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PTL-0054 Routing

Dual-Stack IPv4 and IPv6 Branch Network

Design, deploy, and verify dual-stack IPv4 and IPv6 enterprise branch connectivity using static and default routing across a hub-and-spoke transit topology. Configure simultaneous IPv4 and IPv6 addressing, establish dual-stack default gateways, and isolate routing misconfigurations in Cisco IOS environments.

Level
Advanced
Time
75 min
Packet Tracer
8.2+
Simulator
Tested in Packet Tracer
You configure
Branch-1-R1, Branch-2-R3, HQ-R2, SW-BR1, SW-BR2
Last reviewed
On this page

FILES Packet Tracer topology

Download starter file

starter.pkt, 103 KB. Open it in Cisco Packet Tracer 8.2+. Install Packet Tracer.

Solution / reference file

The completed topology with every task configured. Try the lab first and use this to check your work or when you are stuck.

Download solution file

completed.pkt, 103 KB.

File checksums (SHA-256)
starter.pkt
98207f874f9ea8b2fe7a5271e8683cfea98e8897f95f8dc3ada766977853703c
completed.pkt
9b8859f43f5fe39a1095bbc0cd7f2c3fbf69dc14a459e201a57f6015f6f25ed3

Part of BSIT Networking Curriculum Learning Path (step 33 of 56) and CCNA-Aligned Topical Study Path (step 33 of 56).

Learning Objectives#

  • Configure dual-stack IPv4 and IPv6 interface addressing and link-local scopes on branch and core routers.
  • Implement simultaneous IPv4 and IPv6 static and default routes across point-to-point transit networks.
  • Verify end-to-end bidirectional dual-stack reachability between remote branch LAN subnets.
  • Diagnose and resolve routing anomalies including invalid next-hop IP addresses and missing IPv6 default routes.
  • Validate routing tables, neighbor discovery tables, and ARP tables for deterministic dual-stack forwarding.

Prerequisites#

Topology#

Dual-Stack IPv4 and IPv6 Branch Network Topology Diagram
Dual-Stack IPv4 and IPv6 Branch Network Topology Diagram
[ PC-BR1 ] (192.168.10.10 / 2001:db8:acad:10::10)
    | Fa0
    | Fa0/10
[ SW-BR1 ] (Catalyst 2960)
    | Gi0/1
    | Gi0/0
[ Branch-1-R1 ] (Cisco 2911)
    | Gi0/1 (WAN 1: 10.1.12.1/30 / 2001:db8:acad:12::1/64)
    |
    | Gi0/1
[ HQ-R2 ] (Cisco 2911) [Loopback0: 172.16.1.1/24 / 2001:db8:acad:100::1/64]
    | Gi0/2
    |
    | Gi0/2 (WAN 2: 10.1.23.3/30 / 2001:db8:acad:23::3/64)
[ Branch-2-R3 ] (Cisco 2911)
    | Gi0/0
    | Gi0/1
[ SW-BR2 ] (Catalyst 2960)
    | Fa0/10
    | Fa0
[ PC-BR2 ] (192.168.20.10 / 2001:db8:acad:20::10)

