Dual-Stack IPv4 & IPv6 Lab

Why dual stack matters

IPv4 is still everywhere — but the global IPv4 pool is exhausted. Dual stack runs IPv4 and IPv6 on the same interfaces, the same routers, and the same hosts so legacy systems keep working while you build toward IPv6-native designs.

This lab walks through a realistic Packet Tracer 8.2.2 topology: two LANs behind an Edge router, dual-homed to ISP-A (primary) and ISP-B (backup), with a dual-stack Server reachable over both address families. You configure addressing, parallel static routing, failover paths, and observe SLAAC and Router Advertisements (RAs) on LAN B.

Lab files & placeholders

Download the starter topology from the Networking-Courses repo and apply the base config from basic.cfg. Substitute U with your student U number everywhere it appears (e.g. 198.18.U.10 → 198.18.100.10). Rename deliverables to 03-username.pkt and 03-username.txt per your course brief.

Network topology

Reference diagram from the course materials: 03-PT-Topology.png.

Power on every device before you begin — Packet Tracer ships with devices off by default.

Part A — Interface addressing

Addressing plan

Every router needs ipv6 unicast-routing before it will forward IPv6. Assign both families on each interface as shown.

| Device | Interface | IPv4 | GUA IPv6 | Link-local | Role | |--------|-----------|------|----------|------------|------| | Edge | G0/0 | 198.18.U.1/25 | 2010:acad:U:a::1/64 | fe80::1 | LAN A gateway | | Edge | G0/1 | 198.18.U.129/25 | 2010:acad:U:b::129/64 | fe80::1 | LAN B gateway | | Edge | S0/0/0 | 203.0.113.253/30 | 2001:fab:203:a::253/64 | fe80::1 | To ISP-A | | Edge | S0/0/1 | 203.0.113.249/30 | 2001:fab:203:b::249/64 | fe80::1 | To ISP-B | | ISP-A | S0/0/0 | 203.0.113.254/30 | 2001:fab:203:a::254/64 | fe80::a | To Edge | | ISP-A | G0/0 | 192.0.2.254/24 | 2001:db8:192::254/64 | fe80::a | Server network | | ISP-B | S0/0/1 | 203.0.113.250/30 | 2001:fab:203:b::250/64 | fe80::b | To Edge | | ISP-B | G0/0 | 192.0.2.253/24 | 2001:db8:192::253/64 | fe80::b | Server network | | Server | NIC | 192.0.2.69/24 | 2001:db8:192::69/64 | fe80::69 | Dual-stack target | | PC-A | NIC | 198.18.U.10/25 | 2010:acad:U:a::10/64 | fe80::10 | Static both families | | PC-B | NIC | 198.18.U.130/25 | SLAAC | SLAAC | Auto IPv6 on LAN B |

Link-local uniqueness

Link-local addresses (LLAs) must be unique per interface on a link — not globally unique. Two routers can both use fe80::1 on different interfaces, but never two devices on the same segment with the same LLA.

Example Edge configuration

Edge — dual-stack interfaces (sample)

ipv6 unicast-routing ! interface GigabitEthernet0/0 description LAN A ip address 198.18.U.1 255.255.255.128 ipv6 address 2010:acad:U:a::1/64 ipv6 address FE80::1 link-local no shutdown ! interface GigabitEthernet0/1 description LAN B ip address 198.18.U.129 255.255.255.128 ipv6 address 2010:acad:U:b::129/64 ipv6 address FE80::1 link-local no shutdown

CO1 — Verify interface state

Open the router console so command output wraps cleanly — truncated columns hide misconfigured addresses.

On every router:

CO1 — interface verification (routers)

show ip int brief | ex una show ipv6 int brief

Packet Tracer quirk

show ipv6 int brief does not support the | ex una filter in Packet Tracer. Run it without a pipe.

On Edge — inspect multicast groups on LAN A:

CO1 — Edge G0/0 detail

show ipv6 interface gi0/0

When you review LLA and GUA, expect Joined group addresses such as:

Typical joined groups

Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1

| Multicast | Meaning | |-----------|---------| | FF02::1 | All nodes on this link | | FF02::2 | All routers on this link | | FF02::1:FFxx:xxxx | Solicited-node — used by NDP to resolve neighbors |

IPv6 replaces broadcast with scoped multicast — efficient on shared segments.

On PC-A and PC-B:

CO1 — host addressing

ipconfig /all

SLAAC and EUI-64 on PC-B

PC-B uses SLAAC on LAN B. With U=100, output resembles:

PC-B SLAAC example (U=100)

Physical Address................: 0060.5C90.3CBD Link-local IPv6 Address.........: FE80::260:5CFF:FE90:3CBD IPv6 Address....................: 2010:ACAD:100:B:260:5CFF:FE90:3CBD

EUI-64 interface ID generation:

Split the 48-bit MAC in half
Insert FFFE in the middle
Flip the 7th bit (Universal/Local) of the first octet
Append the 64-bit interface ID to the /64 prefix from the RA

The host gets a unique address without DHCPv6 — prefix comes from the router advertisement.

