Day 1 – Multi-Site Enterprise Network Project (CCNA Practice and Interview Preparation)

Today I started building a multi-site enterprise network in Cisco Packet Tracer. This project serves two purposes:

1. It is a large CCNA-level lab to practice routing, switching, VLANs, trunking, OSPF, and WAN design.
2. It will be used as a demonstration project for my upcoming IT Infrastructure Apprenticeship interview.

The network design includes three sites: Headquarters, Office 1, and Office 2. Each site contains a router, a multilayer L3 switch, a Layer 2 access switch, WiFi access points, multiple VLANs, and voice VLAN capability. All Internet traffic is centralised at HQ, with Office 1 and Office 2 routing through the HQ router to reach the Internet.

I created a full addressing plan using a structured system:
HQ uses 10.10.x.x subnets for each VLAN.
Office 1 uses 10.20.x.x subnets.
Office 2 uses 10.30.x.x subnets.

WAN links use standard /30 point-to-point networks: 10.255.1.0/30 between HQ and Office 1, and 10.255.2.0/30 between Office 1 and Office 2.

I also clarified how OSPF works in this environment. Each site advertises its internal VLAN networks into OSPF, and HQ advertises the default route (0.0.0.0). This allows Office 1 and Office 2 to route all unknown traffic to HQ, which performs NAT and forwards it to the Internet. We also covered why the passive-interface command is used, and why static routes are not needed when OSPF is active.

Several important routing concepts were reviewed, including how next-hop addresses work, when static routes are required, and why directly connected networks do not need static routes.

I configured the Headquarters L3 switch today. This included creating all VLANs (Users, Management, Corporate WiFi, Guest WiFi, Voice, and Native VLAN 99), assigning gateway IP addresses (SVIs), configuring trunk uplinks, enabling IP routing, and setting up the OSPF process. I also ensured that only the uplink to the HQ router is an active OSPF interface, while all VLAN interfaces are passive.

A number of real troubleshooting issues came up, including native VLAN mismatches, STP blocking due to inconsistent VLANs, OSPF failing to start because IP routing was not enabled, and Packet Tracer switch model limitations. These were fixed by using the correct switch model, enabling IP routing, and adjusting trunk settings on both ends.

One workflow improvement today was preparing all configurations in Notepad before pasting them into Packet Tracer. This speeds up deployment, reduces errors, and is similar to how configurations are handled in real network engineering.

In summary, today I completed the following:
Planned the topology.
Built the addressing scheme.
Configured all routers.
Configured the HQ L3 switch.
Enabled OSPF at HQ.
Set up trunking and VLAN structure.
Troubleshot VLAN and routing issues.

Next steps for tomorrow are:
Configure the L3 switches for Office 1 and Office 2.
Configure all L2 access switches.
Configure trunk ports for the wireless access points.
Set up DHCP for all VLANs.
Add DNS configuration.
Test routing, VLANs, WiFi, OSPF neighbours, and Internet connectivity.

At the end of this project, I will have a complete, professional multi-site enterprise lab that is suitable for CCNA practice and as strong evidence of networking skills for my apprenticeship interview.