Standard ACL

Standard access control list’s characteristic:

  • 1-99
  • host, network & subnet
  • all services are blocked
  • closest to destination
  • filter only source

Rules:
sequential order
all deny statements need to be given first, at least one permit statement set (mandatory)
implicit deny blocks all traffic by default where there’s no match
can have one ACL per interface, per direction
new entry, place to bottom of the list (to edit, need to use text editor because you cannot remove line by line)

*Wildcard mask: inverse mask (contrast to subnet mask)
tells router which portion of bits to match or ignore
0 indicates MUST MATCH (check bit)

Topology:

Capture

Implementation Guideline:
1. Create the ACL rules:
Ex.
R1(config)#access-list 15 deny 192.168.2.1 0.0.0.0
​R1(config)#access-list 15 deny 192.168.2.2 0.0.0.0
R1(config)#access-list 15 deny 192.168.3.0 0.0.0.255

R1(config)#access-list 15 permit any

2. Apply to interface:
R1(config)#interface Fa0/0

R1(config-if)#ip access-group 15 out

*Before testing it, make sure that all routing working well.

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