Practical 7: VLAN Configuration & IPv6 Subnetting

TechNova has been assigned the prefix:

• IPv6 Prefix: 2001:DB8:CAFE::/48
• Prefix Length: /48 (first 48 bits are fixed)
• Required Subnets: 4 (one per department)

Step 1 — Understand the /48 prefix

With a /48 prefix, the address is structured as:

• First 48 bits (3 hextets): Global Routing Prefix — fixed by the ISP (2001:DB8:CAFE)
• Bits 49–64 (4th hextet): Subnet ID — you control this
• Last 64 bits (hextets 5–8): Interface ID — host addresses (never change for subnetting)

Step 2 — How many subnets can we create?

Fill in the answers below:

Question	Your Answer
Subnet ID bits (64 − 48)
Total possible /64 subnets (2?)
Hosts per /64 subnet (264)

✔ Check

Step 3 — Assign subnet IDs

We need 4 subnets — one for each department. Simply count up in the 4th hextet (0001, 0002, 0003, 0004). Fill in the network addresses:

✔ Check Subnets

IPv4 addressing plan

TechNova also uses IPv4 (dual-stack). For simplicity, each department gets a /24 subnet:

VLAN	Department	IPv4 Network	Subnet Mask
10	Engineering	192.168.10.0	255.255.255.0
20	Sales	192.168.20.0	255.255.255.0
30	Finance	192.168.30.0	255.255.255.0
40	IT Support	192.168.40.0	255.255.255.0

Open Packet Tracer and build the following topology.

Equipment

• 1 × Router — 2911
• 1 × Switch — 2960-24TT
• 8 × PC — (2 per department)

Cabling

1. Place the Router at the top of the workspace.
2. Place the Switch below the router.
3. Connect the router GigabitEthernet0/0 to the switch GigabitEthernet0/1 using a Copper Straight-Through cable.
4. Arrange 8 PCs in 4 pairs below the switch. Label them PC1–PC8.
5. Connect each PC (FastEthernet0) to the switch using Copper Straight-Through cables:
   • PC1 → Fa0/1  |  PC2 → Fa0/2   (Engineering — VLAN 10)
   • PC3 → Fa0/3  |  PC4 → Fa0/4   (Sales — VLAN 20)
   • PC5 → Fa0/5  |  PC6 → Fa0/6   (Finance — VLAN 30)
   • PC7 → Fa0/7  |  PC8 → Fa0/8   (IT Support — VLAN 40)

Click on the Switch, go to the CLI tab, and enter the following configuration. This creates 4 VLANs, assigns PC ports to the correct VLAN, and configures the trunk link to the router.

Part A — Create VLANs

enable
configure terminal
hostname TechNova-SW
!
vlan 10
 name Engineering
vlan 20
 name Sales
vlan 30
 name Finance
vlan 40
 name IT_Support

• vlan 10 — creates VLAN 10.
• name Engineering — gives the VLAN a descriptive label so administrators can easily identify its purpose.

Part B — Assign access ports

interface range FastEthernet0/1-2
 switchport mode access
 switchport access vlan 10
!
interface range FastEthernet0/3-4
 switchport mode access
 switchport access vlan 20
!
interface range FastEthernet0/5-6
 switchport mode access
 switchport access vlan 30
!
interface range FastEthernet0/7-8
 switchport mode access
 switchport access vlan 40

• switchport mode access — sets the port as an access port. Access ports carry traffic for one VLAN only and connect to end devices like PCs.
• switchport access vlan 10 — assigns the port to VLAN 10. Any device connected to this port will be in the Engineering VLAN.

Part C — Configure the trunk link

interface GigabitEthernet0/1
 switchport mode trunk

• The trunk port tags each frame with its VLAN number (802.1Q) before sending it to the router. This allows a single cable to carry traffic for all 4 VLANs.

Part D — Save the configuration

end
write memory

Before configuring the router, let’s see how VLANs isolate traffic. Temporarily assign IPv4 addresses to two PCs in different VLANs to test.

Step 1 — Assign temporary IPs

Go to each PC → Desktop → IP Configuration:

• PC1 (VLAN 10): IPv4 192.168.10.2, Mask 255.255.255.0
• PC2 (VLAN 10): IPv4 192.168.10.3, Mask 255.255.255.0
• PC3 (VLAN 20): IPv4 192.168.20.2, Mask 255.255.255.0

Step 2 — Test within the same VLAN

From PC1, open the Command Prompt and ping PC2:

ping 192.168.10.3

✅ This should succeed — both PCs are in VLAN 10.

Step 3 — Test across VLANs

From PC1 (VLAN 10), ping PC3 (VLAN 20):

ping 192.168.20.2

❌ This should fail! Even though both PCs are connected to the same switch, VLANs keep them completely isolated. Without a router, there is no way for traffic to cross between VLANs.

Now configure the router with sub-interfaces — one per VLAN — using both IPv4 and IPv6 addresses. This is called Router-on-a-Stick because a single physical cable (the trunk) carries all VLAN traffic.

