This project simulates a complete multi-AS network architecture involving:

  • an Enterprise Network (Admin, Dev, Marketing)
  • an ISP Backbone (AS5)
  • a Cloud Provider network (AS567)
  • a Personal / Remote network
  • dynamic routing (OSPF + BGP)
  • redundancy (HSRP, dual uplinks)
  • tunnels & NAT
  • multi-tier LAN design (access / distribution / core)

It was built and validated entirely in GNS3.

🖥️ Network Topology

Topology

📘 Network Addressing Summary

Category Element / Link Subnet / IP Notes
Enterprise Network (AS450) Administrators VLAN 192.168.10.0/24 VLAN 10
  Developers VLAN 192.168.20.0/24 VLAN 20
  Marketing VLAN 192.168.30.0/24 VLAN 30
  Maintenance VLAN 192.168.99.0/28 VLAN 99
  Public IP 223.1.2.136/29 Enterprise external range
Operator Backbone (AS5) ROS1 Backbone 12.0.0.0/29 Area 0
  ROS2 Backbone 12.0.10.0/29 Area 0
Personal Network (Area 35) Personal Subnet 192.168.47.0/28 Home LAN
  Gateway 192.168.47.1 Home router
  Public IP 12.1.2.3 User external IP
Cloud Provider (AS567) Intranet Subnet 192.168.60.0/24 via RE2
  Intranet Gateway 192.168.60.1 —
  Intra Web Server 192.168.60.2 —
  Intranet Server 192.168.60.3 —
  Internet Subnet 163.173.19.224/28 via RE3
  Internet Gateway 163.173.19.225 —
  Internet Web Server 163.173.19.226 —
  Internet Intranet Server 163.173.19.227 —
Point-to-Point Links (A–G) Link A 223.1.2.128/31 P2P
  Link B 163.173.18.254/31 P2P
  Link C 163.173.19.222/31 P2P
  Link D 12.1.2.2/31 P2P
  Link E 223.1.2.130/31 P2P
  Link F 172.12.99.0/31 Area 1
  Link G 13.0.0.0/31 Area 10

🎯 Objectives

The main goals of this architecture were:

1. Replace static routing with dynamic routing

  • OSPF Area 0 for the ISP backbone
  • iBGP + eBGP peering between ASes
  • Controlled redistribution (OSPF ↔ BGP)

2. Improve interconnection between all networks

  • Enterprise → ISP
  • ISP → Cloud Provider
  • Personal network → ISP → Cloud

3. Add redundancy & high availability

  • HSRP for gateway failover
  • Dual uplinks towards ISP
  • Core/distribution/access architecture for LAN

4. Secure and optimize internal traffic

  • VLAN segmentation
  • NAT boundaries
  • Private tunnels for intranet and remote access

🧩 Architecture Overview

Enterprise Network (AS450)

  • 3 floors (Admin, Dev, Marketing)
  • VLAN segmentation per department
  • DHCP, NAT, ACLs
  • Three-tier design:
    • Access (ASL1/ASL2/ASL3)
    • Distribution (DSL1/DSL2)
    • Core (CRE1/CRES1)
  • HSRP for gateway redundancy

ISP Network (AS5)

  • OSPF Backbone (Area 0)
  • Six core routers (RO1 → RO6)
  • Dual redundant mesh
  • Route redistribution to BGP
  • Public IP allocation

Cloud Provider (AS567)

  • Public subnet + DMZ
  • Internal services (Web, Intranet)
  • External services (Internet-facing servers)
  • Border routers (RE2/RE3) → eBGP

Personal Network

  • NAT, DHCP, client testing
  • BGP/OSPF learned routes via ISP

🔀 Routing Design

OSPF

  • ISP backbone runs Area 0
  • Fast convergence
  • Stable neighbor adjacency between all RO* routers
  • LSAs reflect link failure in real time

BGP

  • eBGP between:
    • Enterprise ↔ ISP
    • ISP ↔ Cloud Provider
  • iBGP inside Cloud AS
  • Path manipulation for preferred routes
  • Public IP advertisements

Redistribution

  • OSPF ↔ BGP carefully controlled
  • Avoided loops using filtering + metric tuning

🌐 Services & Features

✔ VLANs & Inter-VLAN routing Each department has its own subnet.

✔ HSRP Provides gateway redundancy for LAN clients.

✔ NAT

  • NAT overload for enterprise private addresses
  • Public NAT for Cloud web services

✔ Tunnels Encrypted tunnels used for intranet access and remote work.

✔ DHCP Automatic addressing in enterprise floors.

✔ ACLs Traffic filtering between departments + WAN access.

🛠️ Testing & Validation

The following scenarios were tested:

🔹 link failure → path convergence via OSPF
🔹 BGP peer failure → fallback path
🔹 failover between HSRP primary/standby
🔹 Cloud service reachability tests
🔹 VLAN isolation & inter-VLAN routing
🔹 NAT validation (inside → outside)
🔹 tunnel connectivity checks

All tests were performed using:

  • VPCS clients
  • Debian VMs
  • PING, TRACEROUTE, IPERF
  • GNS3 packet captures

📚 What I Learned

  • Designing real-world multi-AS architectures
  • Understanding redistribution pitfalls
  • Implementing high availability with HSRP
  • Tuning BGP & OSPF for predictable failover
  • VLAN design for multi-floor enterprise networks
  • Cloud/ISP interconnect logic
  • Managing complexity in large topologies

If you want to explore all configurations, scenarios, and diagrams:
👉 Full project root folder