2.6 - Networking devices: routers, DHCP and VLANs
CompTIA A+ Core 1 objective 2.6 covers core network devices and services. A router operates at Layer 3 of the OSI model and forwards traffic between different IP networks. A DHCP server automatically assigns IP addresses, subnet masks and other settings to clients, saving manual configuration. A VLAN segments one physical switch into separate broadcast domains, so groups of ports behave like separate networks for security and traffic control. Recognising which device or feature does the job is the goal. Expect scenario questions that describe routing between networks, handing out addresses automatically, or logically separating traffic on one switch, and ask which device or technology - router, DHCP or VLAN - is correct. Anchor each to its one job: route between networks, assign addresses, or segment a switch.
Route between IP networks (Layer 3) = router. Auto-assign IP addresses = DHCP. Split one switch into separate broadcast domains = VLAN.
Practice questions
1. Which technology segments one physical switch into separate broadcast domains?
- NAT
- VLAN (correct answer)
- DHCP
- PoE
VLANs logically separate ports into different broadcast domains for segmentation and security.
2. Which DNS record maps a hostname to an IPv4 address?
- MX
- A (correct answer)
- CNAME
- TXT
An A record maps a name to an IPv4 address. AAAA=IPv6, MX=mail server, CNAME=alias, TXT=text (SPF/verification).
3. Which device operates at Layer 3 of the OSI model and routes traffic between different networks?
- Unmanaged switch
- Router (correct answer)
- Repeater
- Hub
A router works at Layer 3 (Network) using IP addresses to forward packets between networks. Switches/hubs are Layer 2/1.
4. Which server automatically assigns IP addresses to clients?
- DNS
- DHCP (correct answer)
- NTP
- SMTP
DHCP leases IP addresses, subnet mask, gateway and DNS to clients automatically (ports 67/68).
5. Which device forwards traffic between different IP networks?
- Unmanaged switch
- Hub
- Router (correct answer)
- Access point
A router operates at Layer 3 and forwards packets between networks using IP addresses.
6. Which describes a WAN?
- A network within a single room
- Two nearby PCs paired over Bluetooth
- A network spanning large distances (correct answer)
- A single locally hosted virtual machine
A WAN connects networks across large distances (e.g., the internet, multi-site links). A LAN is local.