-a-stick. Each routed VLAN typically has its own SVI acting as the default gateway.