Secondary IP in uOS: Expanding Network Flexibility

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The Secondary IP feature in uOS 1.31 allows administrators to assign multiple IP addresses to a single network interface. This capability is useful for expanding network addressing, managing multiple services, and ensuring better network segmentation—all without requiring additional hardware.

1. What is a Secondary IP?

A Secondary IP is an additional IP address assigned to an existing network interface. This enables a single physical interface to handle multiple subnets or services.

• Expands IP availability without adding new hardware
• Allows multiple subnets on the same interface
• Useful for hosting different services on separate IPs

2. Common Use Cases for Secondary IPs

Scenario 1: Multiple Subnets on One Interface

• Allows two different subnets to exist on the same physical interface
• Example:
  • Primary IP: 192.168.169.1/24
  • Secondary IP: 10.10.10.1/24
• This is commonly used by ISPs, where:DHCP clients connect via the Primary IPStatic IP clients connect via the Secondary IP

Scenario 2: Assigning Specific IPs for Different Services

• Example: Hosting VPN & General Traffic on Separate IPs
  • Primary IP (61.227.75.25) → General internet traffic
  • Secondary IP (61.227.75.26) → Dedicated for VPN connections

This method ensures VPN traffic is routed separately from general Internet usage.

3. How to Configure a Secondary IP in uOS

Web GUI Configuration

• Navigate to: Network → Interface
• Select the interface (e.g., GE4)
• Set the Address Assignment to "Fixed" (Required for Secondary IPs)
• Click “Add Secondary IP”
• Enter the new subnet and IP
• Apply settings

Note:

• Secondary IPs cannot be assigned to DHCP or PPPoE interfaces
• Each IP must belong to a different subnet