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7.0 ACCESS CONTROL LIST (ACL OPERATION (PURPOSE OF ACLs (ACL Operation…

- - - - A series of IOS commands that control
        whether a router forwards or drops
        packets based on information found
        in the packet header.
    - - Packet filtering controls access to a network by
        analyzing the incoming and outgoing packets and
        forwarding them or discarding them based on given
        criteria.
    - - Outbound
        ACLs
        
        Incoming packets are routed to the outbound
        interface and then they are processed
        through the outbound ACL.
      - Inbound
        ACLs
        
        Incoming packets are processed
        before they are routed to the
        outbound interface.
  - - - A string of 32 binary digits used by
        the router to determine which
        bits of the address to examine for a match.
    - - Wildcard Masks
        to Match IPv4 Subnets
      - Wildcard Masks
        to Match Ranges
    - - Calculating wildcard masks can be
        challenging. One shortcut method is to
        subtract the subnet mask from
        255.255.255.255.
  - - - Rules for
        Applying
        ACLs
        
        One ACL per direction
        
        One ACL per interface
        
        One ACL per protocol
      - Meaning
        
        To manage the type of traffic allowed
        to enter or exit that interface.
  - - - Meaning
        
        Every ACL should be placed where
        it has the greatest impact on efficiency.
      - Rules
        
        Extended
        ACLs
        
        Locate extended ACLs as close as
        possible to the source of the traffic
        to be filtered.
        
        Standard
        ACLs
        
        Because standard ACLs do not specify
        addresses, place them as close
        to the destination as possible.
- - - - A standard ACL with a number in the range of 1 through 99.
    - - After a standard IPv4 ACL is configured,Use the ip access-group command in interface configuration mode.To remove an ACL from an interface, first enter the no ip access-group command on the interface, and then enter the global no access-list command to remove the entire ACL.
    - - Naming an ACL makes it easier to understand its function. When identify ACL with a name instead of with a number, the configuration mode and command syntax are slightly different.
      - Capitalizing ACL names is not required, but makes them stand out when viewing the running-config output.
  - - - To create or edit the ACL and then paste it into the router interface. For an existing ACL, use the show running-config command to display the ACL, copy and paste it into the text editor, make the necessary changes, and paste it back in to the router interface.
    - - Sequence numbers were used to edit
        a standard numbered IPv4 ACL. Individual
        statements can easily be inserted or deleted.
    - - Also be used to edit standard named ACLs. In named access list configuration mode, use the no sequence-number command to quickly delete individual statements.