How does a standard ACL differ from an extended ACL?

#Standard ACL

Standard ACL is a simple access control list that filters traffic only by the source IP address.

#What it takes into account:

• only the source IP (where the traffic came from)

#What it does not take into account:

• the destination IP address;
• the protocol (TCP/UDP/ICMP);
• ports.

#Characteristics:

• simple to configure;
• coarse filtering;
• can block extra traffic.

It is usually placed closer to the destination, so it does not cut off needed traffic too early.

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#Extended ACL

Extended ACL is an advanced access control list that filters traffic by many parameters.

#What it takes into account:

• the source IP address;
• the destination IP address;
• the protocol (TCP, UDP, ICMP and others);
• port numbers.

#Characteristics:

• very flexible;
• allows precise access control;
• most often used in real networks.

It is usually placed closer to the source, so it can block unwanted traffic right away.

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#The main difference (table)

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#A simple example

• Standard ACL:

  "Allow or deny everything from this computer"

• Extended ACL:

  "Allow this computer access only to this server on this port"