General:
Forums subtopic: App & System Services > Networking
TN3151 Choosing the right networking API
Networking Overview document — Despite the fact that this is in the archive, this is still really useful.
TLS for App Developers forums post
Choosing a Network Debugging Tool documentation
WWDC 2019 Session 712 Advances in Networking, Part 1 — This explains the concept of constrained networking, which is Apple’s preferred solution to questions like How do I check whether I’m on Wi-Fi?
TN3135 Low-level networking on watchOS
TN3179 Understanding local network privacy
Adapt to changing network conditions tech talk
Understanding Also-Ran Connections forums post
Extra-ordinary Networking forums post
Foundation networking:
Forums tags: Foundation, CFNetwork
URL Loading System documentation — NSURLSession, or URLSession in Swift, is the recommended API for HTTP[S] on Apple platforms.
Moving to Fewer, Larger Transfers forums post
Testing Background Session Code forums post
Network framework:
Forums tag: Network
Network framework documentation — Network framework is the recommended API for TCP, UDP, and QUIC on Apple platforms.
Building a custom peer-to-peer protocol sample code (aka TicTacToe)
Implementing netcat with Network Framework sample code (aka nwcat)
Configuring a Wi-Fi accessory to join a network sample code
Moving from Multipeer Connectivity to Network Framework forums post
NWEndpoint History and Advice forums post
Network Extension (including Wi-Fi on iOS):
See Network Extension Resources
Wi-Fi Fundamentals
TN3111 iOS Wi-Fi API overview
Wi-Fi Aware framework documentation
Wi-Fi on macOS:
Forums tag: Core WLAN
Core WLAN framework documentation
Wi-Fi Fundamentals
Secure networking:
Forums tags: Security
Apple Platform Security support document
Preventing Insecure Network Connections documentation — This is all about App Transport Security (ATS).
WWDC 2017 Session 701 Your Apps and Evolving Network Security Standards [1] — This is generally interesting, but the section starting at 17:40 is, AFAIK, the best information from Apple about how certificate revocation works on modern systems.
Available trusted root certificates for Apple operating systems support article
Requirements for trusted certificates in iOS 13 and macOS 10.15 support article
About upcoming limits on trusted certificates support article
Apple’s Certificate Transparency policy support article
What’s new for enterprise in iOS 18 support article — This discusses new key usage requirements.
Technote 2232 HTTPS Server Trust Evaluation
Technote 2326 Creating Certificates for TLS Testing
QA1948 HTTPS and Test Servers
Miscellaneous:
More network-related forums tags: 5G, QUIC, Bonjour
On FTP forums post
Using the Multicast Networking Additional Capability forums post
Investigating Network Latency Problems forums post
WirelessInsights framework documentation
iOS Network Signal Strength forums post
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
[1] This video is no longer available from Apple, but the URL should help you locate other sources of this info.
Networking
RSS for tagExplore the networking protocols and technologies used by the device to connect to Wi-Fi networks, Bluetooth devices, and cellular data services.
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I’m developing an iOS idle game (guild management). To detect manual device time changes that would break progression, I need a trusted “current real-world time” reference.
I’m considering querying Apple’s NTP host time.apple.com, but I couldn’t find any official guidance about whether third-party apps may use time.apple.com directly (acceptable use, rate limits, whether it’s discouraged, etc.). Apple Developer Support couldn’t provide info and suggested asking on the forums.
Questions:
1. Is it permitted for a third-party iOS app to query time.apple.com via NTP/SNTP (Yes/No or conditional)?
2. If permitted, are there any published or recommended constraints (rate limits, caching, prohibited patterns, commercial app considerations)?
3. If not permitted / not recommended, what is the recommended alternative approach (run our own time service, use public NTP pool, or any Apple-recommended mechanism)?
4. If there is any official document / policy covering this, could you point me to it?
For context: I do not need sub-second accuracy and I do not intend high-frequency polling. If implemented at all, it would be very low frequency (e.g., first launch + once per 24h) with caching and graceful fallback on failure. My main goal is policy clarity rather than implementation details.
