How To Test Apple Issues
Understanding Internet Addressing
When you’re on the Internet, you are assigned an address, which could be in the form of a Public IPv4 address such as 101.126.61.124 or an IPv6 address like 2000:622a:a0cc:ed53:fe3d:b4f5:5408:98d. A simple way to verify this is by using https://test-ipv6.com/. However, it can be challenging for individuals who are not well-versed in technology to communicate these addresses, or even identify and relay MAC addresses like b0:59:af:b5:32:7b without making errors. Additionally, this method does not provide any historical information, especially regarding past issues.
Navigating the World Wide Web
Accessing a web page such as https://nikolaus.net begins with accessing a DNS server to convert the host portion (nikolaus) combined with the Top Level Domain (net) of the URL into an IP address, like 203.203.25.239. Interestingly, your computer and browser include its type in all web requests, for example, Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Significance of Default Gateways
Your default gateway is usually an automatically configured address via DHCP, such as 192.0.0.37 (although they typically end in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be further routed. For IPv6, we provide an in-depth analysis on how-to-fix-ipv6-connectivity/, but you can also check on Mac or Linux with:
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 192.0.0.37 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 fe80:34f2:1639:2b32:9429%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): {37.210.104.240, 41.53.39.71}
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 b0:59:af:b5:32:7b
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 be:86:70:8b:d8:5a
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.3, 11.2.5, or 12.0.6, there are various tools available for troubleshooting. While manual actions and scripts provide some assistance, they do not offer a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) approach.
Utilizing Built-in Scripts for Assistance
One useful tool available on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although many of them are point-in-time only in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will give 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 or use Finder to point to the path. However, be mindful of the file sizes, which are typically around 300MB.
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