Windows Server 2008 Server Core : Working with Scripts - Scripting Networking Solutions with the NetSH Utility

The Network Command Shell (NetSH) utility extends this idea by providing an extensible command processor. You access the functionality that this utility provides by loading a helper Dynamic Link Library (DLL). Each helper DLL places the NetSH utility into a different context. The use of helper DLLs theoretically makes it possible for third-party vendors to add NetSH functionality as part of their network product installation. One of the essential commands to know for NetSH, since it's so flexible, is NetSH Show Helper. This command displays a list of helper DLLs installed on your machine, which may differ from the list shown in Figure 6.2 based on the operating system features you have installed.

Notice the hierarchy of contexts displayed in Figure 1. To access the IP context at the command line, you must type NetSH Interface IP and then the command you wish to use. Likewise, if you want to access the 6To4 context, you must type NetSH Interface IPv6 6To4 at the command line. Typing any context by itself (or followed by a question mark (?) or Help) displays the list of commands for that context.

Figure 1. Obtain a list of helper DLLs for your setup using the NetSH Show Helper command.

Type a command to see the list of subcommands or the instructions for using that command. Type a subcommand to see the instructions for using that subcommand. For example, to discover how to add a new IP address, type NetSH Interface IP Add Address at the command prompt and press Enter. You'll see a help display explaining the command, as shown in Figure 2. Figure 2 shows the Server Core view of the help for this command. If you're familiar with previous versions of Windows, you'll notice that the Server Core help is an improvement.

Figure 2. The multilevel command structure provided by NetSH provides you with help at each step.

The NetSH utility provides access to a broad range of networking functionality using contexts. Each context represents a different functional network area such as configuring the firewall or modifying security. You can interact with NetSH at the command line, in an interactive environment, and using scripts. In this case, a script file is simply a list of commands that you want NetSH to perform. You place these commands in a text file and pass them to NetSH to execute. This utility uses the following syntax:

netsh [-a AliasFile] [-c Context] [-r RemoteMachine]
[-u [DomainName\]UserName] [Command | -f ScriptFile]

The following list describes each of the command line arguments.

-a

AliasFile

Specifies the alias file to use. An alias file contains a set of strings and their associated NetSH equivalents. You can use the alias in place of the corresponding NetSH command. This feature also allows you to map older commands to the appropriate NetSH command.

-c

Context

Defines the context of the command that you want to run. A context refers to a specific helper DLL.

Command

Specifies the NetSH command to execute. The command is helper DLL specific.

-f

ScriptFile

Specifies the name of a file that contains NetSH commands. A script file is simply a text file that contains NetSH commands one after another. You can use the pound (#) symbol followed by text to create script file comments. Use the NetSH Dump command to display a sample script. Because the script is long, you might want to use redirection to send the output to a file .

-r

RemoteMachine

Defines the name or IP address of a remote machine to use to execute NetSH commands. This feature helps you manage remote systems.

-u

[DomainName\]UserName

Specifies the credentials to use to log into a system. Server Core prompts you for a password when logging into another system.

The various helper DLLs provide contexts that you can use to perform specific tasks. You can access some of these contexts directly from the command line using a command. Table 1 describes each of the top-level contexts.

Table 1. Standard NetSH Contexts

Context Name	Windows Version	Description
Bridge	Windows XP and above	Shows configuration information for network adapters that are part of a network bridge. You can also use this context to enable or disable Level 3 compatibility mode.
Diag	Windows XP and above	Performs network diagnostic commands. For example, you can use this context to display network service status information or perform diagnostics similar to the Ping utility . A special NetSH Diag GUI command displays a Web page in the Help and Support Center that provides access to the network diagnostics.
Firewall	Windows XP and above	Provides complete access to the Windows firewall. You can use this context to add and remove configuration information, as well as display the current firewall state.
Interface	Windows 2000 and above	Provides access to the network interfaces installed on your machine, which normally include IP, IPV6 (Windows XP and above), and standard port proxies. You can use this context to configure the TCP/IP protocol including addresses, default gateways, DNS servers, and WINS servers.
RAS	Windows 2000 and above	Provides access to the Remote Access Server (RAS) and all of its configuration information. For example, this context provides access to the Authentication, Authorization, Accounting, and Auditing (AAAA) subcontext where you perform security setups.
Routing	Windows 2000 and above	Helps you configure the routing features of the system using a command line interface, rather than rely on the Routing and Remote Access console. The biggest advantage of the command line interface, in this case, is speed. You can access and manage remote servers over a large network, especially wide area networks (WANs) much faster using NetSH than you can the graphical equivalents. In addition, since these configuration tasks can become quite complex, you gain the advantage of scripting them once, rather than going through every required step each time you perform the task.
WinSock	Windows XP and above	Shows Windows Socket (WinSock) information for the current system. You can also use this context to dump the WinSock configuration script.

The default context is the root context, the NetSH utility itself. You can use specific commands from this context to perform configuration tasks or access other contexts. The following list describes the command line arguments, which differ according to the version of Windows that you use and the networking features you have installed.

add

Adds a configuration entry to the list of entries. When working at the root context, you can add new helper DLLs to the list.

delete

Deletes a configuration entry from the list of entries. When working at the root context, you can remove a helper DLL from the list.

dump

Displays a configuration script. The script is quite long, so you'll want to use redirection to store the script to a file.

exec

Executes the specified script file.

interface

Sets NetSH to use the interface context.

ras

Sets NetSH to use the RAS context.

routing

Sets NetSH to use the routing context.

set

Updates the configuration settings. Most versions of NetSH only allow you to set the machine name when working at the root context.

show

Displays NetSH configuration information. Most versions of NetSH provide commands to display both the list of aliases and the list of helpers installed on the system.

Windows XP and above provide additional functionality to support items such as the firewall. Here are the Windows XP additions.

bridge

Sets NetSH to use the bridge context.

diag

Sets NetSH to use the diag context.

firewall

Sets NetSH to use the firewall context.

winsock

Sets NetSH to use the WinSock context.

Windows 2003 and above supports still more commands. The following list describes the Windows 2003 additions.

cmd

Creates a command window where you can enter NetSH commands manually.

comment

Executes any commands accumulated in offline mode.

flush

Discards the commands accumulated in offline mode.

online

Sets the current mode to online. In online mode, which is the default for all previous versions of NetSH, the utility executes immediately any command you issue. Use the show mode command to display the current mode.

offline

Sets the current mode to offline. In offline mode, which was new for Windows 2003, the utility accumulates any commands you issue and executes them as a batch. Using this second approach on remote servers can greatly enhance performance without any loss of functionality. Use the show mode command to display the current mode.

pushd

Pushes a context onto the NetSH stack. 

popd

Removes a context from the NetSH stack.