What are the two main frame forwarding methods used by Cisco switches?

Question

Accepted Answer

Store-and-forward receives the whole frame and checks the CRC before forwarding (catches errors, higher latency); cut-through forwards as soon as the destination MAC is read (lowest latency, no error check).

* Store-and-forward buffers the entire frame and validates the CRC before forwarding; cut-through forwards right after the destination MAC with no error check. *

Method
Description
Error Checking

Store-and-Forward
Receives the entire frame, computes CRC, then forwards if valid
Yes - checks CRC before forwarding

Cut-Through
Begins forwarding before the entire frame is received
No - no error checking

Store-and-Forward Process:

Receive entire frame into buffer
Compute CRC and compare to FCS field
If CRC is valid → look up destination MAC → forward
If CRC is invalid → discard frame

Cut-Through Process:

Read destination MAC address (first 6 bytes after preamble)
Begin forwarding immediately
No CRC validation performed

Go deeper:

Cut-through switching (Wikipedia) — the latency-versus-integrity trade-off against store-and-forward, plus the fragment-free variant.

Method	Description	Error Checking
Store-and-Forward	Receives the entire frame, computes CRC, then forwards if valid	Yes - checks CRC before forwarding
Cut-Through	Begins forwarding before the entire frame is received	No - no error checking