Security Fundamentals Foundational ~6 min

Write a standard numbered ACL

On router R1, build standard access list 10 with two entries:

Then confirm with show access-lists.

Topology

Objectives

Hint 1, syntax

access-list <num> permit|deny <source>. Standard ACLs are numbered 1-99. Use host X.X.X.X for a single host and X.X.X.0 0.0.0.255 for a /24.

Hint 2, order matters

ACLs match top-down; put the more specific rule (the host permit) BEFORE the broader deny, or the host permit never gets evaluated.

Hint 3, full sequence

enable
configure terminal
 access-list 10 permit host 192.168.1.100
 access-list 10 deny 192.168.1.0 0.0.0.255
 end
show access-lists

Bonus, the named alternative

Real IOS also supports named standard ACLs. Same semantics, easier to read:

configure terminal
 ip access-list standard MGMT-HOSTS
  permit host 192.168.1.100
  deny 192.168.1.0 0.0.0.255
  exit
 end

Blueprint 5.6 requires both forms.

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