Lab Simulation 3 Guidelines This is a lab item in which tasks will be performed on virtual devices. - Refer to the Tasks tab to view the tasks for this lab item. - Refer to the Topology tab to access

Lab Explanation: Dual-Stack (IPv4 + IPv6) Router Configuration Overall Goal The task establishes a dual-stack link between R1 and R2 using their Ethernet0/1 interfaces. "Dual-stack" means each interface carries both an IPv4 and an IPv6 address simultaneously - a common real-world

Submitted by olafpl· Mar 5, 2026Network Fundamentals

Question

Lab Simulation 3 Guidelines This is a lab item in which tasks will be performed on virtual devices. - Refer to the Tasks tab to view the tasks for this lab item. - Refer to the Topology tab to access the device console(s) and perform the tasks. - Console access is available for all required devices by clicking the device icon or using the tab(s) above the console window. - All necessary preconfigurations have been applied. - Do not change the enable password or hostname for any device. - Save your configurations to NVRAM before moving to the next item. - Click Next at the bottom of the screen to submit this lab and move to the next question. - When Next is clicked, the lab closes and cannot be reopened. Topology Tasks Configure IPv4 and IPv6 connectivity between two routers. For IPv4, use a /28 network from the 192.168.180.0/24 private range. For IPv6, use the first /64 subnet from the 2001:0db8:acca::/48 subnet. 1. Using Ethernet0/1 on routers R1 and R2, configure the next usable /28 from the 192.168.180.0/24 range. The network 192.168.180.0/28 is unavailable. 2. For the IPv4 /28 subnet, router R1 must be configured with the first usable host address. 3. For the IPv4 /28 subnet, router R2 must be configured with the last usable host address. 4. For the IPv6 /64 subnet, configure the routers with the IP addressing provided from the topology. 5. A ping must work between the routers on the IPv4 and IPv6 address ranges. Answer: R1 enable configure terminal ipv6 unicast-routing interface ethernet0/1 ip address 192.168.180.17 255.255.255.240 ipv6 address 2001:db8:acca::1/64 no shutdown end copy running-startup config R2 enable configure terminal ipv6 unicast-routing interface ethernet0/1 ip address 192.168.180.30 255.255.255.240 ipv6 address 2001:db8:acca::2/64 no shutdown end copy running-startup config

Exhibits

Explanation

Lab Explanation: Dual-Stack (IPv4 + IPv6) Router Configuration

Overall Goal

The task establishes a dual-stack link between R1 and R2 using their Ethernet0/1 interfaces. "Dual-stack" means each interface carries both an IPv4 and an IPv6 address simultaneously - a common real-world design during the IPv4-to-IPv6 transition. The correct approach is to calculate the right subnets first, then assign addresses to each router, enable the interfaces, and save.

Step-by-Step Reasoning

Subnetting Math (do this before touching any router)

IPv4 - Finding the next /28:

A /28 mask = 255.255.255.240. Each /28 block has 16 addresses (14 usable hosts).

Subnet #	Network Address	Usable Range	Broadcast
1st	192.168.180.0	.1 - .14	.15
2nd	192.168.180.16	.17 - .30	.31
3rd	192.168.180.32	.33 - .46	.47

Since 192.168.180.0/28 is unavailable, the next usable subnet is 192.168.180.16/28.

R1 gets the first usable host: .17
R2 gets the last usable host: .30

IPv6 - Finding the first /64:

The parent prefix is 2001:0db8:acca::/48. Subnetting to /64 means the 4th hextet becomes the subnet ID. The first /64 is simply 2001:db8:acca:0000::/64, written as 2001:db8:acca::/64. R1 and R2 get ::1 and ::2 within that subnet.

R1 Configuration

enable                          # Enter privileged EXEC mode
configure terminal              # Enter global config mode
ipv6 unicast-routing            # Enable IPv6 routing (off by default on IOS)
interface ethernet0/1           # Select the correct interface
 ip address 192.168.180.17 255.255.255.240   # First usable host in .16/28
 ipv6 address 2001:db8:acca::1/64            # First host in the /64
 no shutdown                    # Bring the interface up (default is shutdown)
end
copy running-config startup-config           # Persist to NVRAM

R2 Configuration

enable
configure terminal
ipv6 unicast-routing
interface ethernet0/1
 ip address 192.168.180.30 255.255.255.240   # Last usable host in .16/28
 ipv6 address 2001:db8:acca::2/64
 no shutdown
end
copy running-config startup-config

Why Each Step Matters

Step	Why It's Necessary	What Breaks If Skipped
`ipv6 unicast-routing`	IOS routers do not forward IPv6 packets by default	IPv6 addresses can be assigned but traffic won't route; pings fail
`ip address` with correct mask	Places the interface in the right subnet	If masks differ between routers, they're in different subnets and can't communicate
`ipv6 address`	Assigns the link-local + global unicast address	No IPv6 connectivity, ping6 fails
`no shutdown`	Ethernet interfaces default to administratively down	Interface stays down; no traffic passes even with correct addressing
`copy running-config startup-config`	Writes RAM config to NVRAM	Config is lost on reload - the exam checks saved config

Order matters: You must enter interface config mode before assigning addresses, and no shutdown must come after the address is assigned so the interface comes up cleanly.

Common Mistakes

Using .16 or .31 as a host address - those are the network and broadcast addresses, not usable hosts.
Forgetting ipv6 unicast-routing - this is the single most common reason IPv6 pings fail on IOS.
Wrong subnet - assigning from the first /28 (.0) instead of the second (.16) fails because that block is unavailable/already used.
copy running-startup config (typo in original answer) - the correct command is copy running-config startup-config.

Memory Tip

"Next block, first/last, save it."

Next block = skip the unavailable /28, use the next one

First host to R1, last host to R2 = alphabetical order (R1 -> first, R2 -> last)

Save it = copy run start before clicking Next or the config is gone

For IPv6: expanding 2001:0db8:acca::/48 to /64 just adds a fourth group of zeros - the first subnet is always ::0000::/64, so hosts start at ::1.

Topics

#IPv4 addressing#IPv6 addressing#Subnetting#Router interface configuration

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