Question: what is flsm vlsm and cidr?
Answer: FLSM and VLSM. That brings us to Fixed Length Subnet Masks (FLSM) and Variable Length Subnet Masks (VLSM). FLSM and VLSM refer to how IP address space is assigned within each organization. By comparison, the terms we described above (Classful and CIDR) refer to how IP address space is allocated from IANA/RIRs.