ACL - Access Control Lists

ACL - Access Control Lists

1. Definition

   • Series of IOS commands that control whether a router forwards or drops packets based on information found in the packet header.

2. Function

   • Set of rules that give added control for packets
     • Inbound ACLs
       • Incoming packets are processed before they are routed to the outbound interface.
     • Outbound ACLs
       • Incoming packets are routed to the outbound interface, and then they are processed through the outbound ACL.

3. Characteristics

   • Limit network traffic to increase network performance
   • Provide traffic flow control
   • Provide a basic level of security for network access
   • Filter traffic based on traffic type.
   • Screen hosts to permit or deny access to network services.

4. Standard ACLs

   • Filter IP packets only according to the address of origin[1]

5. Extended ACLs

   • Filter IP packets according to different attributes [1]
     • IP addresses of origin and destination [1]
     • TCP and UDP ports of origin and of destiny [1]
     • Types of protocol (IP, ICMP, UDP, TCP or number of protocol) [1]

6. Wildcard Masking

   • It's an amount of 32 bits.A bit of mask 0 wildcard means "check the bit value corresponding "and a bit 1 of a mask wildcard means "do not check (ignore) the bit value corresponding ". [2]

7. Complexes ACLs

   • Dynamics[3]
     • They use a mechanism basic authentication for activate the ACL.[3]
   • Reflectives[3]
     • They are a type of firewall primitive that allows the traffic only if it is started in a address [3]
   • Based on times[3]
     • are activated in dates and times that established previously. [3]

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