Open the lab

[ YOUR LAB FILE ]

Download the starting topology, then work through the lesson in SwitchLab.

Download SwitchLab Lab (.swlab)

  1. Save the .swlab file without renaming its extension.
  2. Open SwitchLab. Import and export controls currently require a desktop-width window. On a smaller screen, Tools → Fit brings the topology into view.
  3. Select Import Sandbox (folder icon), choose the downloaded file, and confirm the device and cable counts below.
  4. Select a device, then choose Open device on desktop or its name in the bottom bar on smaller screens. Select CLI for switches/routers or Desktop → Terminal for PCs. Enter enable only when the prompt ends in >.
  5. Follow this page beside the simulator. Use a free account to export your work. Reimport the original download to restart; export any work you want to keep first.

Prerequisites

  • Complete IPv4 addressing and static routing.
  • Recognize IPv6 hexadecimal addresses and /64 prefixes.

Follow the CCNA study path · Browse all SwitchLab labs

Topology

Repair an IPv6 LAN Prefix Mismatch: starting network imported into the SwitchLab sandbox.
Starting topology captured in SwitchLab. Select the image to view it at full size.

4 devices · 3 links

Scenario

IPv4 works across the branch network, but PC1 cannot reach its IPv6 gateway. R1’s LAN interface was entered in the wrong IPv6 prefix; the transit and route plan are correct.

Objectives

  • Verify IPv6 interface addressing and the host gateway relationship.
  • Prove IPv6 forward and return delivery independently of IPv4.

CCNA blueprint

200-301 v1.1 objectives — this lab covers the following specific skills, not every subtopic in the domain.

  • 1.8 — Configure and verify IPv6 addressing and prefixes.
  • 3.3 — Configure and verify IPv6 static routes.

Starting information

  • R1 g0/0: 2001:db8:10::1/64; R2 g0/0: 2001:db8:20::1/64. Hosts and IPv6 gateways are listed below.
  • Transit: R1 g0/1=2001:db8:12::1/64 and R2 g0/1=2001:db8:12::2/64.
  • Use a specific route to the remote /64 through the peer’s transit address. Preserve the IPv4 plan shown in the starter table.
  • These reserved documentation prefixes are for this isolated lab. IPv6 forwarding is configured separately from IPv4.
HostIPv4 addressMaskGateway
PC110.10.10.10255.255.255.010.10.10.1
PC210.20.20.20255.255.255.010.20.20.1
HostIPv6 addressPrefix lengthIPv6 gateway
PC12001:db8:10::10642001:db8:10::1
PC22001:db8:20::20642001:db8:20::1
RouterInterfaceIPv4 addressMask
R1g0/010.10.10.1255.255.255.0
R1g0/110.0.12.1255.255.255.252
R2g0/010.20.20.1255.255.255.0
R2g0/110.0.12.2255.255.255.252
Device / portDevice / port
PC1 / eth0R1 / g0/0
R1 / g0/1R2 / g0/1
PC2 / eth0R2 / g0/0

Tasks

  1. Inspect each PC’s ipconfig /all, each router’s show ipv6 interface brief and show ipv6 route, and baseline both address families.
  2. Find the LAN prefix mismatch on R1 and replace the incorrect interface address. Preserve the transit, static routes and host settings.
  3. Verify the intended connected /64 prefixes and each remote route. Check both ends; an outbound route alone does not provide a return path.
  4. From PC1 ping 2001:db8:20::20; from PC2 ping 2001:db8:10::10. Also verify the IPv4 control path, then save/export and reload.

Useful commands

show ipv6 interface brief
show ipv6 route
show running-config
copy running-config startup-config

Progressive hints

Hint 1

Use the working IPv4 network only as a physical-path control; it cannot prove the IPv6 configuration.

Hint 2

Compare each host’s /64 and gateway with its attached router interface, then inspect the remote route and next hop.

Hint 3

The remote IPv6 route on R1 uses next hop 2001:db8:12::2; R2 uses 2001:db8:12::1. R1’s LAN must be in 2001:db8:10::/64.

Verification

  • Both IPv6 host-to-host directions succeed.
  • The IPv4 control path also succeeds after completion.
  • The repaired or completed IPv6 interface and route configuration survives export/reload.

Solution / walkthrough

Show Solution

Use enable only from a > prompt; if already at #, begin with configure terminal.

R1

Use the approved documentation prefixes and directly reachable IPv6 next hop. IPv4 and IPv6 route tables are independent; verify both when the task requests dual stack.

enable
configure terminal
interface g0/0
no ipv6 address 2001:db8:99::1/64
ipv6 address 2001:db8:10::1/64
exit
end
copy running-config startup-config

Run every verification check above after the changes. A saved configuration alone does not prove packet delivery.

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Build IPv6 Static Routing between Two Sites

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