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  • ACL Access Control List practical in cisco packet tracer

     

     

    ACL Access Control List practical in cisco packet tracer

     

     

    🔐 ACL (Access Control List)



    ACL is a set of rules used on routers and switches to permit or deny network traffic based on IP addresses, protocols, or ports.



    ACL is used for:

    • Security
    • Traffic filtering
    • Blocking users
    • Allowing specific networks
    • Firewall-like control


    Used in:

    • Enterprises
    • Firewalls
    • ISPs
    • Corporate networks
    • Banks



    🎯 Real-Life Example



    Suppose company says:

    ❌ HR department cannot access Server
    ✅ IT department can access Server

    👉 ACL handles this.


     

    🔥 What You Will Learn


    ✔ Permit/Deny traffic
    ✔ Standard ACL
    ✔ Extended ACL basics
    ✔ Interface filtering
    ✔ Inbound/Outbound traffic
    ✔ Enterprise security logic



    🧪 Practical Topology



    In Cisco Packet Tracer create:

    PC0 ---- Switch ---- Router ---- Server



    🌐 IP Addressing





    🔌 Wiring




    Use:
    ✅ Copper Straight-Through

     

     

     ⚙️ Step 1: Configure Router Interfaces

     

     

    enable
configure terminal

interface g0/0
ip address 192.168.1.1 255.255.255.0
no shutdown

interface g0/1
ip address 200.1.1.1 255.255.255.0
no shutdown

     

     

     


     

     

     

     ⚙️ Step 2: Configure PC & Server

     

     


     


    🧪 Step 3: Test Before ACL



    From PC0:
    ping 200.1.1.2
    ✔ Success






    🔥 Step 4: Create ACL


    Now we block PC0 from reaching Server.

    🔹 Create Standard ACL 


    access-list 1 deny 192.168.1.10
access-list 1 permit any


    🧠 Meaning





    🔥 Step 5: Apply ACL to Interface



    Apply on router interface:

    interface g0/0
    ip access-group 1 in





    🧠 Important Concept


    in means:

    Traffic entering interface.



    🔍 Packet Flow



    PC0 → Router G0/0 → ACL checks → deny
    Packet dropped.


    🧪 Step 6: Test Again



    From PC0:
    ping 200.1.1.2
    ❌ Failed
    ACL blocked it.

      

     

     


     

     

     

    🔥 Verify ACL


    Run:
    show access-lists
    You’ll see packet matches.








    🔥 Full ACL Configuration


    enable
configure terminal

access-list 1 deny 192.168.1.10
access-list 1 permit any

interface g0/0
ip access-group 1 in








    🧠 VERY IMPORTANT RULE



    ACL processes:

    TOP → DOWN

    First match wins.

    🔥 Hidden Rule

    Every ACL ends with:

    implicit deny any

    Means:
    If not permitted → automatically denied.



    🎯 Standard vs Extended ACL




    🔥 Example Extended ACL


    access-list 101 deny tcp 192.168.1.0 0.0.0.255 any eq 80



    Blocks:

    HTTP traffic

     

    🧠 Important Interview Questions


    ❓ What is ACL?

     Traffic filtering/security mechanism.


    ❓ What is implicit deny?
    Hidden deny rule at end of ACL.




    ❓ Difference between inbound and outbound?




    ❓ Which ACL is closer to destination?
    Standard ACL


    ❓ Which ACL is closer to source?
    Extended ACL


    Disclaimer



    All tutorials are for informational and educational purposes only and have been made using our own routers, servers, websites and other vulnerable free resources. we do not contain any illegal activity. We believe that ethical hacking, information security and cyber security should be familiar subjects to anyone using digital information and computers. Hacking Truth is against misuse of the information and we strongly suggest against it. Please regard the word hacking as ethical hacking or penetration testing every time this word is used. We do not promote, encourage, support or excite any illegal activity or hacking.




     

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