IP address conflict help and setting up security code for access

Question

Hi folks, I am about as non-technical as one can get. So I apologize in advance and thank you guys for your patience as everything you tell me will have to be spelled out for me.
Ques 1:  I have one desk top computer with internet access through my cable TV provider. On it I have the Linksys WRT54G wireless router.  We use two laptops.
Lately I've been getting an error message on my desktop saying there is an IP Address that is in conflict. My son often gets booted off line (on laptop) and so I'm guessing maybe it is his laptop that is in conflict. Please help me resolve this issue.
Quest 2:  I would like to set up a security code for our wireless access so that other people will not be able to intrude upon our signal. Can someone walk me through this as well?
Thank you so much!
-Jen in NJ

Answer 1

The most common reason to get two identical IP addresses, is if you are using fixed LAN IP addresses incorrectly on your system.
Do you already use any fixed LAN IP addresses? If so, please state what fixed LAN IP addresses you are using, and also state your DHCP server range.
Rules for using fixed LAN IP addresses on Linksys routers:
With Linksys routers, a fixed (static) LAN IP addresses must be assigned in the device that is using the address. So you need to enter the fixed address in the computer or printer, not in the router.
When using a Linksys router, any fixed LAN IP address must be outside the DHCP server range (typically 192.168.1.100 thru 192.168.1.149), and it cannot end in 0, 1, or 255.
Therefore any fixed LAN IP address would normally need to be in the range of
192.168.1.2 thru 192.168.1.99 or
192.168.1.150 thru 192.168.1.254
assuming you are still using the default DHCP server range.
Also, in the computer, when you set up a static LAN IP address, you would need to set the "Subnet mask" to 255.255.255.0 and the "Default Gateway" to 192.168.1.1 and "DNS server" to 192.168.1.1
It is also important that no two devices on your network be set to the same static LAN IP address.
Check all of your static LAN IP addresses. If you have violated any of the above rules for static LAN IP addresses, it could be the cause for your problem, and you should fix it before attempting any other router repairs or changes.
*********  Wireless Security  **********
Brfore proceeding with wireless security, you must get your IP address conflict problem solved.  Please do the above first.
To set up wireless security, you must use a computer that is wired to the router.
Where to find the router settings: The router's login password is usually on one of the "Administration" pages. The other settings are all found in the "Wireless" or the "Security" section of the router's setup pages, located at 192.168.1.1
First, give your router a unique SSID. Don't use "linksys".
Make sure "SSID Broadcast" is set to "enabled".
Next, leave the router at its default wireless settings (except for the unique SSID), and then use your pc to connect wirelessly to the router. Test your wireless Internet connection and make sure it is working correctly. You must have a properly working wireless connection before setting up wireless security.
To implement wireless security, you need to do one step at a time, then verify that you can still connect your wireless computer to the router.
Next, encrypt your wireless system using the highest level of encryption that all of your wireless devices will support. Common encryption methods are:
WEP - poor (see note below)
WPA (sometimes called PSK, or WPA with TKIP) - good
WPA2 (sometimes called PSK2, or WPA with AES) - best
WPA and WPA2 sometimes come in versions of "personal" and "enterprise". Most home users should use "personal". Also, if you have a choice between AES and TKIP, and your wireless equipment is capable of both, choose AES. With any encryption method, you will need to supply a key (sometimes called a "password" ).
The wireless devices (computers, printers, etc.) that you have will need to be set up with the SSID, encryption method, and key that matches what you entered in the router.
Retest your system and verify that your wireless Internet connection is still working correctly.
And don't forget to give your router a new login password.
Picking Passwords (keys): You should never use a dictionary word as a password. If you use a dictionary word as a password, even WPA2 can be cracked in a few minutes. When you pick your login password and encryption key (or password or passphrase) you should use a random combination of capital letters, small letters, and numbers, but no spaces. A login password, should be 12 characters or more. WPA and WPA2 passwords should be at least 24 characters. Note: Your key, password, or passphrase must not have any spaces in it.
Most home users should have their routers set so that "remote management" of the router is disabled. If you must have this option enabled, then your login password must be increased to a minumum of 24 random characters.
One additional issue is that Windows XP requires a patch to run WPA2. The patch is located in SP3, so you will need SP3 to run WPA2 in Win XP. Vista already supports WPA2.
Note:
WEP is no longer recommended. The FBI has demonstrated that WEP can be cracked in just a few minutes using software tools that are readily available over the Internet. Even a long random character password will not protect you with WEP. You should be using WPA or preferably WPA2 encryption.