Store-and-forward switching is one of three primary types of LAN switching. With the store-and-forward switching method, the LAN switch copies the entire frame onto its onboard buffers and computes the cyclic redundancy check (CRC). Because it copies the entire frame, latency through the switch varies with frame length.
The frame is discarded if it contains a CRC error, if it's too short (less than 64 bytes including the CRC), or if it's too long (more than 1,518 bytes including the CRC). If the frame doesn't contain any errors, the LAN switch looks up the destination hardware address in its forwarding or switching table and determines the outgoing interface. It then forwards the frame toward its destination.
FragmentFree is a modified form of cut-through switching in which the switch waits for the collision window (64 bytes) to pass before forwarding. If a packet has an error, it almost always occurs within the first 64 bytes. FragmentFree mode provides better error checking than the cut-through mode, with practically no increase in latency.
The Port Aggregation Protocol (PAgP) is used to add more features to the EtherChannel technology. This protocol is used to learn the capabilities of the neighbors' EtherChannel ports. By doing this, it allows the switches to connect via Fast EtherChannel automatically.
The PAgP protocol groups the ports that have the same neighbor device ID and neighbor group capability into a channel. This channel is then added to the Spanning Tree Protocol as a single bridge port.
Proxy Address Resolution Protocol (Proxy ARP) is a variation of the ARP protocol in which an intermediate device, such as a router, sends an ARP response on behalf of an end node to the requesting host.
- No need to configure clients with a gateway
- Load balancing, although this is somewhat random
- Immediate fault tolerance for addresses not recently contacted