Which access methods and topologies are used for 10/40/100 Giga Ethernet? So I'm learning about different Ethernet types and it's stated that the Standard Ethernet operates at Bus/Star and uses CSMA/CD as an access method. The same is stated for Fast Ethernet and Giga Ethernet minus the Bus part. I was wondering about 10/40/100 Giga Ethernets? I have looked everywhere but couldn't find a single clue except "All Gigabit Ethernet variants use a star topology" regarding the topologies. Is it safe to assume that these are considered Gigabit variants? and what about the access methods? I can't imagine they're using CSMA/CD because it sounds like they've started moving towards full-duplex mode at Giga Ethernet

CSMA/CD is obsolete. It was only used with 10 and 100 Mbit/s Ethernet. CSMA/CD was specified for Gigabit Ethernet as well but wasn't used anywhere. All modern variants use full-duplex, point-to-point links without requiring a channel access method or creating collision domains.

Also, all modern variants (except for PON variants) use point-to-point links, requiring switches for connecting more than two nodes. A single switch arranges the attached nodes in a star topology and multiple switches are connected in a tree topology. Chains or rings are also possible using a spanning tree protocol, but less optimal.