Topic:
App & System Services
SubTopic:
Networking
Hi,
I’m implementing a macOS DNS Proxy as a system extension and running into a persistent activation error:
OSSystemExtensionErrorDomain error 9 (validationFailed)
with the message:
extension category returned error
This happens both on an MDM‑managed Mac and on a completely clean Mac (no MDM, fresh install).
Setup
macOS: 15.x (clean machine, no MDM)
Xcode: 16.x
Team ID: AAAAAAA111 (test)
Host app bundle ID: com.example.agent.NetShieldProxy
DNS Proxy system extension bundle ID: com.example.agent.NetShieldProxy.dnsProxy
The DNS Proxy is implemented as a NetworkExtension system extension, not an app extension.
Host app entitlements
From codesign -d --entitlements :- /Applications/NetShieldProxy.app:
xml
com.apple.application-identifier
AAAAAAA111.com.example.agent.NetShieldProxy
<key>com.apple.developer.system-extension.install</key>
<true/>
<key>com.apple.developer.team-identifier</key>
<string>AAAAAAA111</string>
<key>com.apple.security.app-sandbox</key>
<true/>
<key>com.apple.security.application-groups</key>
<array>
<string>group.com.example.NetShieldmac</string>
</array>
<key>com.apple.security.files.user-selected.read-only</key>
<true/>
xml
com.apple.application-identifier
AAAAAAA111.com.example.agent.NetShieldProxy.dnsProxy
<key>com.apple.developer.networking.networkextension</key>
<array>
<string>dns-proxy-systemextension</string>
</array>
<key>com.apple.developer.team-identifier</key>
<string>AAAAAAA111</string>
<key>com.apple.security.application-groups</key>
<array>
<string>group.com.example.NetShieldmac</string>
<string>group.example.NetShieldmac</string>
<string>group.example.agent.enterprise.macos</string>
<string>group.example.com.NetShieldmac</string>
</array>
DNS Proxy system extension Info.plist
On the clean Mac, from:
bash
plutil -p "/Applications/NetShieldProxy.app/Contents/Library/SystemExtensions/com.example.agent.NetShieldProxy.dnsProxy.systemextension/Contents/Info.plist"
I get:
json
{
"CFBundleExecutable" => "com.example.agent.NetShieldProxy.dnsProxy",
"CFBundleIdentifier" => "com.example.agent.NetShieldProxy.dnsProxy",
"CFBundleName" => "com.example.agent.NetShieldProxy.dnsProxy",
"CFBundlePackageType" => "SYSX",
"CFBundleShortVersionString" => "1.0.1.8",
"CFBundleSupportedPlatforms" => [ "MacOSX" ],
"CFBundleVersion" => "0.1.1",
"LSMinimumSystemVersion" => "13.5",
"NSExtension" => {
"NSExtensionPointIdentifier" => "com.apple.dns-proxy",
"NSExtensionPrincipalClass" => "com_example_agent_NetShieldProxy_dnsProxy.DNSProxyProvider"
},
"NSSystemExtensionUsageDescription" => "SYSTEM_EXTENSION_USAGE_DESCRIPTION"
}
The DNSProxyProvider class inherits from NEDNSProxyProvider and is built in the system extension target.
Activation code
In the host app, I use:
swift
import SystemExtensions
final class SystemExtensionActivator: NSObject, OSSystemExtensionRequestDelegate {
private let extensionIdentifier = "com.example.agent.NetShieldProxy.dnsProxy"
func activate(completion: @escaping (Bool) -> Void) {
let request = OSSystemExtensionRequest.activationRequest(
forExtensionWithIdentifier: extensionIdentifier,
queue: .main
)
request.delegate = self
OSSystemExtensionManager.shared.submitRequest(request)
}
func request(_ request: OSSystemExtensionRequest,
didFailWithError error: Error) {
let nsError = error as NSError
print("Activation failed:", nsError)
}
func request(_ request: OSSystemExtensionRequest,
didFinishWithResult result: OSSystemExtensionRequest.Result) {
print("Result:", result.rawValue)
}
}
Runtime behavior on a clean Mac (no MDM)
config.plist is created under /Library/Application Support/NetShield (via a root shell script).