Addressing Table#

Device Name Interface IPv4 Address / Prefix IPv6 Address / Prefix Default Gateway (IPv4 / IPv6) Purpose / Connection
Branch-1-R1 Gi0/0 192.168.10.1 /24 2001:db8:acad:10::1 /64 N/A LAN Gateway (Branch 1)
Branch-1-R1 Gi0/1 10.1.12.1 /30 2001:db8:acad:12::1 /64 N/A WAN Transit to HQ-R2 Gi0/1
HQ-R2 Gi0/1 10.1.12.2 /30 2001:db8:acad:12::2 /64 N/A WAN Transit to Branch-1-R1 Gi0/1
HQ-R2 Gi0/2 10.1.23.1 /30 2001:db8:acad:23::2 /64 N/A WAN Transit to Branch-2-R3 Gi0/2
HQ-R2 Loopback0 172.16.1.1 /24 2001:db8:acad:100::1 /64 N/A Central Services / Management
Branch-2-R3 Gi0/2 10.1.23.2 /30 2001:db8:acad:23::3 /64 N/A WAN Transit to HQ-R2 Gi0/2
Branch-2-R3 Gi0/0 192.168.20.1 /24 2001:db8:acad:20::1 /64 N/A LAN Gateway (Branch 2)
PC-BR1 FastEthernet0 192.168.10.10 /24 2001:db8:acad:10::10 /64 192.168.10.1 / 2001:db8:acad:10::1 Branch 1 Client Host
PC-BR2 FastEthernet0 192.168.20.10 /24 2001:db8:acad:20::10 /64 192.168.20.1 / 2001:db8:acad:20::1 Branch 2 Client Host

Lab Tasks#

  1. Enable ipv6 unicast-routing globally on all Cisco routers (Branch-1-R1, HQ-R2, Branch-2-R3).
  2. Configure dual-stack IPv4 and IPv6 addresses on all router physical and loopback interfaces.
  3. Configure dual-stack static default routes on spoke branch routers (Branch-1-R1 and Branch-2-R3) pointing to HQ-R2.
  4. Configure explicit static IPv4 and IPv6 routes on core router HQ-R2 to reach both branch LAN subnets.
  5. Configure static dual-stack addressing on end devices (PC-BR1 and PC-BR2).
  6. Identify and resolve intentional routing faults present in the starter network.

Configuration Walkthrough#

Step 1: Configure Branch-1 Router (Branch-1-R1)#

Enable dual-stack routing and configure LAN and WAN interfaces:

Branch-1-R1# configure terminal
Branch-1-R1(config)# hostname Branch-1-R1
Branch-1-R1(config)# ipv6 unicast-routing
Branch-1-R1(config)# no ip domain-lookup

Branch-1-R1(config)# interface GigabitEthernet0/0
Branch-1-R1(config-if)# description Branch 1 LAN Gateway
Branch-1-R1(config-if)# ip address 192.168.10.1 255.255.255.0
Branch-1-R1(config-if)# ipv6 address 2001:db8:acad:10::1/64
Branch-1-R1(config-if)# ipv6 address fe80::1 link-local
Branch-1-R1(config-if)# no shutdown
Branch-1-R1(config-if)# exit

Branch-1-R1(config)# interface GigabitEthernet0/1
Branch-1-R1(config-if)# description WAN to HQ-R2
Branch-1-R1(config-if)# ip address 10.1.12.1 255.255.255.252
Branch-1-R1(config-if)# ipv6 address 2001:db8:acad:12::1/64
Branch-1-R1(config-if)# ipv6 address fe80::1 link-local
Branch-1-R1(config-if)# no shutdown
Branch-1-R1(config-if)# exit

Branch-1-R1(config)# ip route 0.0.0.0 0.0.0.0 10.1.12.2
Branch-1-R1(config)# ipv6 route ::/0 2001:db8:acad:12::2
Branch-1-R1(config)# end
Branch-1-R1# copy running-config startup-config

Step 2: Configure Central Hub Router (HQ-R2)#

Configure core WAN links, loopback service interface, and static routes to both branches:

HQ-R2# configure terminal
HQ-R2# hostname HQ-R2
HQ-R2(config)# ipv6 unicast-routing
HQ-R2(config)# no ip domain-lookup

HQ-R2(config)# interface Loopback0
HQ-R2(config-if)# description Central Services Loopback
HQ-R2(config-if)# ip address 172.16.1.1 255.255.255.0
HQ-R2(config-if)# ipv6 address 2001:db8:acad:100::1/64
HQ-R2(config-if)# exit

