Configure LAN and VPN for AT&T Wi-Fi calling

AT&T Wi-Fi Calling LAN/VPN configurations for routers and modems.

To use AT&T Wi-Fi® Calling, your device must be able to communicate with the AT&T network. If your router’s configuration has been updated, or you’re using a firewall, you may have to update your router settings to support AT&T Wi-Fi Calling.

For help updating router configurations, refer to your router manufacturer's website, or contact your Internet Service Provider.
Allow Internet Protocol Security (IPSec)
Internet Protocol Security is a method of encrypting traffic sent through the internet. It’s used to provide a secure voice and data communication path. Some routers permit IPSec messages to be blocked. AT&T Wi-Fi Calling requires IPSec pass-through to be allowed.

Open data ports 500, 4500, and 143
Ports 500, 4500, and 143 (shown in the table) are used to communicate to the AT&T network and must be set to open.

Data ports
PortTCP or UDPService or protocol nameRFCService name
500UDPWi-Fi Calling5996IKEv2
4500UDPWi-Fi Calling5996IKEv2
143TCPInternet Message Access Protocol (IMAP)3501imap

Set Maximum Transmission Unit (MTU) to 1500
MTU represents the maximum packet size that can be transmitted. Wi-Fi Calling performs best if the MTU is set to 1500.

Update equipment firmware
For best performance, always update modems, routers, and switches to the latest software/firmware versions available. Updates can typically be found on the equipment manufacturer’s website

Wi-Fi Calling Fully Qualified Domain Names (FQDN)
A fully qualified domain name (FQDN) is the domain name for a computer, or other host equipment on the internet. Wi-Fi Calling should be able to traverse the following FQDNs:
Last updated: January 20, 2023