Cannot see computers on network

May 16, 2007

First thing, turn off the security software temporarily to troubleshoot.

Check to make sure port 135 and 139 are not blocked in any software firewall you may be running, or in the router itself (used for file sharing). The computers should be in the same workgroup (right-click ‘my computer’, click on ‘computer name’ tab).

Try pinging one computer from the other to see if it responds on the network. Open the start menu, click the ‘run’ button, and type ‘cmd’. When the command prompt window opens, type ‘ping XXX.XXX.XXX’, replacing the X’s with the other computer’s IP address (which you can find on the other computer typing ‘ipconfig’.


Routers, Hubs, Switches

December 30, 2006

Router                                                                                                                                                                                                         a computer networking device that forwards data packets across a network toward their destinations, through a process known as routing. Routing occurs at Layer 3 (the network layer i.e. Internet Protocol (IP)) of the OSI seven-layer protocol stack.  (source:

Switch                                                                                                                                                                                                         A device for changing the course (or flow) of a circuit. The prototypical model is a mechanical device (for example a railroad switch) which can be disconnected from one course and connected to another. The term “switch” typically refers to electrical power or electronic telecommunication circuits. In applications where multiple switching options are required (e.g., a telephone service), mechanical switches have long been replaced by electronic variants which can be intelligently controlled and automated. (source:

Hub                                                                                                                                                                                                                    A device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single segment. Hubs work at the physical layer (layer 1) of the OSI model. Hubs are either active or passive. Active hubs repeat the signal received at one port out each of the other ports (but not the original one). The device is thus a form of multiport repeater. Ethernet hubs are also responsible for forwarding a jam signal to all ports if it detects a collision.                   (source:

Click here to learn all about them in great detail at

Hubs, Switches, and Routers

September 18, 2006

Think of a hub as a splitter, splitting a single incoming line into multiple destination lines. The most common use for a hub is for small home or work networks. The problem with hubs is that they are practically brainless. Every time a packet of information is received by a hub, it is broadcast over all outgoing ports. This can lead to network congestion and packet collisions.

A switch is a hub taken to the next level. On the outside, a switch can appear cosmetically identical to a hub; it’s what’s on the inside that makes the difference. A switch has the ability to filter and send data to specific hardware ports. If a packet comes into the switch, it can choose the correct path rather than broadcasting it to the entire network and help eliminate network congestion. Switches also tend to offer advanced filter options, bandwidth metering, and traffic statistics.

A router is a piece of equipment that typically connects at least two networks and forwards packets the most efficient way based on its knowledge of the connected networks. Routers typically maintain routing tables that contain available route, distance, and network congestion information. The router uses these tables along with complex algorithms to determine the most efficient way to send a packet across the network.

For most home users with casual file transfers, a simple hub is sufficient. However, anyone transferring large amounts of data or using network-intensive applications should highly consider purchasing a switch. Users looking to run Internet Connection Sharing should consider purchasing a firewall/router combo.