HQ-R2(config)# interface GigabitEthernet0/1
HQ-R2(config-if)# description WAN to Branch-1-R1
HQ-R2(config-if)# ip address 10.1.12.2 255.255.255.252
HQ-R2(config-if)# ipv6 address 2001:db8:acad:12::2/64
HQ-R2(config-if)# ipv6 address fe80::2 link-local
HQ-R2(config-if)# no shutdown
HQ-R2(config-if)# exit

HQ-R2(config)# interface GigabitEthernet0/2
HQ-R2(config-if)# description WAN to Branch-2-R3
HQ-R2(config-if)# ip address 10.1.23.1 255.255.255.252
HQ-R2(config-if)# ipv6 address 2001:db8:acad:23::2/64
HQ-R2(config-if)# ipv6 address fe80::2 link-local
HQ-R2(config-if)# no shutdown
HQ-R2(config-if)# exit

HQ-R2(config)# ip route 192.168.10.0 255.255.255.0 10.1.12.1
HQ-R2(config)# ip route 192.168.20.0 255.255.255.0 10.1.23.2
HQ-R2(config)# ipv6 route 2001:db8:acad:10::/64 2001:db8:acad:12::1
HQ-R2(config)# ipv6 route 2001:db8:acad:20::/64 2001:db8:acad:23::3
HQ-R2(config)# end
HQ-R2# copy running-config startup-config

Step 3: Configure Branch-2 Router (Branch-2-R3)#

Enable dual-stack routing and configure interfaces and default routes:

Branch-2-R3# configure terminal
Branch-2-R3(config)# hostname Branch-2-R3
Branch-2-R3(config)# ipv6 unicast-routing
Branch-2-R3(config)# no ip domain-lookup

Branch-2-R3(config)# interface GigabitEthernet0/0
Branch-2-R3(config-if)# description Branch 2 LAN Gateway
Branch-2-R3(config-if)# ip address 192.168.20.1 255.255.255.0
Branch-2-R3(config-if)# ipv6 address 2001:db8:acad:20::1/64
Branch-2-R3(config-if)# ipv6 address fe80::3 link-local
Branch-2-R3(config-if)# no shutdown
Branch-2-R3(config-if)# exit

Branch-2-R3(config)# interface GigabitEthernet0/2
Branch-2-R3(config-if)# description WAN to HQ-R2
Branch-2-R3(config-if)# ip address 10.1.23.2 255.255.255.252
Branch-2-R3(config-if)# ipv6 address 2001:db8:acad:23::3/64
Branch-2-R3(config-if)# ipv6 address fe80::3 link-local
Branch-2-R3(config-if)# no shutdown
Branch-2-R3(config-if)# exit

Branch-2-R3(config)# ip route 0.0.0.0 0.0.0.0 10.1.23.1
Branch-2-R3(config)# ipv6 route ::/0 2001:db8:acad:23::2
Branch-2-R3(config)# end
Branch-2-R3# copy running-config startup-config

Verification#

Verification Matrix#

Check ID Device / Source Target / Destination Protocol Expected Result
POS-01 PC-BR1 PC-BR2 (192.168.20.10) IPv4 ICMP 4/4 replies (0% packet loss)
POS-02 PC-BR1 PC-BR2 (2001:db8:acad:20::10) IPv6 ICMP 4/4 replies (0% packet loss)
POS-03 PC-BR2 HQ-R2 Loopback0 (172.16.1.1) IPv4 ICMP 4/4 replies (0% packet loss)
POS-04 PC-BR2 HQ-R2 Loopback0 (2001:db8:acad:100::1) IPv6 ICMP 4/4 replies (0% packet loss)
POS-05 All Routers Routing Engines System ipv6 unicast-routing active on all 3 routers

IOS Command Verification#

Execute the following commands on each router to inspect dual-stack routing:

Branch-1-R1# show ip route static
Branch-1-R1# show ipv6 route static
Branch-1-R1# show ip interface brief
Branch-1-R1# show ipv6 interface brief

On PC-BR1, verify dual-stack address assignment:

C:\> ipconfig
C:\> ping 192.168.20.10
C:\> ping 2001:db8:acad:20::10

Troubleshooting#

  1. IPv6 Ping Fails with "Request timed out":

    • Verify that ipv6 unicast-routing is enabled on all routers. Without this command, Cisco IOS routers drop IPv6 transit packets.
    • Verify that Branch-2-R3 has a default route ipv6 route ::/0 2001:db8:acad:23::2.
    • Inspect show ipv6 route on HQ-R2 to confirm return routes exist for both branch prefixes.

