Troubleshoot Apple Connectivity
Understanding Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 27.15.17.56 or an IPv6 address like 2000:d91c:d28a:bb54:f0a9:ca87:8b62:5daf. To verify your address, visit https://test-ipv6.com/. However, for those not well-versed in technology, relaying these addresses or referencing MAC addresses like a9:4d:16:ad:c6:48 can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, particularly for previous issues.
Navigating the World Wide Web
To access a webpage like https://cormier.com, your computer initially communicates with a DNS server to convert the host (cormier) combined with the Top Level Domain (com) of the URL into an IP address like 59.121.50.162. Whenever a web request is sent, your computer and browser include its type, such as: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically configured address received via DHCP. For instance, you may obtain a default gateway like 192.168.114.20 (commonly ending in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic for routing purposes. For a detailed explanation on setting up IPv6, refer to our comprehensive guide how-to-fix-ipv6-connectivity/. Alternatively, you can verify this process on Mac or Linux using the following steps:
IPv4 Routes and the Host IPv4 Route Table (inc. VPN)
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.114.20 UGScg en0 128.0/1 172.18.12.193 UGSc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v4 address space.
IPv6 Routes and the Host IPv6 Route Table (inc. VPN)
netstat -rn -f inet6 | egrep -i "default|2000::/3"
If you have IPv6 active the above should return at least one route (as per below) via a known interface such as “en0 " on a Mac.
default fe80:eb03:bc92:20dc:db9b%en0 UGcg en0 default fe80::%utun0 UGcIg utun0 default fe80::%utun1 UGcIg utun1 default fe80::%utun2 UGcIg utun2 2000::/3 utun3 USc utun3
Note: We are not just looking for the default but also for any VPN that overrides the public v6 address space.
Debugging DHCP for both IPv4 and IPv6
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
...
domain_name_server (ip_mult): {22.180.194.242, 153.142.121.250}
end (none):
...
So, in the above we are not getting IPv6 DNS servers from the DHCPv4 reply but…
ipconfig getv6packet en0
DHCPv6 REPLY (7) Transaction ID 0x80940b Length 76
Options[4] = {
CLIENTID (1) Length 14: DUID LLT HW 1 Time 668691856 Addr a9:4d:16:ad:c6:48
DNS_SERVERS (23) Length 32: 2606:4700:4700::1111, 2001:4860:4860::8844
DOMAIN_LIST (24) Length 0: Invalid
SERVERID (2) Length 10: DUID LL HW 1 Addr b6:cd:98:46:c9:f5
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Troubleshoot Network Issues on Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.11.9, 11.6.3, or 12.1.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that adopt remote work and Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although many of these are point-in-time only in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (despite limited interaction), you can use sudo /usr/bin/sysdiagnose, which will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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