Most Small Office/Home Office (SOHO) equipment uses the Dynamic Host Control Protocol (DHCP) for use with Internet connections. DHCP makes configuration of most network hardware automatic: no need to look up or memorize Internet Protocol (IP) address rules, for example.
DHCP address assignments, however, are only temporary. Usually when an address expires, DHCP gets a new one automatically. If this process fails, however, a device won't be able to connect to the Internet due to a stale address.
A stale address can be resolved by power cycling the equipment. Nine times out of ten, this fixes the connection. And stale addresses, while rare, do impact all operating systems: Apple® Classic and OSX®, Linux®, or Microsoft Windows®.
Windows users who have upgraded to Service Pack 2 (SP2) may also experience the "dueling firewall" problem: this happens when SP2 is installed on a system already running McAfee® or Norton® firewall software. We discuss steps for resolving this problem too.
We obtain fresh DHCP addresses by performing the following steps:
This forces each piece of networking equipment on the LAN to refresh its DHCP client or server: usually modems and routers run DHCP servers and computers run DHCP clients. At power-up, device address ranges are updated. If the Wide Area Network (WAN) address schema changed, which happens about once every six months, DHCP will import the fresh configuration.
Note the power-down sequence is equipment farthest from the WAN first and power-up is the reverse: equipment closest to the WAN first. This sequence is mandatory to prevent data loss: powering off a router, for example, before shutting down attached computers can scramble existing network connections.
Windows XP computers running automatic Windows Update or manual SP2 installations may stop some types of IP connections. This happens when a computer is already running a software firewall and there is a conflict between it and the automatically installed SP2 firewall To repair this problem, turn one firewall off.
Please note: administrative privileges are required to perform this operation. Normally, one should run as an ordinary user. See our article on defensive security for reasons why.
Step 1: Open the Network Connections Folder: Click Start, right click My Network Places, and select Properties. Or click Start, right click Network Connections, and select .
Step 2: Set Tiles View: Select View from the Network Connections folder menu, then choose Tiles if it's not already checked. Most of the time, this is checked by default.
Step 3: Determine if the LAN Connection is Firewalled: Look to see if the word "firewalled" appears after any Internet connection: Dial-Up, Local Area, or Wireless.
Step 4: Turn off the SP2 Firewall: Right click on a network connection and select Properties. In the resulting dialog box, click the Advanced tab, click the Off radio button for the Windows Firewall, and click Apply. Then click OK. Do this for all firewalled connections.
Firewalls protect us from the Internet equivalent of a drive-by shooting: abusers "poke" a computer for ungaurded IP ports and try to exploit them. A firewall simply denies any incoming Internet connection unless it is in response to an already initiated outgoing connection.
This denial can be performed by hardware or software. For one computer on a Cable or DSL modem, software makes sense. But if multiple computers share an Internet connection with a router, chances are the router has a built-in firewall already. So running a software firewall just slows down the computer without providing an additional benefit.
We recommend turning off ALL software firewalls for LANs using a hardware firewall with appropriately patched, up-to-date firmware. If there is a question if this applies to your LAN, please give us a call.
Feel free to call (number below) or send us email if you have questions about this tip.
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+1 214 234 9283 |