How to Use Additional IPv4 Addresses on a Dedicated Server

Overview

On our network, only one MAC address is authorized per physical network port. This means that all traffic must originate from the server’s main network interface.

To prevent IP conflicts, MAC spoofing, and network disruptions, additional IPv4 addresses must be configured using routing via the main server IP, not directly on the switch.

This ensures that the server itself handles the traffic forwarding.

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Network Policy

• ✅ Only one MAC address is allowed per physical port

• ❌ No additional MAC addresses (VPS, VM, containers) are permitted on the switch

• ✅ All extra IPv4 addresses must be routed through the main server IP

• ✅ The dedicated server acts as a gateway for its additional IPs

This design improves network stability and security.

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Example Scenario

Main server IP:

10.10.10.55

Additional IPv4 addresses:

10.10.10.56
10.10.10.57

Default gateway of the network:

10.10.10.1

⚠️ Important

Do NOT use 10.10.10.1 as the gateway for additional IPs.

Instead, use the main server IP as the gateway.

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Correct Configuration

Additional IP Configuration

Each additional IP must use the main server IP as its gateway.

Example:

IP Address:   10.10.10.56/XX
Gateway:      10.10.10.55

IP Address:   10.10.10.57/XX
Gateway:      10.10.10.55

Where:

• XX = subnet mask (provided by us)

• 10.10.10.55 = main server IP

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Why This Is Required

Because only one MAC address is allowed:

• The switch only sees the main server

• All traffic must pass through the server

• The server routes packets internally

This prevents:

• MAC spoofing

• Unauthorized IP usage

• Network instability

• Service interruptions

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Server Role

Your dedicated server acts as:

• A router

• A gateway

• A traffic forwarder

All additional IP traffic goes through the main interface.

This applies to:

• Virtual machines

• Containers

• VPS

• Custom network setups

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Typical Use Cases

This configuration is required when using:

• VMware / Proxmox / KVM

• Docker / LXC

• Virtual firewalls

• Internal sub-networks

Example:

VM → Main Server → Switch → Internet

The VM never communicates directly with the switch.

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Common Mistakes

❌ Wrong Configuration

Using the network gateway directly:

Gateway: 10.10.10.1

This may cause:

• Packet loss

• IP blocking

• Network shutdown

• Port security violations

✅ Correct Configuration

Gateway: Main Server IP

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Advanced Routing (Optional)

On the main server, IP forwarding must be enabled:

Linux

sysctl -w net.ipv4.ip_forward=1

Persistent:

net.ipv4.ip_forward = 1

in /etc/sysctl.conf

You may also need NAT or static routes depending on your setup.

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Security Notice

Our infrastructure enforces:

• MAC address filtering

• Anti-spoofing rules

• Port security

• Traffic monitoring

Any non-compliant configuration may result in automatic blocking.

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Support & Managed Services

If you are unsure about the configuration, or if you need assistance with:

• Routing

• Virtualization

• Firewall setup

• Network optimization

Our managed services team can provide full support and maintenance.

Please contact us for more information.