Here is the FB No. FB22589442

I wasn’t able to find an equivalent bug for DHCP reservations, so I recommend that your file your own about that. I think i wont file the bug since it is not a bug and it is by design it is clearly documented here https://developer.apple.com/documentation/vmnet/vmnet_network_configuration_add_dhcp_reservation(_:_:_:)?language=objc

utm app uses this method https://github.com/utmapp/UTM/blob/30c8202c630c5af2e3c3403df1bb95c962459bc6/Services/UTMASIFImage.m#L18 is it allowed in sandboxed environment?

now it fails in 26.5 beta 2 with operation not permitted error. I am not sure why apple keep introducing new bugs for this feature. we cant rely on this method at all. need a better stable way for creating asif disk programmatically. apple keeps breaking things . what will happen to live applications on appstore. i am very disappointed Update: Downlaoded xcode 26.5 and it seems to be fixed the problem. sorry about the above post

My understanding is that software running on the host Mac is unable to connect to a server running on the VM via the public port (8000), even though you have forwarding configured in vmnet. Have you tried doing the same from some other machine on the host’s network, so X in this case? Wow. that worked. If i try to access from computer x in my host network with the ip address of the host:8000 it worked. when i try the same in the host itlsef with localhost or host ip it is not working. Is this is the way by design. Why it is not working if i do it from the host itself strange. Do i need to make some changes for this to work. Please enlighten me. thank you very much Now i know the port forwarding api is working as exected witht the limitation of not able to access the public port 8000 from the host itself.

I tried to manually port forward using pfctl temporarily and found that it also does not work for the scenario. But i found that reaching http://guestip:port worked fine. not sure is there any check i have to do at os level to make it work.

still I am interested in discovering the IP for bdridged & default nat networking as the title says. If i need to the port forwarding without static ip i need this the default nat network. and also diplaying the ip address in the app is very useful info for the user. the user dont need to dig into the guest for this.

Is that a realistic user scenario that you’re trying to support? You are correct—this is exactly the scenario I am trying to implement. The primary challenge is that the network configuration cannot be modified while it is active. Currently, when a user attempts to change the network settings while it is in use, I prompt them either to restart the application or to stop any virtual machines using the network. This allows me to properly clean up and recreate the network with the updated configuration. At this stage, I have chosen to require an application restart for network modifications, as I have not found a reliable method to fully release the vmnet network. The documentation suggests using CFRelease, but this is not directly compatible with ARC. I did identify a workaround that appears to function correctly; however, the limitation remains that the network configuration cannot be changed while it is active. Additionally, it is not possible to hot-plug or remove network attachments from a running virtual machine, which further constrains dynamic reconfiguration. Given this, my current focus has shifted to resolving the port forwarding issue. Even when the configuration is predefined, port forwarding is not functioning as expected, despite the API call returning success. I am investigating why this discrepancy is occurring. This is where i need help. Instead of ip discovery i asked the user to set static ip which i can get it work with dhcp reservation with the network.

[quote='884370022, DTS Engineer, /thread/822658?answerId=884370022#884370022'] ard to say without more context. Specifically: [/quote] The guest acquiring the ip address correct for test i have created web server on the guest listen on port 5264 when i try to acces the port directly with the ip address of the guest it is working. i can reach the guest ip from the host with the port 5264. so i forward port 8000 of host as external port in the sample code what i have provided and i access http://localhost:8000 on the host and it does not work. Hope i have give enough details.

[quote='884369022, DTS Engineer, /thread/822025?answerId=884369022#884369022'] Why is that? [/quote] Let me explain i present a settings screen where the user can define their own networks with their own subnet. After that the user can pick up the desired network in vm creation. So i allow the user to share the same network for various virtual machine. It is a user choice who decide which netwotk the vm belong to.

I tried creating new vmnet config and vmnet network for the second vm with same subnet and it failed. It seems to be we cant use the same subnet for new vmnet network. if i provide different subnet it is working fine. But i dont want to have a different subnet for each vm. I think we cant use vmnet_interfce_start_with_network because this is being taken care by the mac os virtuliaztion framewoth with the network we provide. any how i tried this it crashes with bad acces

[quote='884231022, DTS Engineer, /thread/822025?answerId=884231022#884231022'] Coming back to your IP address issue, [/quote] Sorry i was confused between network and interface how to create a new interface should i use this https://developer.apple.com/documentation/vmnet/vmnet_interface_start_with_network(::::) ?

