Goldfish Networks wordmark
IntermediatePublished 2026-08-14

CCNA Foundations: The IPv6 Default Route — One Route Out

Archive lab

Build a compact branch-to-edge topology that is dual-stack for IPv4 and intentionally incomplete for IPv6. IPv4 is fully working as a baseline. Your job: enable IPv6 forwarding on both routers, replace specific IPv6 routes at the branch with a single default (::/0) toward the edge, and add a specific IPv6 return route on the edge back to the branch LAN. Verify the branch host reaches the edge-side resources over IPv6 while the IPv4 plane remains stable.

Track
Est. time
55 minutes
Difficulty
Intermediate
Topics

Learning objectives

  • Enable and verify IPv6 forwarding on Cisco IOS routers
  • Configure an IPv6 default route (::/0) with a link-local next-hop on a point-to-point interface
  • Install a specific IPv6 return route on the upstream router to maintain asymmetric reachability
  • Validate end-to-end IPv6 connectivity from hosts and interpret the IPv6 routing table (gateway of last resort)

Troubleshooting focus

  • IPv6 forwarding disabled (ipv6 unicast-routing missing) prevents any L3 forwarding
  • Static default route missing or pointed at wrong next-hop/interface
  • Return route absent on the edge causes pings to fail one-way
  • Wrong prefix length (/127 or /65) on a LAN breaks SLAAC and reachability
  • Using a link-local next-hop without specifying the outgoing interface

Topology

Subscribe to preview this lab's topology.

See plans

Related labs

More hands-on Cisco Modeling Labs practice on the same track and topics.

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.

Create a free account to submit your lab for grading.

Create a free account
Found a problem with this lab?

Please sign in to report a problem — tying it to your attempts lets us reproduce and fix it faster.