We went from a class C network to Class B. In AD Sites and Services I had added the new subnet and deleted the old one. We have 2 subnets total. Now I see an additional subnet (a third one) that I did not create with the same network IP that I created, except that the subnet has a string of hexadecimal numbers after it. Example: 172.20.0.0/16CNF:acbbc99-30b3-49bd-bab6-b6ba361b9020 Any idea what that is?

That object was created due to a "collision". Apparently you and/or someelse created the object with the same "name" while connected to two different DCs, within the same replication cycle. You can safely delete it. Visit: anITKB.com, an IT Knowledge Base.