Part B — Routing configuration

LAN hosts reach the Internet through the Edge router. ISP-A is the primary path; ISP-B is backup using floating static routes (higher administrative distance). Both ISPs need return routes toward the internal LANs behind Edge.

Static routing in Packet Tracer

Packet Tracer does not support fully specified static routes. Use directly connected routes (exit interface) or next-hop routes (GUA next-hop). For IPv6, link-local next-hops normally require exit interface too — so this lab uses GUA next-hops throughout for IPv6 compatibility in PT.

Edge — default routes (IPv4 + IPv6)

| Route | Type | Path | AD | |-------|------|------|-----| | Primary default | Directly connected | ISP-A (S0/0/0) | 1 (connected) | | Floating default | Directly connected | ISP-B (S0/0/1) | U (your U number) |

Mirror the same logic for IPv6 defaults using the parallel IPv6 next-hops on each serial link.

Edge — IPv4 default routes (pattern)

ip route 0.0.0.0 0.0.0.0 Serial0/0/0 ip route 0.0.0.0 0.0.0.0 Serial0/0/1 U

Replace U in the floating route AD with your student number (e.g. 100).

ISP-A — routes to LAN A and LAN B

Configure next-hop or recursive static routes to both LANs via Edge. Add floating backups via ISP-B with AD U.

ISP-B — routes to LAN A and LAN B

Mirror ISP-A: primary routes via Edge, floating backups via ISP-A with AD U.

CO2 — Routing tables

On every router:

CO2 — static routing evidence

show ip route static show ipv6 route

IPv6 static filter

Packet Tracer's show ipv6 route does not support a static keyword filter — capture the full table and highlight static entries (S code) in your submission notes.

Confirm primary and floating routes appear with the expected AD values before moving to connectivity tests.

Part C — Path verification

When routing is correct, PC-A and PC-B reach the Server on both address families. Failover should work when a primary WAN link goes down.

CO3 — baseline traceroute

PC-B> tracert 192.0.2.69
PC-A> tracert 2001:db8:192::69

Failover test — ISP-A link down

CO3 — primary path failure

ISP-A(config)# interface s0/0/0
ISP-A(config-if)# shutdown
ISP-A# show ip route static
ISP-A# show ipv6 route
Edge# show ip route static
Edge# show ipv6 route static
PC-B> tracert 192.0.2.69
PC-A> tracert 2001:db8:192::69

Floating routes should appear in the routing table and traceroute should shift to the backup path.

Failover test — ISP-B link down

Restore ISP-A, then shut ISP-B's WAN toward Edge and repeat show commands. From ISP-B, traceroute to both PC-A addresses confirms return-path reachability when the link returns.

CO3 — backup path failure

ISP-A(config-if)# no shutdown
ISP-B(config)# interface s0/0/1
ISP-B(config-if)# shutdown
ISP-B# show ip route static
ISP-B# show ipv6 route
ISP-B# tracert 198.18.U.10
ISP-B# tracert 2010:acad:U:a::10

Bring all interfaces back up before Part D.

Part D — NDP and Router Advertisements

SLAAC depends on ICMPv6 Router Advertisements. When a host joins LAN B, it listens for RAs from Edge containing the /64 prefix and default-router information.

Isolate LAN B for clean debug output:

Part D — RA observation setup

Edge(config)# interface s0/0/0
Edge(config-if)# shutdown
Edge(config)# interface s0/0/1
Edge(config-if)# shutdown
Edge(config)# interface g0/0
Edge(config-if)# shutdown
Edge# debug ipv6 nd

Connect PC-NEW to LAN B with IPv6 set to Automatic. You should see lines like:

Sample debug ipv6 nd output

ICMPv6-ND: (GigabitEthernet0/1, FE80::1) send RA to FF02::1
ICMPv6-ND: (GigabitEthernet0/1, FE80::1) Sending RA(1800) to FF02::1
ICMPv6-ND: MTU = 1500
ICMPv6-ND: prefix = 2010:acad:U:b::/64

Part D — cleanup

Edge# no debug all

Capture ipconfig /all from PC-NEW showing the auto-generated LLA and GUA, then re-enable all Edge interfaces.

These messages show how hosts learn prefixes without DHCPv6 — NDP replaces ARP and broadcast discovery in IPv6.

Submission deliverables

| File | Contents | |------|----------| | 03-username.txt | CO1–CO3 command output, RA debug lines, PC ipconfig /all | | 03-username.pkt | Completed Packet Tracer topology |

Organize your text file with clear section headers matching CO1, CO2, and CO3 so markers can find evidence quickly.

Key takeaways

| Concept | Dual-stack lesson | |---------|-------------------| | Parallel stacks | Same topology, two independent routing tables — configure both deliberately | | GUA vs LLA | Global unicast for routing; link-local for on-link NDP and next-hop | | Floating statics | Higher AD backup routes — test by shutting primary links | | SLAAC + RA | Host builds address from prefix + interface ID; debug with debug ipv6 nd | | PT limits | No fully specified IPv6 statics — use GUA next-hops |

Related material

IPv6 Implementation topic guide — address types, SLAAC, OSPFv3
Static & floating routes lesson — AD and backup path design
Original lab — Networking-Courses