Part A — Hostname, enable IPv6, bring up physical interface

enable
configure terminal
hostname TechNova-R1
!
ipv6 unicast-routing
!
interface GigabitEthernet0/0
 no shutdown

• ipv6 unicast-routing — enables the router to forward IPv6 packets between sub-interfaces. Without this, IPv6 traffic will not be routed.
• no shutdown — activates the physical interface. All sub-interfaces below depend on this being up.

Part B — Create sub-interfaces (IPv4 + IPv6)

interface GigabitEthernet0/0.10
 encapsulation dot1Q 10
 ip address 192.168.10.1 255.255.255.0
 ipv6 address 2001:DB8:CAFE:1::1/64
!
interface GigabitEthernet0/0.20
 encapsulation dot1Q 20
 ip address 192.168.20.1 255.255.255.0
 ipv6 address 2001:DB8:CAFE:2::1/64
!
interface GigabitEthernet0/0.30
 encapsulation dot1Q 30
 ip address 192.168.30.1 255.255.255.0
 ipv6 address 2001:DB8:CAFE:3::1/64
!
interface GigabitEthernet0/0.40
 encapsulation dot1Q 40
 ip address 192.168.40.1 255.255.255.0
 ipv6 address 2001:DB8:CAFE:4::1/64

• encapsulation dot1Q 10 — maps this sub-interface to VLAN 10. Frames tagged with VLAN 10 from the trunk are processed here.
• ip address 192.168.10.1 — the IPv4 default gateway for Engineering PCs.
• ipv6 address 2001:DB8:CAFE:1::1/64 — the IPv6 default gateway for Engineering PCs. Notice the Subnet ID is 1 (matching our plan from Task 1).

Part C — Save the configuration

end
write memory

Go to each PC → Desktop → IP Configuration and assign both IPv4 and IPv6 static addresses.

IPv4 addressing

IPv6 addressing

On the same IP Configuration screen, scroll down to the IPv6 Configuration section. Select Static and enter:

A — IPv4: Ping within the same VLAN

From PC1 (Engineering), ping PC2:

ping 192.168.10.3

✅ This should succeed — both PCs are in VLAN 10.

B — IPv4: Ping across VLANs

Now that the router is configured, test cross-VLAN communication. From PC1 (Engineering), ping PC3 (Sales):

ping 192.168.20.2

✅ This should now succeed! Traffic flows: PC1 → Switch (VLAN 10 tag) → Router (routes to VLAN 20) → Switch (VLAN 20) → PC3.

C — IPv4: More cross-VLAN tests

1. PC1 → PC5: ping 192.168.30.2 (Engineering → Finance)
2. PC3 → PC7: ping 192.168.40.2 (Sales → IT Support)
3. PC8 → PC2: ping 192.168.10.3 (IT Support → Engineering)

D — IPv6: Ping within the same VLAN

From PC1, ping PC2 using IPv6:

ping 2001:DB8:CAFE:1::11

E — IPv6: Ping across VLANs

From PC1 (Engineering), ping PC3 (Sales) using IPv6:

ping 2001:DB8:CAFE:2::10

More IPv6 cross-VLAN tests:

1. PC1 → PC5: ping 2001:DB8:CAFE:3::10 (Engineering → Finance)
2. PC3 → PC7: ping 2001:DB8:CAFE:4::10 (Sales → IT Support)
3. PC8 → PC2: ping 2001:DB8:CAFE:1::11 (IT Support → Engineering)

F — Verification commands on the Router

Run the following commands on the router CLI to verify the configuration:

show ip interface brief
show ipv6 interface brief
show vlans

You should see all 4 sub-interfaces with status up/up and their correct IPv4 and IPv6 addresses.

G — Verification commands on the Switch

Run the following commands on the switch CLI:

show vlan brief
show interfaces trunk

• show vlan brief — confirms which ports are assigned to which VLANs.
• show interfaces trunk — shows the trunk port and which VLANs it carries.

1. What happened when you tried to ping across VLANs before configuring the router (Task 4)? Why?
2. What is the difference between an access port and a trunk port?
3. Why do we use sub-interfaces on the router instead of separate physical interfaces?
4. How many /64 subnets could TechNova create from their /48 prefix? Will they ever run out?
5. If TechNova opens a 5th department (Marketing), what VLAN number and IPv6 subnet would you assign?
6. What are two benefits of using VLANs to segment a network?

In this practical you have:

• Planned IPv6 subnets by dividing a /48 prefix into /64 subnets (one per department)
• Created 4 VLANs on a switch and assigned access ports to each
• Demonstrated VLAN isolation — devices in different VLANs cannot communicate without a router
• Configured a trunk link between the switch and router
• Set up inter-VLAN routing using sub-interfaces (router-on-a-stick)
• Assigned dual-stack (IPv4 + IPv6) addresses to all devices
• Verified connectivity using ping for both IPv4 and IPv6 across all VLANs
• Used verification commands: show vlan brief, show interfaces trunk, show ip interface brief, show ipv6 interface brief