Hi there.

So I write about basic network troubleshooting using windows command line.

Here is my virtual lab network topology.

A: Client network adapter disabled

1: Login client PC

This client gets IP address 10.0.0.200 from DHCP server.

2: Right-click on the Network icon in the notification area, and click Open Network and Internet settings from the context menu.

3:Click Network and Sharing Center from Advanced Network Settings. Change adapter settings link in the left hand-side of the window to view the installed network adapter in the machine.

4:Network Connections window appears, select and right-click the Ethernet adapter, and click Disable from the context menu.

You can see the Ethernet Adapter is disabled as shown in the screenshot.

B: Domain Controller

1:login Domain Controller

2: Open command prompt in Admin mode by right-clicking on Start icon and Command Prompt (Admin) from the context menu.

3:The command prompt appears on the screen. Type “ipconfig” in the command prompt and press Enter to verify IP configuration settings of the machine.

The IP Configuration details of the system will be displayed. As a network admin, you should know the IP configuration details of all the system in the network.

There are different “ipconfig” parameters to perform various network troubleshooting activites.

A: ipconfig/all

Display the full TCP/IP configuration for all adapters.This command lists out complete System’s IP configuration, host name, Ethernet Adapter installed and its MAC Address and so on.

B:ipconfig/renew

Renews DHCP configuration for all adapters

C:ipconfig/release

Sends a DHCPRELEASE message to the DHCP server to release the current DHCP configuration and discard the IP address configuration for either all adapters (if an adapter is not specified) or for a specific adapter.

Once you release, it releases ip address from DHCP. So 169.254…. address shows up.

D:ipconfig/flushdns

Flushes and resets the contents of the DNS client resolver cache.

E:ipconfig/displaydns

Displays the contents of the DNS client resolver cache, Which includes both entries preloaded from the local Hosts file and any recently obtained resource records for name queries resolved by the computer.

F:ipconfig/registerdns

Initiates manual dynamic registration for the DNS names and IP address that are configured at a computer.

4: We explore the usage of Ping command. Network admin always encounter IP level Connectivity errors in the network such as

Request timed out, Destination host unreachable

With the help of Ping command, they can ensure the reachability of host to other hosts connected in the network.

Type ping followed by the IP address of client (it is 10.0.0.200 in this lab) from Domain Controller.

You can see that “Destination host unreachable” error. It means that the target system did not reply within the stipulated time frame. It implies that the target device is out of reach. This caused either due to target machine is turned off or Network adapter is disabled on the target machine.

C: Client Network Adapter enabled

Now switch back to Client

Right-click on disabled network adapter and click Enable.

D: Ping from Domain Controller again

Switch back to Domain Controller machine and ping the target machine (client 10.0.0.200) again

This time, you will be able to ping client successfully.

E:Tracert

Now, we see the usage of “tracert” command to know the number of hops between a source and a destination node in a network. “tracert” is useful for troubleshooting large networks where several paths can lead to the same point or where many intermediate components (routers and bridges) are involved.

Type “tracert” followed by the target system IP address the command prompt and press Enter.

F:Netstat

We see the usage of “netstat” command. Netstat stands for Network statistics. Displays active TCP connections, ports on which the computer is listening, Ethernet statistics, IP routing table, IPv4 statistics (for the IP, ICMP, TCP, and UDP protocols), and IPv6 statistics (for the IPv6, ICMPv6, TCP over IPv6, and UDP over IPv6 protocols). used without parameters, netstat displays actice TCP connections.

These are different netstat parameters to get important connection information.

G:ARP

arp -a command displays ARP cache. The cache has a mapping of IP addresses with their respective MAC addresses. It has many options and if you use APR without any option, it displays the available options.

These are the ARP cache entries

There are different useful commands for network admin and troubleshooting.

Conclusion

We have learned use of basic Windows command line utilities to perform basic troubleshooting in the network.

Hope you enjoyed and learned something.

If you have any comment, just let me know from contact page.

Taka