A daemon runs, contacts our backend, and writes /Library/Application Support/NetShield/state.plist with a valid dnsToken and other fields.
The app NetShieldProxy.app is installed via a notarized, stapled Developer ID .pkg.
The extension bundle is present at:
/Applications/NetShieldProxy.app/Contents/Library/SystemExtensions/com.example.agent.NetShieldProxy.dnsProxy.systemextension.
When I press Activate DNS Proxy in the UI, I see in the unified log:
text
NetShieldProxy: [com.example.agent:SystemExtensionActivator] Requesting activation for system extension: com.example.agent.NetShieldProxy.dnsProxy
NetShieldProxy: [com.example.agent:SystemExtensionActivator] SystemExtensionActivator - activation failed: extension category returned error (domain=OSSystemExtensionErrorDomain code=9)
NetShieldProxy: [com.example.agent:SystemExtensionActivator] SystemExtensionActivator - OSSystemExtensionError code enum: 9
NetShieldProxy: [com.example.agent:SystemExtensionActivator] SystemExtensionActivator - validationFailed
And:
bash
systemextensionsctl list
-> 0 extension(s)
There is no prompt in Privacy & Security on this clean Mac.
Question
Given:
The extension is packaged as a system extension (CFBundlePackageType = SYSX) with NSExtensionPointIdentifier = "com.apple.dns-proxy".
Host and extension share the same Team ID and Developer ID Application cert.
Entitlements on the target machine match the provisioning profile and Apple’s docs for DNS Proxy system extensions (dns-proxy-systemextension).
This is happening on a clean Mac with no MDM profiles at all.
What are the likely reasons for OSSystemExtensionErrorDomain error 9 (validationFailed) with "extension category returned error" in this DNS Proxy system extension scenario?
Is there any additional configuration required for DNS Proxy system extensions (beyond entitlements and Info.plist) that could trigger this category-level validation failure?
Any guidance or examples of a working DNS Proxy system extension configuration (host entitlements + extension Info.plist + entitlements) would be greatly appreciated.
Thanks!
When installing a new version the app while a tunnel is connected, seemingly the old packet tunnel process gets stopped but the new one does not come back up. Reportedly, a path monitor is reporting that the device has no connectivity. Is this the expected behavior?
When installing an update from TestFlight or the App store, the packet tunnel instance from the old tunnel is stopped, but, due to the profile being on-demand and incldueAllNetworks, the path monitoring believes the device has no connectivity - so the new app is never downloaded. Is this the expected behavior?
During development, the old packet tunnel gets stopped, the new app is installed, but the new packet tunnel is never started. To start it, the user has to toggle the VPN twice from the Settings app. The tunnel could be started from the VPN app too, if we chose to not take the path monitor into account, but then the user still needs to attempt to start the tunnel twice - it only works on the second try. As far as we can tell, the first time around, the packet tunnel never gets started, the app receives an update about NEVPNStatus being set to disconnecting yet NEVPNConnection does not throw.
The behavior I was naively expecting was that the packet tunnel process would be stopped only when the new app is fully downloaded and when the update is installed, Are we doing something horribly wrong here?
I want to know the right way/API/usage to use NWConnectionGroup to send both datagram and non-datagram stream.
I am currently working on an P2P video streaming app. I want to leverage NWConnectionGroup over QUIC to handle both message channel (traditionally handled by a TCP connection) and media channel (traditionally handled by sth. over UDP) to transmit SRT packets back and forth.
I created a NWConnectionGroup and it worked fine on non-datagram parts. The problems are with datagram part. I tried
extracting a connection with datagram = true either from the group or from message, doesn't and in some cases it breaks other non-datagram connections.
