diff --git a/School/Analyse/Layers/3. Network Layer.md b/School/Analyse/Layers/3. Network Layer.md
index 655e582..6998470 100644
--- a/School/Analyse/Layers/3. Network Layer.md	
+++ b/School/Analyse/Layers/3. Network Layer.md	
@@ -93,9 +93,20 @@ IPV4 are 4 byte integers. We use them in the following format:
 This is called a dotted decimal, each address contains 4 decimals of 8 bits (octets)
 Example: 00000000.00000000.00000000.00000000
 
-## Classful addresses
-Classfull addresses define 3 networks types
+### Classful addresses
+Classful addresses define 3 networks types
 
 Class A: First decimal shows the network ID, remaining 3 decimals show the host ID. (Large networks)
 
+Class B: First two decimals shows the network ID, remaining 2 decimals show the host ID. (Mid networks)
+
+Class C: First three decimals shows the network ID, remaining 1 decimal show the host ID. (Small networks)
+
+### Classless addresses
+In classless addresses the number of bits is used for a Network ID is given as a number after the address
+
+Example 144.24.13.172/**20 (20 bits used for network ID)**
+
+### Exceptions in IPV4
+![[exceptions-ipv4.png]]
 
diff --git a/exceptions-ipv4.png b/exceptions-ipv4.png
new file mode 100644
index 0000000..ba824a1
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