The principle of routing access control list and the detailed explanation of three types

Detailed explanation of the principle of routing access control list

A routing access control list (ACL) is a list of instructions (that is, rules) applied to a router interface to tell the router which packets can be received and which packets need to be rejected.

ACL can be divided into three types

Standard ACL: check the source address of the packet. Use a number between 1 and 99 as the list number.

Extended ACL: checks both the source and destination addresses of the packet. Use a number between 100 and 199 as the list number.

Named ACL: named ACL allows you to use names instead of list numbers in standard and extended ACL.

The following examples are used to introduce the use of these three methods.

Standard ACL experimental topology diagram

Create a standard ACL so that C1 cannot access C3 C2 and can be accessed properly

R1 (config) # access-list 1 deny 192.168.1.2 255.255.255.0 create an access control list

R1 (config) # int f0bin0

R1 (config-if) # ip access-group 1 in applies ACL to the interface

R1 (config-if) #

As you can see in the following figure, ACL has been applied, PC1 cannot access PC3 and PC2 is normal.

Extended ACL Experimental Topology Diagram

Allow C1 to access the www service of the C2 server and deny other services

Verification

Named ACL experimental topology diagram

Allow C1 to access the www service of the C2 server and deny other services

Custom naming