I currently send datagram directly using the NWConnectionGroup.send(content:completion). It kinda works but I keep seeing it canceled a lot of messages, which breaks SRT shortly after start. The warnings belong flooded my console. (Seems like want me to create a connection to transmit datagram, how?)
nw_connection_create_with_connection [C1600] Original connection not yet connected
nw_connection_group_create_connection_for_endpoint_and_parameters [G1] failed to create connection with parameters quic, local: fe80::439:68b4:6ec2:694%en0.60517, definite, attribution: developer, server
I must use it in wrong way. What should I do to fix it?
I have an app that has been using the following code to down load audio files:
if let url = URL(string: episode.fetchPath()) {
var request = URLRequest(url: url)
request.httpMethod = "get"
let task = session.downloadTask(with: request)
And then the following completionHandler code:
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
try FileManager.default.moveItem(at: location, to: localUrl)
In the spirit of modernization, I'm trying to update this code to use async await:
var request = URLRequest(url: url)
request.httpMethod = "get"
let (data, response) = try await URLSession.shared.data(for: request)
try data.write(to: localUrl, options: [.atomicWrite, .completeFileProtection])
Both these code paths use the same url value. Both return the same Data blobs (they return the same hash value)
Unfortunately the second code path (using await) introduces a problem. When the audio is playing and the iPhone goes to sleep, after 15 seconds, the audio stops. This problem does not occur when running the first code (using the didFinish completion handler)
Same data, stored in the same URL, but using different URLSession calls. I would like to use async/await and not have to experience the audio ending after just 15 seconds of the device screen being asleep. any guidance greatly appreciated.
Topic:
App & System Services
SubTopic:
Networking
Tags:
Files and Storage
Network
CFNetwork
Background Tasks
Hello,
I have an app that is using iOS 26 Network Framework APIs.
It is using QUIC, TLS 1.3 and Bonjour. For TLS I am using a PKCS#12 identity.
All works well and as expected if the devices (iPhone with no cellular, iPhone with cellular, and iPad no cellular) are all on the same wifi network.
If I turn off my router (ie no more wifi network) and leave on the wifi toggle on the iOS devices - only the non cellular iPhone and iPad are able to discovery and connect to each other. My iPhone with cellular is not able to.
By sharing my logs with Cursor AI it was determined that the connection between the two problematic peers (iPad with no cellular and iPhone with cellular) never even makes it to the TLS step because I never see the logs where I print out the certs I compare.
I tried doing "builder.requiredInterfaceType(.wifi)" but doing that blocked the two non cellular devices from working. I also tried "builder.prohibitedInterfaceTypes([.cellular])" but that also did not work.
Is AWDL on it's way out? Should I focus my energy on Wi-Fi Aware?
Regards,
Captadoh
Hi everyone 👋
As a network engineer and indie iOS developer, I couldn’t find a lightweight mobile tool that fully supports IPv4/IPv6 dual-stack diagnostics — so I built NetToolbox -All-In-One Utility for engineers, DevOps, and developers.
Here are its core features that solve real mobile networking pain points:
One-Click Full Diagnostics: Integrates ping, traceroute, and multi-type DNS queries (A/AAAA/CNAME) — no need to switch between apps
IPv4/IPv6 Dual-Stack Support: Seamlessly works in IPv6-only networks, with the ability to test connectivity differences between dual-stack environments
LAN Device Scanning: Quickly identifies all devices on the same network segment and checks port availability
Offline Functionality: Diagnostic logic is stored locally, enabling LAN troubleshooting without an internet connection
Lightweight Design: 5MB install size, no storage bloat, and low power consumption during operation
Dark Mode Support: Tailored for developers who work late at night
During development, I leveraged Apple Intelligence alongside Claude Code and Gemini 3 to accelerate the process, optimize iOS native networking stack adaptation and local storage logic, and significantly boost development efficiency.
I’d love to hear from the community:
What must-have features are missing from mobile network diagnostic tools?
Do you have experience optimizing iOS workflows with Apple Intelligence?
