How Do You DiagnOSe Apple Internet
Understanding Internet Addressing
When using the Internet, you may have a Public IPv4 address such as 172.49.135.125 or an IPv6 address like 2000:9cf0:8ec3:75b1:218f:9b59:a1fd:6df6. This information can be verified at https://test-ipv6.com/. However, for individuals who are not technically inclined, conveying these addresses, or even referencing MAC addresses like fc:fd:b6:7b:25:b7, can be prone to error and can become complex very quickly. Additionally, this approach does not provide any historical data, particularly when dealing with past issues.
Navigating the World Wide Web
When accessing a web page, such as https://williamson-west.co, the first step is to access a DNS server to convert the host portion (williamson-west) along with the Top Level Domain (co) of the URL into an IP address, like 76.197.123.222. Your computer and browser includes its type in all web requests, for example:
<br>Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. You receive a default gateway, such as 192.168.199.218 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onward. For IPv6, a detailed explanation can be found at how-to-fix-ipv6-connectivity/, but it can also be checked on Mac or Linux using:
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 192.168.199.218 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:f404:7c46:c076:6331%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): {175.243.234.254, 185.105.14.41}
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 fc:fd:b6:7b:25:b7
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 84:94:54:22:6f:e9
}
Solutions for Wired or Wireless Connectivity Issues
When it comes to sending data to your router, you may encounter connectivity issues at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Strategies for Resolving Issues on Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions such as 10.11.2, 11.2.4, or 12.3.5, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a continuous set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and the Work From Anywhere (WFA) approach.
Utilizing Built-in Scripts for Troubleshooting
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI, and can be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive range of logs, although much of the information is specific to a point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in the /var/tmp/<blah>.tar.gz directory. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose and it will display a privacy warning. When run in the foreground, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to note that the file sizes are approximately 300MB.
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