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BeginnerPublished 2026-07-13

CCNA Foundations: Standard ACLs — Filter Traffic by Source

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Build a compact two-router, three-host topology. Implement a numbered standard ACL on the destination router to permit Client-A and deny Client-B from reaching a protected server based solely on source subnet. Verify from the end hosts that permitted traffic succeeds and denied traffic fails, and practice correct ACL placement and direction.

Track
Est. time
40 minutes
Difficulty
Beginner
Topics

Learning objectives

  • Author a numbered standard ACL (1–99) that matches traffic by source network only
  • Place a standard ACL on the interface closest to the destination in the correct direction
  • Verify ACL behavior from end hosts and interpret counters
  • Differentiate standard vs. extended ACL use cases and placement

Troubleshooting focus

  • CLIENT-B still gets replies from 10.30.30.10: the ACL is on the wrong interface or the wrong direction.
  • The deny line in show access-lists 10 never increments while CLIENT-B pings: check the wildcard mask — for a /24 it is 0.0.0.255, not a subnet mask — and that the permit and deny lines are not reversed.
  • This lab includes it deliberately.
  • Both clients behave inconsistently and the ACL looks right: fix routing first. show ip route on both routers must list all three LANs; ACLs should never mask a routing problem.

Topology

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Grade your work

How this lab is graded
  • Build it your way. Where a lab lets you choose a value — a VLAN name, an interface description — grading checks that you configured it, not which name you picked. Names that another line has to reference, like an ACL applied with access-class, are stated in the guide and do have to match.
  • Addresses, modes and protocol keywords are exact. An IP address, a subnet mask, switchport mode trunk, an encapsulation — these carry the meaning of the lab, so they are graded as written in the guide.
  • Grading reads your saved configuration. Export the lab from CML after you have configured it, and make sure anything you set is in the running-config — a change that only exists in a terminal session never reaches the grader.
  • You can submit as many times as you like. Your best score stands, and each attempt tells you which checks passed so you can work the gaps.
  • Scored something you believe is correct? Use Report an issue on this page — that is exactly how the grading fixes in the changelog got found.

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