> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/welcome/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/welcome/cloud-networking/best-practice/save-backbone-cost-with-unlimited-port.md).

# Save Backbone Connection Fees with the Unlimited Port

The **Unlimited Port** of Zenlayer Cloud Networking supports higher port rates and comes with **free metro backbone** for network interconnection within the same city. For customers running multiple workloads in one city that frequently interconnect with public clouds, the Unlimited Port significantly reduces backbone connection costs.

## Background Information <a href="#background-information" id="background-information"></a>

* The Unlimited Port is currently available for purchase in the **Singapore** region. Purchasing in Singapore does not limit its connectivity scope — the Unlimited Port's **cross-city connectivity is not affected** and it can still interconnect with other cities.
* The Unlimited Port currently supports **Layer 2 connections** only; Layer 3 connections are not yet supported.
* Within the same city (metro), the following connections built with Unlimited Ports **waive the backbone connection fees**:
  * **Unlimited Port to Unlimited Port** — for example, two Unlimited Ports in different data centers in Singapore interconnecting with each other.
  * **Unlimited Port to public cloud** — for example, connecting an Unlimited Port in Singapore to a local access point of AWS, Google Cloud, Alibaba Cloud, and other public clouds.
* For details about the Unlimited Port, see [Create a Port](/welcome/cloud-networking/get-started/create-a-port.md#port-types).

## Scenario <a href="#scenario" id="scenario"></a>

Suppose a customer deploys the following resources within the Singapore metro:

* Servers in Data Center A (connected via an Unlimited Port)
* Servers in Data Center B (connected via an Unlimited Port)
* AWS, Alibaba Cloud, and other public cloud services located in Singapore

With Unlimited Ports, the customer can build the following interconnections:

1. **Metro Unlimited Port interconnection**: The Unlimited Ports in Data Center A and Data Center B interconnect over a Layer 2 connection for high-speed private communication between the two sites. This metro backbone connection **incurs no backbone connection fee**.
2. **Unlimited Port to public cloud**: The Unlimited Port in either data center connects directly to a local public cloud access point for low-latency communication with cloud workloads. This metro connection also **waives the backbone connection fee**.

{% hint style="info" %} <mark style="color:blue;">**Cost comparison**</mark>

<mark style="color:blue;">With a Standard Port, interconnection across data centers and to public clouds traverses the backbone network and incurs backbone connection fees. With an Unlimited Port, as long as both ends are in the same city, these backbone connection fees are waived, greatly reducing the customer's operational cost.</mark>
{% endhint %}

## Benefits <a href="#benefits" id="benefits"></a>

* **Lower cost**: Metro Unlimited Port interconnection and Unlimited Port to public cloud connections both waive backbone connection fees.
* **Higher rate**: The Unlimited Port supports higher port rates for bandwidth-intensive, high-throughput workloads.
* **Flexible networking**: Build metro networks over Layer 2 connections as your business requires, with cross-city connectivity that is not limited by the purchase region.

## Procedures <a href="#procedures" id="procedures"></a>

1. Create an **Unlimited Port** in each data center you want to interconnect. See [Create a Port](/welcome/cloud-networking/get-started/create-a-port.md) for details.
2. Create a Layer 2 connection between the Unlimited Ports, or connect an Unlimited Port to a public cloud access point over a Layer 2 connection. See [Create a Layer 2 Connection](/welcome/cloud-networking/get-started/create-a-layer-2-connection.md) for details.
3. If a public cloud is involved, validate the connection in the public cloud console. See [Validate Connection in Public Cloud](/welcome/cloud-networking/get-started/validate-connection-in-public-cloud.md) for details.