Legacy Haven University

Windows will not tell you why a user cannot reach a share or why a name will not resolve until you inspect the stack yourself. You open an elevated Command Prompt, you run ipconfig /all, you read the DHCP lease and the DNS servers, and you map the share with net use. Those three actions sit at the center of CompTIA A+ Core 2 objective 1.7 and the command-line list in 1.4.

How the Client Builds Its Address

A Windows NIC starts with no usable IPv4 address. The DHCP client broadcasts a DHCPDISCOVER. The first DHCP server that answers offers an address, a subnet mask, a default gateway, and one or more DNS servers. The client accepts the offer, the lease timer starts, and the stack writes the values into the adapter.

You see the result with a single command:

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ipconfig

The output lists IPv4 address, subnet mask, and default gateway for every adapter. Add the /all switch and the same command also prints the MAC address, DHCP server, lease obtained/expires times, DNS servers, and whether Autoconfiguration is enabled.

When Autoconfiguration is Yes and the address sits in 169.254.0.0/16, DHCP failed. Windows assigned an APIPA address so the machine can still talk to other APIPA hosts on the same L2 segment. That address never reaches the internet. The exam expects you to recognize 169.254 immediately and then run ipconfig /release followed by ipconfig /renew to force a new DHCP conversation.

Static configuration skips DHCP. You type the four values yourself: address, mask, gateway, DNS. Use static only when the device must keep the same address (printer, file server, or a lab box that other machines reference by IP). Everywhere else, leave DHCP on.

DNS Resolution on the Client

DNS turns fileserver.corp.local into an IP address. The Windows resolver first checks its local cache, then the hosts file, then the DNS servers listed in ipconfig /all. You empty the cache with ipconfig /flushdns. You watch the query itself with nslookup fileserver.corp.local.

In a workgroup the DNS servers usually belong to the ISP or to a public resolver. In a domain the first DNS server must be a domain controller. Active Directory publishes SRV records under _ldap._tcp.dc._msdcs.domain. If the client points at 8.8.8.8 instead of the DC, the join fails with “An Active Directory domain controller could not be contacted.” That single misconfiguration is the most common domain-join ticket you will see.

Register the client’s own A record after a name or address change with ipconfig /registerdns. The command forces the DHCP client to renew and then writes the current IP into DNS.

Workgroup Versus Domain and How Shares Travel

A workgroup is a peer list. Each computer keeps its own user accounts. A domain is a single account database on a domain controller. Once the PC joins the domain, a user logs on once and the ticket grants access to every share the administrator published.

Shares travel over SMB. The path uses UNC syntax:

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\\FILES01\Finance

A trailing dollar sign hides the share from Network browse lists (\\FILES01\Finance$). Administrative shares (C$, ADMIN$) already exist; you do not create them.

Map the UNC path to a drive letter so users never type the path again:

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net use S: \\FILES01\Finance /persistent:yes

/persistent:yes writes the mapping into the user’s profile so it returns after reboot. net use without arguments lists every current mapping. net use S: /delete removes one.

Share permissions and NTFS permissions both apply. Sitting at the console bypasses share permissions and uses only NTFS. That is why a folder “works for me but not over the network.”

Network Location Profiles Control Discovery

Windows labels every network Public, Private, or Domain. Public turns off network discovery and file sharing; use it on coffee-shop Wi-Fi. Private turns both on; use it on a trusted home or office LAN. Domain is set automatically when Group Policy applies. Change the profile in Settings → Network & Internet → the adapter → Properties, or with PowerShell Set-NetConnectionProfile.

The same profile also drives Windows Defender Firewall. An inbound file-share rule that is scoped to Private will not fire on a Public network. That is the intended behavior, not a bug.

Quick Diagnostic Sequence the Exam Expects

1. ipconfig /all — confirm address, mask, gateway, DNS, DHCP vs APIPA.
2. ping the gateway, then an external IP, then a name.
3. nslookup the same name.
4. ipconfig /flushdns if the cache is stale.
5. net use to confirm or rebuild the mapped drive.

Run those five commands in order and you isolate most “no internet” and “cannot see the share” tickets before you open the GUI.

Students who treat these commands as muscle memory rather than trivia pass the performance-based questions and the real help-desk queue. For a structured study path that lines every 220-1202 objective with labs, see https://legacyhaven.university/how-to-pass-comptia-a-core-2-220-1202/.