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.).