  2. IPv4 Ping Fails with Destination Host Unreachable:

    • Inspect show ip route on Branch-1-R1. If the default route points to an unreachable next-hop IP (e.g. 10.1.12.5), traffic will be dropped.
    • Update the default route to point to the correct next hop 10.1.12.2: 
      Branch-1-R1(config)# no ip route 0.0.0.0 0.0.0.0 10.1.12.5
Branch-1-R1(config)# ip route 0.0.0.0 0.0.0.0 10.1.12.2

Key Takeaways#

  • Dual-stack operation allows IPv4 and IPv6 to operate concurrently over identical physical infrastructure without mutual interference.
  • Every dual-stack router requires global unicast addresses and automatic or configured link-local addresses (FE80::/10) on all active interfaces.
  • Cisco IOS requires ipv6 unicast-routing to be explicitly configured; IPv6 routing is disabled by default on Cisco routers.
  • Hub-and-spoke transit networks achieve symmetric reachability when spokes deploy default routes and the core hub router maintains explicit static routes to each branch prefix.

References#

Files and Validation Status#

  • assets/starter.pkt: Initial topology with deliberate next-hop routing faults.
  • assets/completed.pkt: Validated dual-stack network with full IPv4 and IPv6 reachability.
  • assets/topology.png: Visual layout of the dual-stack multi-branch network.
  • assets/test_evidence.json: Verification test logs demonstrating 100% test pass rate.
  • configs/Branch-1-R1.txt: Baseline running configuration for Branch 1 router.
  • configs/HQ-R2.txt: Baseline running configuration for HQ central router.
  • configs/Branch-2-R3.txt: Baseline running configuration for Branch 2 router.

Reference configurations

Final device configurations from the solution. Like the solution file, these give the answers away.

Branch-1-R1 Branch-1-R1.txt, 1.1 KB 
Building configuration...

Current configuration : 1040 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Branch-1-R1
!
!
!
!
!
!
!
!
ip cef
ipv6 unicast-routing
!
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX15241HJR-
!
!
!
!
!
!
!
!
!
!
!
no ip domain-lookup
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 description Branch 1 LAN Gateway
 ip address 192.168.10.1 255.255.255.0
 duplex auto
 speed auto
 ipv6 address FE80::1 link-local
 ipv6 address 2001:DB8:ACAD:10::1/64
!
interface GigabitEthernet0/1
 description WAN to HQ-R2
 ip address 10.1.12.1 255.255.255.252
 duplex auto
 speed auto
 ipv6 address FE80::1 link-local
 ipv6 address 2001:DB8:ACAD:12::1/64
!
interface GigabitEthernet0/2
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 10.1.12.2 
!
ip flow-export version 9
!
ipv6 route ::/0 2001:DB8:ACAD:12::2
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Download Branch-1-R1.txt

Branch-2-R3 Branch-2-R3.txt, 1.1 KB 
Building configuration...

Current configuration : 1040 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname Branch-2-R3
!
!
!
!
!
!
!
!
ip cef
ipv6 unicast-routing
!
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX1524OY84-
!
!
!
!
!
!
!
!
!
!
!
no ip domain-lookup
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface GigabitEthernet0/0
 description Branch 2 LAN Gateway
 ip address 192.168.20.1 255.255.255.0
 duplex auto
 speed auto
 ipv6 address FE80::3 link-local
 ipv6 address 2001:DB8:ACAD:20::1/64
!
interface GigabitEthernet0/1
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface GigabitEthernet0/2
 description WAN to HQ-R2
 ip address 10.1.23.2 255.255.255.252
 duplex auto
 speed auto
 ipv6 address FE80::3 link-local
 ipv6 address 2001:DB8:ACAD:23::3/64
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 10.1.23.1 
!
ip flow-export version 9
!
ipv6 route ::/0 2001:DB8:ACAD:23::2
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Download Branch-2-R3.txt

HQ-R2 HQ-R2.txt, 1.3 KB 
Building configuration...

