**FIGURE 17-11 Determining the MAC address of the interface.**
**FIGURE 17-12 Determine the subnet for the interface.**
Let's start by determining the IP address of the interface. Use the `ipconfig /all` command to check the IP addresses of all adapters. Figure 17-11 shows the output for my computer. The adapter's MAC address is shown in the _adapter_ column. The Ethernet ( _e_ ) column shows the physical address of the Ethernet adapter, and the _IP Address_ column shows the IP address of that adapter. Next, you need to determine the subnet mask of the interface. You can do this by looking in the _subnet_ column for a network number, such as 10. Then use the mask to calculate the starting address for the subnet. You can then continue to the subnet assignment in Step 5.
**FIGURE 17-13 Getting the Mac address for the adapter.**
Now use the `arp -a` command to show the MAC address associated with the Ethernet adapter. The `arp -a` command has a flag that tells you how to interpret the returned information. On my computer, the output is shown in Figure 17-13. The _interface name_ column shows the Ethernet interface. The _IP Address_ column shows the interface's IP address. The _Hardware Address_ column shows the adapter's MAC address, which is the same as the interface's MAC address.
If you want to assign a subnet to an interface, perform the following steps:
**1.** Use the `ip address add subnet_mask subnet_start_address` command. (There's no need to include a subnet mask, because this is the default.)
**2.** The `ip address add` command adds an IP address to an interface. The `subnet_mask` command accepts the starting IP address, subnet mask, and network mask. The `subnet_start_address` adds the starting IP address to the interface.
**3.** The `interface ip address add` command works like the previous one but only adds the IP address to the specified interface.
**4.** The `ip address add` command uses the default subnet mask.
Now that you have the IP address, MAC address, and subnet mask for the interface, you need to register the product.
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