IP Passthrough
Expert function
Swisscom recommends that this function only be configured by experienced IT specialists. Misconfigurations can lead to significant security risks.
IP Passthrough allows all incoming Internet traffic to be forwarded directly to a specific device on the network. The Centro Business receives a public IP address from the Internet and automatically forwards all traffic to the configured client.
Typical use cases
- A dedicated hardware firewall (Sophos, FortiGate, pfSense) should receive and manage all incoming Internet traffic
- A VPN gateway needs to receive all incoming traffic
- A security appliance should analyse traffic before it reaches the internal network
Configure IP Passthrough
In the router portal under Network → Passthrough:
- Activate IP Passthrough
- Connect the device to the dedicated LAN port:
- Centro Business 2.0: LAN Port 1
- Centro Business 3.0: LAN Port 5
Configure external gateway/firewall
Configure the following network settings on the connected device:
| Parameter | Value |
|---|---|
| WAN type | Ethernet with static IP |
| IP address | 172.31.255.6 |
| Subnet mask | 255.255.255.252 |
| Gateway | 172.31.255.5 |
| MTU | 1500 |
Limitations
- Not available with BNS/EC-S contract
- The Centro Business firewall no longer applies to passthrough traffic
- Only one device can use IP Passthrough
FAQ - IP Passthrough
Why does Swisscom declare IP Passthrough as an expert function?
IP Passthrough requires specialised technical knowledge. If downstream devices such as a firewall are not correctly configured, it can lead to attacks on the customer infrastructure. Swisscom recommends using the DMZ function instead to ensure failover protection.
On which Ethernet port is Passthrough activated?
- Centro Business 2.0: LAN Port 1
- Centro Business 3.0: LAN Port 5
What is the difference between IP Passthrough and PPP Passthrough?
- IP Passthrough: The Centro Business establishes the Internet connection and forwards all traffic to the device. Swisscom services (VoIP, TV) remain active on the CB.
- PPP Passthrough: The connected device establishes the PPPoE connection itself and receives the public IP directly. The Centro Business only acts as a bridge.
What MTU size should be configured?
With IP Passthrough, the standard MTU value of 1500 bytes can be set. This ensures smooth and efficient data transmission.
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