This is a small lab network implementing Layer 2 redundancy, Layer 3 segmentation, and integrated IP telephony services. The objective was to design and troubleshoot a multi-VLAN architecture supporting:
- Segmented user and voice networks.
- Centralized DHCP services.
- Inter-VLAN routing on a Layer 3 core.
- EtherChannel uplinks.
- Rapid-PVST spanning tree optimization.
- Cisco Call Manager Express (CME) for VoIP call control. The topology follows a hierarchical design model (Core–Distribution–Access).
Network Topology:
Core Layer:
- Core1 (Layer 3 Switch). Function: Inter-VLAN routing using SVIs, STP Root Bridge (Rapid-PVST), Default gateways for all VLANs, DHCP relay (ip helper-address), EtherChanell with PaGP.
- Destribution 1 and 2. (2 L3 Switches)
- Access (2 Switches, different floors). Providing access to the end devices.
VLAN Design
- VLAN 10: HR, Subnet: 192.168.0.0/23, Default Gateway: 192.168.0.1/23.
- VLAN 20: Management, Subnet: 192.168.2.0/23, Default Gateway: 192.168.2.1/23.
- VLAN 30: Phones, Subnet: 192.168.4.0/23, Default Gateway 192.168.4.1/23.
- VLAN 40: Users, Subnet: 192.168.6.0/23, Default Gateway 192.168.6.1/23.
- VLAN 50: Servers, Subnet: 192.168.8.0/23, Default Gateway 192.168.8.1
- VLAN 99: Native. Inter-VLAN routing is performed entirely on the Core Layer 3 switch using SVIs.
Spanning Tree Design:
- STP Mode: Rapid-PVST.
- Root Bridge: Core1. Core1 was manually configured as root to ensure deterministic forwarding paths, prevent suboptimal blocking, maintain predictable failover behavior.
EtherChannel Implementation:
- Uplinks between Core and Distribution switches are bundled using PAgP.
DHCP:
- DHCP Server Location: Behind Distribution layer (Server VLAN).
- Centralized DHCP model.
- ip helper-address was configured on each SVI on the Core switch.
VoIP: -Voice VLAN: 30 -CME Router IP : 192.168.4.5/23
Troubleshooting Scenarios Resolved:
- Incorrect DHCP Option 150 preventing phone registration. For this one I did not add correct TFTP Server Address on DHCP VLAN 30 (voice) pool. I added the default SVI gateway but I should have added the IP interface of the CME Router.
- Did not add ip-helper address on each SVI causing DHCP to fail.