Standard ACLs are configured on routers to permit or deny traffic based on source IP addresses. The ACL number must be between 1-99 or 1300-1999. The ACL is applied to an interface using the ip access-group command with the in or out keyword to specify the traffic direction. For example, an ACL can permit traffic from a management LAN subnet to a server, and the ACL would be applied to the incoming interface using the "in" keyword.

1. Configuring standard ACLs
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2.  To create an standard access list, the following command
is used from the router's global configuration mode:
 R1(config)# access-list ACL_NUMBER permit|deny IP_ADDRESS
WILDCARD_MASK
 ACL number for the standard ACLs has to be between 1–99 and
1300–1999.
 You can also use the host keyword to specify the host you want to
permit or deny:
 R1(config)# access-list ACL_NUMBER permit|deny host
IP_ADDRESS
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3.  Once the access list is created, it needs to be applied to an
interface.
 You do that by using the ip access-group ACL_NUMBER
in|out interface subcommand.
 in and out keywords specify in which direction you are
activating the ACL.
 in means that ACL is applied to the traffic coming into the
interface, while the out keyword means that the ACL is applied
to the traffic leaving the interface.
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4. Consider the following network topology:
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5.  We want to allow traffic from the management LAN to the server
S1. First, we need to write an ACL to permit traffic from LAN
10.0.0.0/24 to S1. We can use the following command on R1:
 The command above permits traffic from all IP addresses that
begin with 10.0.0. We could also target the specific host, by using
the host keyword:
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6.  The command above permits traffic only from the host with the
IP address of 10.0.0.1.
 Next, we need to apply the access list to an interface. Since the
traffic is entering the interface on R1, we need to use
the in keyword:
 NOTE - at the end of each ACL there is an implicit deny all
statement. That means that all traffic not specified in earlier
ACL statements will be forbidden.
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