Tim wrote:
On Mon, 2006-01-30 at 08:21 -0600, Les Mikesell wrote:
The distinction is fuzzy because there are some expensive devices
called 'layer 3 switches' that understand IP addresses and can
do some routing and filtering based on them. However what is
normally called a switch works at the network layer 2, using
only ethernet MAC addresses. They learn the hardware addresses
of the connected devices as packets are sent from them and once
a destination is known they will only forward packets to that
destination out the correct port.
Wouldn't they also have to be co-relating IPs to MAC addresses? Surely
they couldn't just work by the MAC, alone?
For instance if my PC at 192.168.1.1 wants to do something with
192.168.1.2, all that goes out on the wire is the IP addresses, hoping
that something else figures out how to connect the two together, or
hoping that they're already directly connected together.
Layer 2 switches don't care if the packet is NetBIOS, DECNet, Banyon
Vines, IP or IPX as long the packet is Ethernet. Every done at layer
2 is done with MAC addresses. IP is not involved.
The IP to MAC translations are done at the Layer 3 devices
(routers, PC's TCP/IP stack, etc.).
--
Linux Home Automation Neil Cherry ncherry@xxxxxxxxxxx
http://www.linuxha.com/ Main site
http://linuxha.blogspot.com/ My HA Blog
http://home.comcast.net/~ncherry/ Backup site
