Lab 1: Build a Basic Office LAN

Scenario: New Four-Person Office

You are asked to bring up a small office with four desktops, one network printer, one wireless access point, an Ethernet switch, and an Internet router or firewall. An engineer provides the diagram: the router LAN interface is the default gateway at 192.168.50.1/24, the DHCP pool is 192.168.50.100 through 192.168.50.199, the printer will use reserved address 192.168.50.20, and the access point management address will be 192.168.50.30. The switch is unmanaged or preconfigured, so your work is to cable accurately, verify link, and confirm client addressing.

Start with the physical build. Match the diagram to the room labels, patch panel labels, and device ports. Use copper Ethernet patch cables with the correct connectors for the switch, router LAN port, printer, access point, and desktop drops. Check that the switch uplink goes to the router LAN side, not to the router WAN or Internet port. Watch link and activity indicators after each connection. A link light does not prove IP service is correct, but it is an important first checkpoint. If a port stays dark, swap the patch cable, try a known-good switch port, check the wall jack label, and document the result.

Next verify the local addressing plan. A desktop set to DHCP should receive an address in 192.168.50.0/24, a subnet mask of 255.255.255.0, default gateway 192.168.50.1, and DNS servers supplied by the router or upstream service. If the client receives 169.254.x.x, it has not received a usable DHCP lease. If it receives an address from a different subnet, it may be connected to the wrong network, wrong VLAN, wrong SSID, or wrong router. Before changing settings, capture the evidence: current IP address, mask, gateway, DNS server, switch port, wall jack, and device name.

Then test in a practical order. Ping the client's own default gateway first. If that fails, focus on the local path: cable, switch port, router LAN interface, host firewall behavior, or address mismatch. If the gateway responds, ping another local device such as the printer. If local tests pass, test an Internet IP address and then a DNS name. When IP works but names fail, DNS is the likely area to investigate. When names resolve but web pages still fail, filtering, proxy, application, or upstream Internet issues may be involved.

Do not treat the printer and access point as afterthoughts. The printer's reserved address should not overlap with the DHCP pool unless the reservation is handled by the DHCP service. The access point should connect to the intended LAN and should not run a second DHCP server unless the design specifically calls for it. A home-style router accidentally connected behind the office router can create double NAT, duplicate DHCP, or a separate private network that isolates clients.

Close the lab with documentation. Record the installed device model, serial number if required by local practice, switch port, wall jack, IP information, SSID if wireless is enabled, and test results. Escalate if the diagram conflicts with the physical labels, if the router LAN settings do not match the approved addressing plan, if DHCP cannot be verified from the router or server, or if a managed switch needs configuration you are not authorized to perform.

Study Checkpoint

• Topic: Lab 1: Build a Basic Office LAN.
• Verify the official Cisco concept before memorizing a shortcut.
• Practice the technician action: observe, document, test, fix when supported, or escalate.