Current configuration : 1301 bytes
!
version 15.1
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname HQ-R2
!
!
!
!
!
!
!
!
ip cef
ipv6 unicast-routing
!
no ipv6 cef
!
!
!
!
license udi pid CISCO2911/K9 sn FTX15245T96-
!
!
!
!
!
!
!
!
!
!
!
no ip domain-lookup
!
!
spanning-tree mode pvst
!
!
!
!
!
!
interface Loopback0
 description Central Services Loopback
 ip address 172.16.1.1 255.255.255.0
 ipv6 address 2001:DB8:ACAD:100::1/64
!
interface GigabitEthernet0/0
 no ip address
 duplex auto
 speed auto
 shutdown
!
interface GigabitEthernet0/1
 description WAN to Branch-1-R1
 ip address 10.1.12.2 255.255.255.252
 duplex auto
 speed auto
 ipv6 address FE80::2 link-local
 ipv6 address 2001:DB8:ACAD:12::2/64
!
interface GigabitEthernet0/2
 description WAN to Branch-2-R3
 ip address 10.1.23.1 255.255.255.252
 duplex auto
 speed auto
 ipv6 address FE80::2 link-local
 ipv6 address 2001:DB8:ACAD:23::2/64
!
interface Vlan1
 no ip address
 shutdown
!
ip classless
ip route 192.168.10.0 255.255.255.0 10.1.12.1 
ip route 192.168.20.0 255.255.255.0 10.1.23.2 
!
ip flow-export version 9
!
ipv6 route 2001:DB8:ACAD:10::/64 2001:DB8:ACAD:12::1
ipv6 route 2001:DB8:ACAD:20::/64 2001:DB8:ACAD:23::3
!
!
!
!
!
!
line con 0
!
line aux 0
!
line vty 0 4
 login
!
!
!
end

Download HQ-R2.txt

SW-BR1 SW-BR1.txt, 1.1 KB 
Building configuration...

Current configuration : 1104 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname SW-BR1
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
 spanning-tree portfast
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
!
end

Download SW-BR1.txt

SW-BR2 SW-BR2.txt, 1.1 KB 
Building configuration...

Current configuration : 1104 bytes
!
version 12.2
no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
!
hostname SW-BR2
!
!
!
!
!
!
spanning-tree mode pvst
spanning-tree extend system-id
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
 spanning-tree portfast
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface FastEthernet0/16
!
interface FastEthernet0/17
!
interface FastEthernet0/18
!
interface FastEthernet0/19
!
interface FastEthernet0/20
!
interface FastEthernet0/21
!
interface FastEthernet0/22
!
interface FastEthernet0/23
!
interface FastEthernet0/24
!
interface GigabitEthernet0/1
!
interface GigabitEthernet0/2
!
interface Vlan1
 no ip address
 shutdown
!
!
!
!
line con 0
!
line vty 0 4
 login
line vty 5 15
 login
!
!
!
!
end

Download SW-BR2.txt

Verification guide

Device models, cabling, expected show output and negative tests for this lab: Verification Guide: PTL-0054 — Dual-Stack IPv4 and IPv6 Branch Network.

  • Routing
  • Dual Stack
  • IPv6 Routing
  • Static Routing
  • Branch Network
  • Cisco IOS
  • Cisco Packet Tracer

This page is generated from labs/routing/dual-stack-ipv4-and-ipv6-branch-network/README.md in the repository. Corrections go there.

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