Diagnosing IP Address Problems

On most networks, IP addresses are assigned automatically by Dynamic Host Configuration Protocol (DHCP) servers; in some cases, you need to use static IP addresses, which are fixed numeric addresses Problems with DHCP servers or clients can cause network connections to stop working, as can incorrectly assigned static IP addresses

To see details of your current IP configuration, follow these steps:

1. In Network And Sharing Center, click Change Adapter Settings .

2. Double-click the icon for the connection about which you want more information . (Alternatively, you can select the icon and click View Status Of This Connection on the toolbar )

- Local Area Connection Status iü

General

Connection -

IPv4 Connectivity: IPv6 Connectivity: Media State: Duration:

No Internet access Enabled

11:57:24 l.OGbps

Internet

Activity

Received

Bytes:

228,374,782

1,685,794,888

Close

3. Click Details to see the currently assigned IP address, subnet mask, and default gateway for that connection . (If you have IPv4 and IPv6 connectivity, the Network Connection Details dialog box shows information for both .) In the following example, you can tell that the IP address was automatically assigned by the DHCP server in a router; details indicate that DHCP is enabled and the DHCP server address matches that of the router.

Network Connection Details

Network Connection Details:

Network Connection Details

Network Connection Details:

Property

Value

Connection-specific DN...

charter.com

Description

Intel(R) 82566DC Gigabit Network Conne

Physical Address

00-19-D1-E3-CE-FC

DHCP Enabled

Yes

IPv4 Address

192.168.0.107

IPv4 Subnet Mask

255.255.255.0

Lease Obtained

Thursday, July 30, 2009 7:20:46 AM

Lease Expires

Friday, July 31, 2009 6:34:04 PM

IPv4 Default Gateway

192.168.0.1

IPv4 DHCP Server

192.168.0.1

IPv4 DNS Server

192.168.0.1

IPv4 WINS Server

NetBIOS over Tcpip En...

Yes

Link-local IPv6 Address

fe80::6923:87c9:a09d:8a83OT

IPv6 Default Gateway

IPv6 DNS Server

< E

Close

You can also get details of your IP configuration by using the IP Configuration utility, Ipcon-fig. exe, in a Command Prompt window. Used without any parameters, typing ipconfig at a command prompt displays the DNS suffix, IPv6 and/or IPv4 address, subnet mask, and default gateway for each network connection . To see exhaustive details about every available network connection, type ipconfig /all.

The actual IP address you see might help you solve connection problems:

• If the address is in the format 169.254xy, your computer is using Automatic Private IP Addressing (APIPA). This means your computer's DHCP client was unable to reach a DHCP server to be assigned an IP address . Check the connection to your network.

• If the address is in one of the blocks of IP addresses reserved for use on private networks (for details, see "Setting IP Addresses" on page 694), make sure that a router or residential gateway is routing your internet requests to a properly configured public IP address

• If the address of your computer appears as 0. 0. 0 . 0, the network is either disconnected or the static IP address for the connection duplicates an address that already exists on the network.

• Make sure you're using the correct subnet mask for computers on your local network. Compare IP settings on the machine that's having problems with those on other computers on the network . The default gateway and subnet mask should be identical for all network computers . The first one, two, or three sets of numbers in the IP address for each machine should also be identical, depending on the subnet mask. A subnet mask of 255.255.255.0 means the first three IP address numbers of computers on your network must be identical—192.168.0.83 and 192.168.0.223, for instance, can communicate on a network using this subnet mask, but 192.168.1.101 will not be recognized as belonging to the network. Likewise, with a subnet mask of 255.255. 0.0, the first two numbers in each address must match—172. 16.2.34, 172.16.4.56, and 172.16.83.201 are all valid addresses on a subnet with this mask. In every case, the gateway machine must also be a member of the same subnet. (If you use a router, switch, or residential gateway for internet access, the local address on that device must be part of the same subnet as the machines on your network.)

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