👉 You can try the app here:
https://apps.apple.com/us/app/nettoolbox-all-in-one-utility/id6757392404
Feedback is highly appreciated — I’ll keep iterating to make it better! 🚀
Topic:
App & System Services
SubTopic:
Networking
Tags:
Developer Tools
Network Extension
Network
Apple Intelligence
Apple supports Wi‑Fi Aware, but it’s not clear what channel bandwidth Apple’s Wi‑Fi Aware uses. Is it 80 MHz or 40 MHz? Also, what is the channel bandwidth used by AirDrop?
Hello,
is there a way to get MCC/MNC carrier codes on iOS? I'm also wondering if there's a private API.
I want to obtain network information while I am abroad to determine the country of residence.
We've often observed connectivity issues from our VPN app that can only be remedied by removing the VPN profile. It happens to a small but significant amount of our users, this often happens more when the app is updated, but the VPN profile corruption can happen without that too.
The behavior we're observing is that any socket opened by the packet tunnel process just fails to send any data whatsoever. Stopping and restarting the packet tunnel does not help. The only solution is to remove the profile and create a new one. We believe our app is not the only one suffering from this issue as other VPN apps have added a specific button to refresh their VPN profile, which seemingly deletes and re-created the VPN configuration profile. Previously, we've caught glimpses of this in a sysdiagnose, but that was a while ago and we found nothing of interest. Alas, the sysdiagnose was not captured on a device with the network extension diagnostic profile (it was not a developer device).
I would love to get technical support with this, as our bug reports have gone unanswered for long enough, yet we are still struggling with this issue. But of course, there is no minimum viable xcodeproject that reproduces this. Is there anything we can feasibly do to help with this issue? Is it even an acknowledged issue?
Hey there
Are there any recommendations or guidance for apps on alternatives to certificate pinning to secure their device network traffic?
I want to move away from the overhead and risk associated with rotating certificates when using leaf pinning.
However, I also don't want people to be able to perform a MITM attack easily using something like Charles Proxy with a self‑signed certificate added to the trust store.
My understanding is that an app cannot distinguish between user‑trusted certificates and system‑trusted certificates in the trust store, so it cannot block traffic that uses user‑trusted certificates.
Topic:
App & System Services
SubTopic:
Networking
cant open this website: https://appstoreconnect.apple.com/apps
Bad Gateway
Correlation Key: EJMQBY3TQQI6QR2RBCFRFK7WSM
Topic:
App & System Services
SubTopic:
Networking
I added a Content Filter to my app, and when running it in Xcode (Debug/Release), I get the expected permission prompt:
"Would like to filter network content (Allow / Don't Allow)".
However, when I install the app via TestFlight, this prompt doesn’t appear at all, and the feature doesn’t work.
Is there a special configuration required for TestFlight? Has anyone encountered this issue before?
Thanks!
We have a Java application built for macOS. On the first launch, the application prompts the user to allow local network access. We've correctly added the NSLocalNetworkUsageDescription key to the Info.plist, and the provided description appears in the system prompt.
After the user grants permission, the application can successfully connect to a local server using its hostname. However, the issue arises after the system is rebooted. When the application is launched again, macOS does not prompt for local network access a second time—which is expected, as the permission was already granted.
Despite this, the application is unable to connect to the local server. It appears the previously granted permission is being ignored after a reboot. A temporary workaround is to manually toggle the Local Network permission off and back on via System Settings > Privacy & Security, which restores connectivity—until the next reboot.
This behavior is highly disruptive, both for us and for a significant number of our users. We can reproduce this on multiple systems...
The issues started from macOS Sequoia 15.0
By opening the application bundle using "Show Package Contents," we can launch the application via "JavaAppLauncher" without any issues. Once started, the application is able to connect to our server over the local network. This seems to bypass the granted permissions? "JavaAppLauncher" is also been used in our Info.plist file
For a long time our app had this creation of a URLRequest:
var urlRequest = URLRequest(url: url, cachePolicy: .reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: timeout)
But since iOS 26 was released we started to get crashes in this call. It is created on a background thread.