Ok now i found how to do port forwarding also i used this code var ipAddr = in_addr() // 1. Convert String to in_addr inet_pton(AF_INET, guestIP, &ipAddr) let status = vmnet_network_configuration_add_port_forwarding_rule( config, UInt8(IPPROTO_TCP), // TCP protocol sa_family_t(AF_INET), // address family guestPort, // internal port (guest) externalPort, // external port (host) &ipAddr // internal address (guest IP) ) if status == .VMNET_SUCCESS { print("✅ Port Forwarding set: Mac:\(externalPort) -> VM(\(guestIP)):\(guestPort)") } else { print("❌ Port Forwarding failed for \(guestIP): \(status.rawValue)") } } for port forwding it is returning success but when i test it it does not work. Is there anything i am doing wrong? Please help me also in fixing this problem

my code looks likes this import Virtualization import vmnet import Darwin @available(macOS 26.0, *) public class SharedVMNetManager { public static let shared = SharedVMNetManager() private var activeNetwork: vmnet_network_ref? private var activeConfig: vmnet_network_configuration_ref? // Track which MACs we have already told the kernel about private var registeredMacs: Set<String> = [] private let lock = NSLock() private init() {} public func getAttachment(macAddress: String, reservedIP: String) -> VZVmnetNetworkDeviceAttachment? { lock.lock() defer { lock.unlock() } var status: vmnet_return_t = .VMNET_SUCCESS // 1. Check if we've already initialized the hardware switch if let config = activeConfig, let network = activeNetwork { // ONLY add the reservation if we haven't done it for this MAC yet if !registeredMacs.contains(macAddress) { addReservation(to: config, mac: macAddress, ip: reservedIP) registeredMacs.insert(macAddress) } return VZVmnetNetworkDeviceAttachment(network: network) } // 2. First-time initialization let mode: vmnet.operating_modes_t = .VMNET_SHARED_MODE guard let config = vmnet_network_configuration_create(mode, &status), status == .VMNET_SUCCESS else { return nil } // Define Subnet var subnet = in_addr(), mask = in_addr() inet_pton(AF_INET, "192.168.142.1", &subnet) inet_pton(AF_INET, "255.255.255.0", &mask) vmnet_network_configuration_set_ipv4_subnet(config, &subnet, &mask) // Define the Pool (Make sure your reserved IP is INSIDE this range) /*var start = in_addr(), end = in_addr() inet_pton(AF_INET, "192.168.142.10", &start) inet_pton(AF_INET, "192.168.142.50", &end) vmnet_network_configuration_set_ipv4_pool(config, &start, &end)*/ // 3. Register the first MAC before the network starts addReservation(to: config, mac: macAddress, ip: reservedIP) registeredMacs.insert(macAddress) // 4. Commit and Create Network guard let network = vmnet_network_create(config, &status), status == .VMNET_SUCCESS else { return nil } self.activeConfig = config self.activeNetwork = network return VZVmnetNetworkDeviceAttachment(network: network) } private func addReservation(to config: vmnet_network_configuration_ref, mac: String, ip: String) { var macAddr = ether_addr() guard let macPtr = ether_aton(mac) else { return } macAddr = macPtr.pointee var ipAddr = in_addr() inet_pton(AF_INET, ip, &ipAddr) // This tells the kernel's DHCP server: "If you see this MAC, give it this IP" let status = vmnet_network_configuration_add_dhcp_reservation(config, &macAddr, &ipAddr) if status != .VMNET_SUCCESS { print("dhcp faliure \(status.rawValue)") } } } For the first virtual machine the ip address is getting reserved but from second vm onwards ip is not getting reserved it gets from dhcp server. this makes me not able to assign ip address to second virtual machine onwards thus we cant determine the ipadddress of second vm onwards. is there a way we can ask vmnet to refresh the config. is it possible? Or the only way is to create the network config with all the ip address on start of the app and take it from there. what if the user creates a new vm. how to handle this kind of situation. thanks in advance

never mind i managed to get the sample code from apple container github repository. now i can reserve a pool of ip address and assign ip address to guest from that. thanks for the heads up. it seem to be that VZVmnetNetworkDeviceAttachment is only avaialble for mac os 26 how can accomplist this with 14 and 15. any idea? And aslo after doing this i would like to do the port forwarding. Any idea how can i accomplish this.