Security settings

There are a number of security settings you can customize on your CenturyLink modem:

Administrator password

Application forwarding

Port forwarding

DMZ hosting

IPv4 or IPv6 firewall

NAT (Network Address Translation)

UPnP (Universal Plug n Play)

SIP (Session Initiation Protocol) ALG

You'll find security settings under Advanced Setup options, then Security.

Click the options below to see step-by-step instructions for each setting.

Application Forwarding allows you to forward a subset of programs to selected devices connected to your network.

Select Application Forwarding in the left sidebar, under Security.

Follow the steps to edit the Application Forwarding settings.

Step 1: Set the device you want to forward to, either by selecting it from the dropdown or by entering the IP address.
Step 2: Select the application category and specific application to be forwarded.
Step 3: Click "Apply" to save your changes.

Port Forwarding allows you to enter ports or port ranges to enable forwarding of internet applications from your modem to a device connected to your network.

Select Port Forwarding in the left sidebar.

Follow the steps to edit the Port Forwarding settings.

Step 1: Designate the device you want to forward to, either by selecting from the dropdown or entering the device's IP address.

Step 2: Enter the LAN port information (starting and ending port).

Step 3: Select the correct protocol.

Step 4: Choose "All IP Addresses" or define a specific IP address. You can review and remove entries from the Port Forwarding List at the bottom.

Step 5: When you're finished adding or removing entries, click "Apply" to save your changes.

DMZ hosting enables a LAN device to use the modem WAN IP address as its own. DMZ places the LAN device outside the firewall.

Select DMZ Hosting in the left sidebar.

Follow the steps to edit the DMZ Hosting settings.

Step 1: Enable DMZ.
Step 2: Select the device from the dropdown or manually enter the device's IP address.
Step 3: Click "Apply" to save your changes.

Activating the firewall on your modem is optional. When the firewall is enabled, the security of your network is enhanced, but some network functionality will be lost.

Select IPv4 Firewall or IPv6 Firewall in the left sidebar.

About "Stealth Mode": Stealth mode prevents the router from responding to probing requests. The router will still answer incoming requests for authorized apps. Unexpected requests, such as ICMP (ping) are ignored. Do not enable Stealth Mode unless you understand the technical impacts.

IPv4 firewall

Follow the steps to set up the IPv4 firewall.

Step 1: Enable/Disable stealth mode. Do not enable stealth mode unless you fully understand the impact.
Step 2: Set the IP address or addressing type to which the firewall will apply.
Step 3: Set the firewall security level.
Step 4: Make selections in the firewall table (sample shown below) to allow or block different kinds of incoming and outgoing traffic.
Step 5: When you're finished modifying the rules, click "Apply" to save your changes.

IPv6 firewall

Follow the steps to set up the IPv6 firewall.

Step 1: Enable/Disable stealth mode. Do not enable stealth mode unless you fully understand the impact.
Step 2: Enable the firewall.
Step 3: Choose to allow/block incoming and outgoing traffic on the network.
Step 4: Click "Apply" to save your changes.

Network Address Translation (NAT) is an advanced networking setting that most people do not use. We advise you not to disable NAT unless instructed to do so by a qualified technician, as it could open your broadband modem to outside intrusion and create a security risk.

Select NAT in the left sidebar.

Follow the steps to edit the NAT settings.

Step 1: Enable/Disable NAT (we suggest keeping enabled unless advised to do so by a qualified tech)

CenturyLink recommends that you keep NAT enabled. Changes to this feature will reset some of the other settings on the modem. Do not proceed without understanding the technical impacts of using this feature.

Step 2: Click "Apply" to save your changes.

Universal Plug and Play (UPnP) allows devices on the modem network to discover each other and establish sharing and communications. Devices that commonly use UPnP are printers, media servers, IP cameras, smart TVs and gaming systems.

Select UPnP in the left sidebar.

Follow the steps to edit the UPnP settings.

Step 1: Enable/Disable UPnP.

Step 2: Enable/Disable the UPnP NAT-T state. You can also view the list below.

Step 3: Click "Apply" to save your changes.

Session Initiation Protocol (SIP) is a communication standard used in VolP (Voice over IP) networks. SIP ALG refers to a gateway tool that enables or disables the modem to pass SIP sessions to the local area network (LAN).

Select IP ALG in the left sidebar.