Thread 10 Crashed:
0 libsystem_malloc.dylib 0x00000001920e309c _xzm_xzone_malloc_freelist_outlined + 864 (xzone_malloc.c:1869)
1 libswiftCore.dylib 0x0000000184030360 swift::swift_slowAllocTyped(unsigned long, unsigned long, unsigned long long) + 56 (Heap.cpp:110)
2 libswiftCore.dylib 0x0000000184030754 swift_allocObject + 136 (HeapObject.cpp:245)
3 Foundation 0x00000001845dab9c specialized _ArrayBuffer._consumeAndCreateNew(bufferIsUnique:minimumCapacity:growForAppend:) + 120
4 Foundation 0x00000001845daa58 specialized static _SwiftURL._makeCFURL(from:baseURL:) + 2288 (URL_Swift.swift:1192)
5 Foundation 0x00000001845da118 closure #1 in _SwiftURL._nsurl.getter + 112 (URL_Swift.swift:64)
6 Foundation 0x00000001845da160 partial apply for closure #1 in _SwiftURL._nsurl.getter + 20 (<compiler-generated>:0)
7 Foundation 0x00000001845da0a0 closure #1 in _SwiftURL._nsurl.getterpartial apply + 16
8 Foundation 0x00000001845d9a6c protocol witness for _URLProtocol.bridgeToNSURL() in conformance _SwiftURL + 196 (<compiler-generated>:974)
9 Foundation 0x000000018470f31c URLRequest.init(url:cachePolicy:timeoutInterval:) + 92 (URLRequest.swift:44)# Live For Studio
Any idea if this crash is caused by our code or if it is a known problem in iOS 26?
I have attached one of the crash reports from Xcode:
2025-10-08_10-13-45.1128_+0200-8acf1536892bf0576f963e1534419cd29e6e10b8.crash
Why is the WiFiAware framework not importable in Mac Catalyst? Are there any plans to support Wi-Fi Aware technology on Mac Catalyst in the future?
As part of the OpenJDK testing we run several regression tests, including for Java SE networking APIs. These APIs ultimately end up calling BSD socket functions. On macos, starting macos 26, including on recent 26.2 version, we have started seeing some unexplained but consistent exception from one of these BSD socket APIs. We receive a "ENOBUFS" errno (No buffer space available) when trying to construct a socket(). These exact same tests continue to pass on many other older versions of macos (including 15.7.x). After looking into this more, we have been able to narrow this down to a very trivial C code which is as follows (also attached):
#include <stdio.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <sys/errno.h>
static int create_socket(const int attempt_number) {
const int fd = socket(AF_INET6, SOCK_STREAM, 0);
if (fd < 0) {
fprintf(stderr, "socket creation failed on attempt %d,"
" due to: %s\n", attempt_number, strerror(errno));
return fd;
}
return fd;
}
int main() {
const unsigned int num_times = 250000;
for (unsigned int i = 1; i <= num_times; i++) {
const int fd = create_socket(i);
if (fd < 0) {
return -1;
}
close(fd);
}
fprintf(stderr, "successfully created and closed %d sockets\n", num_times);
}
The code very trivially creates a socket() and close()s it. It does this repeatedly in a loop for a certain number of iterations.
Compiling this as:
clang sockbufspaceerr.c -o sockbufspaceerr.o
and running it as:
./sockbufspaceerr.o
consistently generates an error as follows on macos 26.x:
socket creation failed on attempt 160995, due to: No buffer space available
The iteration number on which the socket() creation fails varies, but the issue does reproduce. Running the same on older versions of macos doesn't reproduce the issue and the program terminates normally after those many iterations.
Looking at the xnu source that is made available for each macos release here https://opensource.apple.com/releases/, I see that for macos 26.x there have been changes in this kernel code and there appears to be some kind of memory accountability code introduced in this code path. However, looking at the reproducer/application code in question, I believe it uses the right set of functions to both create as well as release the resources, so I can't see why this should cause the above error in macos 26.x.
Does this look like some issue that needs attention in the macos kernel and should I report it through feedback assitant tool?
