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.

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