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[AT&T Wireless](https://www.att.com/support/wireless/) # Configure LAN and VPN for AT&T Wi-Fi calling AT&T Wi-Fi Calling LAN/VPN configurations for routers and modems. * * * DETAILED INFO 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__ | __Port__ | __TCP or UDP__ | __Service or protocol name__ | __RFC__ | __Service name__ | |----------|----------------|-----------------------------------------|---------|------------------| | __500__ | UDP | Wi-Fi Calling | 5996 | IKEv2 | | __4500__ | UDP | Wi-Fi Calling | 5996 | IKEv2 | | __143__ | TCP | Internet Message Access Protocol (IMAP) | 3501 | imap | __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: - epdg.epc.att.net - sentitlement2.mobile.att.net - vvm.mobile.att.net Last updated: January 20, 2023 * * * ## Browse topics Activation, setup, transfer & unlock Apps, features & voicemail International Network & hotspots Plans & device protection Upgrades, orders & installment plans Ready, set, go! Activate your device, set it up on our network, and transfer your contacts and info. Activate Setup Transfer Unlock ### Was this guide helpful? 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