Part 20 lab, Standard ACLs Configuration

Описание: Everything was working.

NAT translations? ✅
Internet access? ✅
OSPF neighbors? ✅

Then one ACL was applied…

And the network silently collapsed.

In this deep-dive lab, I break down how Access Control Lists (ACLs) interact with:

NAT (PAT Overload)

OSPF (Routing Protocol 89)

VLAN segmentation (10 / 20 / 30)

Real Cisco CLI configuration

🔥 What you’ll learn:

✔ What an ACL really does
✔ Standard vs Extended ACL (and why standard can be dangerous)
✔ Why NAT changes ACL design
✔ Why OSPF MUST be explicitly permitted
✔ Correct interface placement (Inbound LAN side)
✔ Packet processing order:
ACL → Routing → NAT → Exit

Most engineers forget this:

OSPF is NOT TCP.
OSPF is NOT UDP.
It’s protocol 89.

Block it once…
And your routing adjacency dies instantly.

This lab demonstrates:

• Allow VLAN 10 & 30
• Block VLAN 20
• Keep NAT working
• Keep OSPF stable

And most importantly…

How to design ACLs without breaking your entire infrastructure.

If you're serious about:
Cybersecurity 🔐
Enterprise Networking 🌐
Cloud Architecture ☁️
AI Infrastructure 🤖

Then mastering ACL logic is mandatory.

Because in real networks…

Failure is silent.

#CyberSecurity #Networking #CCNA #Cisco #AccessControlList #NAT #OSPF #CloudComputing #AIInfrastructure #NetworkEngineer #ITSecurity #RoutingAndSwitching #TechEducation