Advanced Networking Topology Lab

Advanced GNS3 networking lab that models an IPv4/IPv6 service-provider core and a customer MPLS L3VPN. The topology combines multi-area OSPF, iBGP/eBGP, a route reflector, MPLS/LDP, VPNv4, a VRF, and QoS.

Lab status: the repository includes corrected startup configurations and static validation artifacts. Start the topology in GNS3 and run the verification commands below to confirm live adjacencies and end-to-end forwarding in your environment.

Topology

The GNS3 project contains 10 nodes and 9 links:

PC1 — CE-HQ — R1 — R2 — CE-BR — PC2
                 |     |
                 R3 — R4
                 |     |
             ASBR-2122 ASBR-2123

Device	Role
R1, R2, R3, R4	Provider routers in AS 2121. R1 and R2 are PEs; R3 and R4 are core/P routers and external BGP edge points.
R3	iBGP and VPNv4 route reflector for the provider routers.
ASBR-2122	External peer in AS 2122, connected to R3; this is the preferred external path.
ASBR-2123	External peer in AS 2123, connected to R4; this is the backup external path.
CE-HQ, CE-BR	Customer-edge routers for the headquarters and branch sites.
PC1, PC2	VPCS hosts on the HQ and branch LANs.

Routing and service design

Provider underlay

The AS 2121 core uses OSPFv2 and OSPFv3 with this area design:

Link or component	OSPF area	Purpose
R3 — R4	0	Backbone/core transit link.
R1 — R3	1	Standard transit area.
R1 — R2	2 (stub)	Stub area serving R2.
R1 ↔ R3 virtual link	Through area 1	Connects R1 logically to the backbone because it has no physical area-0 interface.

MPLS/LDP is enabled only on the provider-core links: R1-R3, R1-R2, and R3-R4. It is deliberately excluded from PE-CE and external AS links.

BGP and path preference

• iBGP: provider loopbacks peer through R3, which acts as the route reflector.
• VPNv4: R1 and R2 exchange customer-VRF routes through R3; extended communities are sent for route-target handling.
• eBGP: R3 peers with AS 2122 and R4 peers with AS 2123 for IPv4 and IPv6.
• Preferred exit: routes received from AS 2122 are assigned local preference 200, making the R3 → ASBR-2122 path preferred over the default preference of 100.
• Backup inbound path: advertisements sent toward AS 2123 are prepended with AS 2121 three times, making that path less attractive to external networks.

Customer VPN

The customer service is carried in the ENTERPRISE VRF:

• R1 ↔ CE-HQ: eBGP between AS 2121 and customer AS 65010.
• R2 ↔ CE-BR: RIP version 2 inside the ENTERPRISE VRF.
• R1 and R2: MP-iBGP VPNv4 via the R3 route reflector.
• R1: QoS marks traffic entering from the HQ CE and applies a priority/fair-queue policy on the R1-to-R3 core link.

Addressing plan

Customer VPN IPv4 addressing

Segment	Network	Assigned addresses
HQ LAN	192.168.10.0/24	CE-HQ: 192.168.10.1, PC1: 192.168.10.10
HQ PE-CE link	192.168.100.0/30	R1: 192.168.100.1, CE-HQ: 192.168.100.2
Branch PE-CE link	192.168.200.0/30	R2: 192.168.200.1, CE-BR: 192.168.200.2
Branch LAN	192.168.20.0/24	CE-BR: 192.168.20.1, PC2: 192.168.20.10

Provider and external addressing

Link	IPv4 network	IPv6 network
R1 — R3	121.1.0.0/30	2123:4561:0:1::/64
R1 — R2	121.1.0.4/30	2123:4561:0:2::/64
R3 — R4	121.1.0.8/30	2123:4561:0:3::/64
R3 — ASBR-2122	121.1.0.12/30	2123:4561:0:4::/64
R4 — ASBR-2123	121.1.0.16/30	2123:4561:0:5::/64

Provider loopbacks use 121.0.0.1/32 through 121.0.0.4/32 and 2123:4561:0:F::1/128 through ::4/128. The external AS loopbacks are 122.0.0.1/32 / 2123:4562:0:F::1/128 and 123.0.0.1/32 / 2123:4563:0:F::1/128.

Evidence

The evidences/ folder contains screenshots recorded during lab work. They document individual reachability and routing observations; they should be interpreted together with fresh live validation after the topology is started.

Core and customer-path evidence

CE-HQ to CE-BR traceroute

This capture shows a traceroute from CE-HQ to CE-BR using the provider path R1 → R3 → R2. It demonstrates CE-to-CE reachability at the time it was captured. It does not by itself prove PC1 to PC2 connectivity; use the VPCS checks below after startup.

R1 to R4 reachability

This capture records successful R1-to-R4 reachability across the provider core.

External BGP and IPv6 evidence

R1 view of AS 2122

R1 IPv6 view of AS 2122

R1 view of AS 2123

These screenshots provide historical BGP/IPv6 observations for the external AS paths. Because BGP state and best paths are dynamic, confirm the current neighbor state and selected routes with the commands in the next section.

Running the lab

1. Open project/project.gns3 in GNS3.
2. Configure a Cisco 7200-compatible IOS image that supports OSPFv3, BGP with VPNv4, MPLS/LDP, VRF, and QoS. Cisco IOS images are not distributed in this repository.
3. Confirm that all router and VPCS nodes are started. The startup configurations are under project/project-files/; exported copies are in configs/.
4. Wait for OSPF, LDP, and BGP convergence before testing reachability.

Verification checklist

Run the following commands on the relevant routers after startup:

show ip ospf neighbor
show ip ospf virtual-links
show ipv6 ospf neighbor
show mpls ldp neighbor
show mpls forwarding-table
show ip bgp summary
show bgp ipv6 unicast summary
show bgp vpnv4 unicast all summary
show ip route vrf ENTERPRISE
show bgp vpnv4 unicast vrf ENTERPRISE

Expected outcomes:

• OSPF adjacencies are established on the core links, and the R1-R3 virtual link is up.
• LDP neighbors appear only on the three AS 2121 core links.
• IPv4 and IPv6 eBGP sessions are established with both external ASBRs.
• R1 and R2 have routes to the opposite customer LAN in VRF ENTERPRISE.
• AS 2122-learned routes are preferred while available.

On the VPCS endpoints, validate the complete customer path:

# On PC1
show ip
ping 192.168.20.10
trace 192.168.20.10

# On PC2
show ip
ping 192.168.10.10
trace 192.168.10.10

Repository layout

Path	Contents
asset/	Topology diagram used in this README.
evidences/	Historical screenshots of traceroute, ping, BGP, and IPv6 observations.
configs/	Exported Cisco IOS device configurations.
project/	GNS3 project file, device startup configurations, VPCS startup files, and a detailed Portuguese implementation guide.
.gitignore	Excludes local tool settings, runtime files, and the portable archive containing an IOS image.

Notes on publishing

The ignored advanced-network.gns3project portable archive embeds a Cisco IOS image. Do not publish or redistribute it unless you have confirmed the relevant licensing rights. Local .claude/ settings are also ignored to avoid committing environment-specific configuration or credentials.