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Introduction network components

Physical network

A physical network consists of 2 or more connected computers. They communicate directly without address-translating devices like routers and firewalls.
Connected computers within a physical network cannot communicate if they belong to different logical networks.

Logical networks

A logical network is defined by it's network address and the network mask.
With a known host address and the network mask, the network mask can be derived by simply AND-ing the host-address and the mask.
All hosts sharing the same network address and network mask are in the same logical network.
Computers within the same logical network can only communicate if there is a physical path (possibly through switches, bridges, routers, or firewalls).

IP address

IP address is a 32 bit address (or 48 bit in IPv6), giving each host (or router, firewall, ...) a unique number within the logical network.

A network address is the result of AND-ing any host-address of a network with the network mask, giving the lowest possible host address in the network.

One (or more) IP addresses can be assigned to a ethernet card of a computer, thus making the computer member of one (or more) logical networks.
This IP address is then used to route on and between logical networks.

MAC address

A MAC address is a unique address of an ethernet card. These usually cannot be changed, and (more ore less) guaranteed to be unique over the world. However, the MAC address in the Edimax can be changed.
Each physical connector has exactly 1 MAC address.

Switch

A switch connects physical networks (or single hosts) by use of MAC-address.

It learns on which port to find a MAC address by maintaining a table.
A switch has its own MAC address, because it is part of a physical network.
It has no IP address, because it is not part of a logical network.

Bridge

A bridge connects 2 parts of a physical network, just as a transparant wire. It has no IP- or MAC address of its own.
It only passes packets if needed, so it can decrease bandwith and collisions between the 2 parts of a single network.

Router

A router connects 2 or more logical networks. It must have an IP address in each logical network it is connected to.
Each IP address can be assigned to a separate connector, resulting in a physical wire for each ogical network.
However, assigning more IP addresses to a single ethernet port results in several logical networks running over a single physical network.

Firewall

A firewall routes IP packets as a router. However, it decides if packets must be passed or dropped by inspecting packet-type, port number, source and destination IP address.
It has no IP or MAC address of its own, but it is merely a program in the Operating System of a computer, deciding how the router should work.

Meaning of the colours:	New or changed text since last visit (see user settings at top of page).
	Edimax stands for the BR-6104KP with USB
	Sweex means LB000021 and compatibles without USB.
	white text is part of a file on disk.

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