Matt? Quinn? Any thoughts on this? When I setup the NWUdpSession for LTE, for the source address, I get the IP address of 192.0.0.1. Always. On any phone I try this with. Whereas, with Verizon, we get a random IP for LTE, like 100.105.38.96. On Android, we don't bind to a local IP address, we bind to a transport type, e.g. Wi-Fi or LTE. I am wondering if there is a similar option in iOS.

(Update) From what I am reading, the issue is likely because T-Mobile requires ipv6 only support. When I setup the tunnel, I do provide both v4 and v6 endpoints, but when setting up the individual links, I can only specify a single local IP address (v4 or v6). Can someone explain how to setup a NWUdpSession that supports both v4 and v6, or it that is even the right thing to do? Tunnel: tunSettings.ipv4Settings = NEIPv4Settings(addresses: [ip4Address], subnetMasks: ["255.255.255.0"]) tunSettings.ipv4Settings?.includedRoutes = [NEIPv4Route.default()] tunSettings.ipv6Settings = NEIPv6Settings(addresses: [ip6Address], networkPrefixLengths: [124 as NSNumber]) tunSettings.ipv6Settings?.includedRoutes = [NEIPv6Route.default()] Links: let src = NWHostEndpoint(hostname: link.ipv4!, port: String(link.port)) link.udpSession = self.createUDPSession(to: dest, from: src)

This is how the console looks when it works (Verizon) default 14:56:05.737875-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 14:56:05.738353-0600 IWiNS-Tunnel nw_connection_report_state_with_handler_on_nw_queue [C4] reporting state preparing default 14:56:05.739279-0600 IWiNS-Tunnel nw_flow_connected [C4 IPv4#6942181e:8091 in_progress channel-flow (satisfied (Path is satisfied), interface: pdp_ip0, scoped, ipv4, ipv6, dns, expensive)] Output protocol connected default 14:56:05.739496-0600 IWiNS-Tunnel nw_connection_report_state_with_handler_on_nw_queue [C4] reporting state ready default 14:56:05.739645-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 14:56:05.739684-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Ready. default 14:56:05.739764-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (IsViable) - LTE. IsViable: true.

Here is a relevant section from the console: default 12:18:46.628081-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 initial path ((null))] event: path:start @0.000s default 12:18:46.628137-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 12:18:46.628679-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 waiting path (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: path:unsatisfied @0.000s, uuid: 80574970-6F25-4388-8936-6809DEF1A02C default 12:18:46.628741-0600 IWiNS-Tunnel nw_connection_report_state_with_handler_on_nw_queue [C618] reporting state waiting default 12:18:46.628978-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 in_progress resolver (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: resolver:start_dns @0.001s default 12:18:46.629035-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 12:18:46.629092-0600 IWiNS-Tunnel nw_connection_report_state_with_handler_on_nw_queue [C618] reporting state preparing default 12:18:46.629247-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Waiting. default 12:18:46.629465-0600 mDNSResponder [R39862] DNSServiceCreateConnection START PID[1594](IWiNS-Tunnel) default 12:18:46.629714-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Waiting. default 12:18:46.629961-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 12:18:46.630305-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 in_progress resolver (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: resolver:receive_dns @0.002s default 12:18:46.630402-0600 mDNSResponder [R39862] DNSServiceCreateConnection STOP PID[1594](IWiNS-Tunnel) default 12:18:46.630884-0600 IWiNS-Tunnel [C618.1 IPv4#5aa006fc:8091 initial path ((null))] event: path:start @0.002s default 12:18:46.631225-0600 IWiNS-Tunnel [C618.1 IPv4#5aa006fc:8091 waiting path (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: path:unsatisfied @0.003s, uuid: 359E2D37-59A9-4025-93E2-7B2D52986999 default 12:18:46.631548-0600 IWiNS-Tunnel [C618.1 IPv4#5aa006fc:8091 failed path (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: null:null @0.003s default 12:18:46.631696-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 failed resolver (unsatisfied (No network route), interface: pdp_ip0, dns, expensive)] event: resolver:children_failed @0.003s default 12:18:46.631773-0600 IWiNS-Tunnel nw_connection_report_state_with_handler_on_nw_queue [C618] reporting state failed error Network is down default 12:18:46.632093-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Preparing. default 12:18:46.632160-0600 IWiNS-Tunnel iwins->tunnel: UDPSession Observer callback (State) - LTE. New State: Failed. default 12:18:46.632241-0600 IWiNS-Tunnel iwins->tunnel: *** Failed Link: LTE *** default 12:18:46.632327-0600 IWiNS-Tunnel iwins->tunnel: Stopping KVO observers default 12:18:46.632405-0600 IWiNS-Tunnel [C618 E0D68D17-6E75-4CDC-84F1-74CC16AD1AF0 IPv4#5aa006fc:8091 udp, local: 192.0.0.1:59831] cancel default 12:18:46.632482-0600 IWiNS-Tunnel [C618 IPv4#5aa006fc:8091 udp, local: 192.0.0.1:59831] cancelled

We would be interested as well to see the suggested improvements from Apple, as we have the same concerns. Can someone post this?