Subnet help?

[vivahop]

Cacs bac oi, bac nao thao ve subnetting co' the dua mot vi du va` cach tinh subnet va valid host address cua lop a,b hoac c khong ah.
Thanks nhieu.
Em ko duoc hoc co ban nen sau khi tim duoc subnet address thi chang hieu tinh cac khoang host address nhu the nao va` buoc nhay gi` do'.