Q1：
IP Network Numbers - Class A
Class A networks (0.x.x.x to 127.x.x.x) have an 8-bit network prefix with a 24-bit host number, and are also referred to as /8 networks.
The first bit is set to 0 to identify the network as a Class A type; this results in 128 (27) possible Class A networks, but those with prefix 0 and 127 are used for special functions and the upper half (with prefixes above 64) are reserved for future use.

IP Network Numbers - Class B
Class B networks (128.0.x.x to 191.255.x.x) have a 16-bit network prefix with a 16-bit host number, and are also referred to as /16 networks.
The first two bits of the prefix are set to 10, hence there are 214 (16384) possible Class B networks; currently around 12000 are defined (65%).

IP Network Numbers - Class C
Class C networks (192.0.0.x to 223.255.255.x) require 24 bits to identify the network, leaving 8 to identity the host, and are also referred to as /24 networks.
The first three bits of the network prefix are set to 110, hence there are 221 (2097152) possible Class C networks; currently around 800000 are defined (40%).

即使你ㄉIP Class相同，但IP區段與子網路遮罩不同還是無法連結。

Q2：
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class下Net開頭ㄉ四ㄍ登錄值內的所有設定值都砍掉，然後進入網路設定中，若已完全砍掉則離開，若還有殘餘亦砍掉，之後重新開機重新安裝所有通訊協定。

Q3：
哞還是覺得是你電腦本身設定ㄉ問題！因為中華電信帶去ㄉNoteBook測試是好ㄉ∼它就是好ㄉ！不要再設IPㄌ∼重新安裝好不要動任何設定值測試看看ㄅ。