Currently in our app, to identify a network switch in device we are doing NEHotspotHelper.register and then NEHotspotHelperHandler block. When the command type is evaluate and if the network.didJustJoin, we are identifying it as a network switch.
As a part of moving our code base to iOS 26, if is found that NEHotspotHelper is deprecated. What is the proper replacement for this?
Topic:
App & System Services
SubTopic:
Networking
My application needs local network access. When it is started for the first time, the user gets a prompt to enable local network access (as expected). The application is then shown as enabled in Privacy & Security / Local Network and local network access is working.
If macOS is then shutdown and restarted, local network access is blocked for the application even though it is still shown as enabled in Privacy & Security / Local Network. Local network access can be restored either by toggling permission off and on in Privacy & Security / Local Network or by disabling and enabling Wi-Fi.
This behaviour is consistent on Sequoia 15.1. It happens sometimes on 15.0 and 15.0.1 but not every time. Is my application doing something wrong or is this a Sequoia issue? If it is a Sequoia issue, is there some change I can make to my application to work around it?
Description
Enterprise users are experiencing VPN resource access failures after upgrading to macOS Tahoe. Investigation indicates that configd (specifically IPMonitor) is incorrectly re-ranking network interfaces after a connectivity failure with probe server. This results in DNS queries routing through the physical network adapter (en0) instead of the VPN virtual adapter, even while the tunnel is active. This behaviour is not seen in previous macOS versions.
Steps to Reproduce:
Connect to an enterprise VPN (e.g., Ivanti Secure Access).
Trigger a transient network condition where the Apple probe server is unreachable. For example make the DNS server down for 30 sec.
Observe the system routing DNS queries for internal resources to the physical adapter.
Expected Results The: VPN virtual interface should maintain its primary rank for enterprise DNS queries regardless of the physical adapter's probe status.
Actual Results: IPMonitor detects an UplinkIssue, deprioritizes the VPN interface, and elevates the physical adapter to a higher priority rank.
Technical Root Cause & Logs:
The system logs show IPMonitor identifying an issue and modifying the interface priority at 16:03:54:
IPMonitor Detection: The process identifies an inability to reach the Apple probe server and marks en0 with an advisory:
Log snippet
2026-01-06 16:03:53.956399+0100 localhost configd[594]: [com.apple.SystemConfiguration:IPMonitor] configd[594] SetInterfaceAdvisory(en0) = UplinkIssue (2) reason='unable to reach probe server'
Interface Re-ranking: Immediately following, IPMonitor recalculates the rank, placing the physical service ID at a higher priority (lower numerical rank) than the VPN service ID (net.pulsesecure...):
Log snippet
2026-01-06 16:03:53.967935+0100 localhost configd[594]: [com.apple.SystemConfiguration:IPMonitor] 0. en0 serviceID=50CD9266-B097-4664-BFE6-7BAFCC5E9DC0 addr=192.168.0.128 rank=0x200000d
2026-01-06 16:03:53.967947+0100 localhost configd[594]: [com.apple.SystemConfiguration:IPMonitor] 1. en0 serviceID=net.pulsesecure.pulse.nc.main addr=192.168.0.128 rank=0x2ffffff
3.Physical adapter Is selected as Primary Interface:
2026-01-06 16:03:53.968145+0100 localhost configd[594]: [com.apple.SystemConfiguration:IPMonitor] 50CD9266-B097-4664-BFE6-7BAFCC5E9DC0 is the new primary IPv4
configd[594]: 50CD9266-B097-4664-BFE6-7BAFCC5E9DC0 is the new primary DNS
Packet Trace Evidence Wireshark confirms that DNS queries for enterprise-specific DNS servers are being originated from the physical IP (192.168.0.128) instead of the virtual adapter:
Time: 16:03:54.084
Source: 192.168.0.128 (Physical Adapter)
Destination: 172.29.155.115 (Internal VPN DNS Server)
Result: Connectivity Failure (Queries sent outside the tunnel)
Topic:
App & System Services
SubTopic:
Networking