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Spelling: Router
See also: Hub [1], Switch [2], Routing [3]
A ROUTER IS AN INTELLIGENT DEVICE THAT LINKS TWO OR MORE COMPUTER
NETWORKS TOGETHER.
Generally (see note below) this means that it links two subdivisions
or Subnets [4] of a TCP/IP network together.
A router can be a dedicated device or it can be a normal PC with two
or more network cards. It operates a bit like a postal exchange.
Network data is sent as PACKETS. Each packet contains information as
to its destination. A router will read the destination of every packet
it receives and work out where to send it. It does this by consulting
its ROUTING TABLE. The Routing Table is a list of destination network
addresses and/or subnets. In this list each destination is
cross-referenced to one of the router's network interfaces and the
address of the next router on the path to that destination. The router
does not "know" the entire delivery path or ROUTE of the data. It
simply "knows" that by sending the data to the appropriate interface
it will get to its destination.
Routers often have a DEFAULT ROUTE (sometimes called a DEFAULT
GATEWAY) in their Routing Tables. If the router receives a packet that
is destined for an address that is not in its Routing Table, the
router will send that packet to the DEFAULT GATEWAY, if it has one. If
the router does not have Default route and it does not "know" where to
send the packet, it will send a _Destination Host Unreachable_ or
similar message back to the sender.
If you run Windows [5] you can control your routes using the _route_
command at a DOS prompt. _route print_ will show your routing table.
If you run Linux you should be able to control your routes using
_route_ or _ip_. Issuing a _route_ or _ip r_ at the command prompt
should show your routing table.
Broadband [6] or ADSL [7] Routers are common examples of routers
designed for the home market. They allow you to run a home Local Area
Network [8] and let any device on that LAN access your Broadband
Internet connection. Broadand Routers usually also have Firewall [9]
and other capabilities
NOTE: A device that links two parts of a network together that are
physically different medium eg FibreOptic [10] and Cat5 [11] Ethernet
[12] or Cat5 [13] and 802.11b [14] Ethernet is generally not
considered to be a Router unless it also routes traffic between two
networks or Subnets [15]. A device that links two or more network
protocols (such as TCP/IP [16], IPX [17] or AppleTalk [18]) is these
days known as a Gateway [19].
Links:
------
[1] http://melbournewireless.org.au/?Hub
[2] http://melbournewireless.org.au/?Switch
[3] http://melbournewireless.org.au/?Routing
[4] http://melbournewireless.org.au/?Subnet
[5] http://melbournewireless.org.au/?Windows
[6] http://melbournewireless.org.au/?Broadband
[7] http://melbournewireless.org.au/?ADSL
[8] http://melbournewireless.org.au/?LAN
[9] http://melbournewireless.org.au/?Firewall
[10] http://melbournewireless.org.au/?FibreOptic
[11] http://melbournewireless.org.au/?Cat5
[12] http://melbournewireless.org.au/?Ethernet
[13] http://melbournewireless.org.au/?Cat5
[14] http://melbournewireless.org.au/?802.11b
[15] http://melbournewireless.org.au/?Subnet
[16] http://melbournewireless.org.au/?TCPIP
[17] http://melbournewireless.org.au/?IPX
[18] http://melbournewireless.org.au/?AppleTalk
[19] http://melbournewireless.org.au/?Gateway
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