Switching Switching – A Process of using the MAC address on LAN is called Layer 2 Switching. Layer 2 Switching is the process of using hardware address of devices on a LAN to segment a network. Switching breaks up large collision domains into smaller ones and that a collision domain is a network segment with two or more devices sharing the same bandwidth. Ethernet is a LAN technology based on the IEEE 802.3 standard. It provides a shared medium to transfer the data.
There are three Switching Modes 1. Cut through (Fast Forward)- When in this mode, the switch only waits for the destination hardware address to be received before it looks up the destination address in the MAC filter table. Cisco sometimes calls this the fast forward method. 2. Fragment Free (Modified cut through)- This is the default mode for the catalyst 1900 switch, and it’s sometimes referred to as modified cut through. In fragment free mode, the switch checks the first 64 bytes of a frame before forwarding it for fragmentation, thus guarding against forwarding runts, which are caused by collisions. 3. Store and forward- In this mode the complete data frame is received on the switch’s buffer, a CRC is run, and if the CRC passes, the switch looks up the destination address in the MAC filter table. We always use Store and forward switch.
Figure 1 Switching
Modes
Functions of a Switch 1. Address Learning- A switch learns MAC address based on Source MAC.