Microsoft Windows XP Unleashed

Preferred DNS Server text box. Also, type the address of

a secondary DNS server in dotted-decimal notation in

the Alternate DNS Server text box.

Figure 17.4 shows the TCP/IP property sheet with assigned IP and DNS server addresses.

CHAPTER 17 Implementing TCP/IP for Internet Connections448

FIGURE 17.4 The General tab with an IP address and a subnet mask filled in.

Wielding the TCP/IP Utilities

Windows XP TCP/IP comes with a few command-line utilities that you can use to review

your TCP/IP settings and troubleshoot problems. Here’s a list of the available utilities:

ARP This utility displays (or modifies) the IP-to-Ethernet or IP-to-Token Ring

address translation tables used by the Address Resolution Protocol (ARP) in

TCP/IP. Enter the command arp -? for the syntax.

NBTSTAT This utility displays the protocol statistics and the current TCP/IP connec-

tions using NBT (NetBIOS over TCP/IP). Enter nbtstat -? for the syntax.

NETSTAT This utility displays the protocol statistics and current TCP/IP connections.

The command netstat -? displays the syntax.

PING This utility can check a network connection to a remote computer. This is

one of the most commonly used TCP/IP diagnostic tools, so I describe it

more detail in the next section.

ROUTE This utility can be used to manipulate a network routing table (LMHOSTS).

Enter route -? for the syntax.

TRACERT This utility can check the route taken to a remote host. I explain this valu-

able diagnostic command in more detail later.

IPCONFIG This utility displays the current TCP/IP network configuration. If you run the

command ipconfig without any switches, the utility returns your system’s

current IP address, subnet mask, and default gateway. If you run the

command ipconfig /all, the utility returns more detailed information, as

shown in Figure 17.5.

Wielding the TCP/IP Utilities 449

17

FIGURE 17.5 The IPCONFIG utility displays information about the TCP/IP configuration.

The PING Command

As you might know, a submarine can detect a nearby object by using sonar to send out a

sound wave and then seeing whether the wave is reflected. This is called pinging an

object.

TCP/IP has a

PING command that performs a similar function. PING sends out a special

type of IP packet—called an Internet Control Message Protocol (ICMP) echo packet—to a

remote location. This packet requests that the remote location send back a response

packet.

PING then tells you whether the response was received. In this way, you can check

your TCP/IP configuration to see whether your host can connect with a remote host.

Here’s the

PING syntax:

ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS] [-r count]

➥[-s count] [[-j host-list] | [-k host-list]] [-w timeout] target_name

-t Pings the specified target_name until you interrupt the command.

-a Specifies not to resolve IP addresses to hostnames.

-n count Sends the number of echo packets specified by count. The default is 4.

-l size Sends echo packets containing the amount of data specified by size. The

default is 32 bytes; the maximum is 8192.

-f Sends a Do Not Fragment flag in the packet’s header. The flag ensures that

the packet won’t be fragmented by gateways along the route.