# Add Allowed Client Public IP Addresses

When your office network reaches the internet through more than one public IP address, you can tell the phone system which of those addresses are legitimate for staff connecting with the Cloud Voice App (web and desktop). Registering them keeps the system from being surprised when a client's apparent source address changes mid-connection, which is a common cause of failed calls and one-way audio (where one person can hear the other but not the reverse).

:::note
A network with a single public IP address does not need this setup. That address is detected on its own, so there is nothing for you to configure here.
:::

## Before you begin

Your system must be running firmware version **84.22.0.17** or later.

## Add the IP addresses

:::caution
Add every public IP address your office uses to reach the internet. The phone system only trusts the addresses listed here. If a client connects through an address you did not add, its audio can be rejected, which the user experiences as a failed call or one-way audio.
:::

1. Sign in to the phone system web portal and open **Security > Security Settings > Security Options**.
2. Scroll to the **Allowed Client Public IP Address** section.
3. Add each address you want to trust:
   a. Select **Add**.
   b. Type the public IP address, and optionally add a description so you can recognize it later.
   c. Repeat these two steps for every additional address.

   :::tip
   A public IP address is the internet-facing (WAN) address your office presents to the outside world, not the private LAN address (for example, one starting with 192.168) of an individual computer. To find it, open a browser on the office network and search "what is my IP", or ask whoever manages your internet router or firewall.
   :::

   :::note
   You can list up to **10** allowed public IP addresses.
   :::

   ![Allowed Client Public IP Address section with an added address and its description](/images/pbx/public-ip-for-linkus.png)
4. Select **Save**.

## What happens next

Once saved, Cloud Voice App web and desktop clients on your network include every address you listed when they set up a call (in the connection signaling). The phone system then accepts the call's audio (the media stream) arriving from any of those addresses.