Check MacOS Connectivity
The Functioning of Internet Addressing
When using the Internet, you receive a Public IPv4 address such as 125.238.87.119 or an IPv6 address like 2000:46ca:4312:2550:33fc:b27f:5994:a5c8. Verification of this can be done at https://test-ipv6.com/. However, trying to communicate these addresses, or referring to MAC addresses like 38:8e:7e:9c:cd:2c, can be prone to errors and quickly becomes complex, especially for those without a technical background. Moreover, this method does not provide historical data, particularly from previous issues.
Navigating the World Wide Web
In order to access a web page like https://stiedemann-gulgowski.io, you first connect to a DNS server to convert the host portion (stiedemann-gulgowski) combined with the Top Level Domain (io) of the URL into an IP address like 50.159.176.182. With every web request, your computer and browser actually send its type as well, for example Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. The default gateway, such as 192.168.109.242 (usually ending in .1 or .254 depending on the scope size), is where your computer routes all its traffic. For IPv6, you can find more detailed information on how-to-fix-ipv6-connectivity/ or check 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 192.168.109.242 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 fe80:8930:5f94:c9f2:d803%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): {188.196.81.28, 120.92.237.32}
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 38:8e:7e:9c:cd:2c
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 25:d5:f9:2a:b6:b5
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transferring data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.14.5, 11.3.5, or 12.1.9, there are various troubleshooting tools available. However, these manual interventions and scripts do not provide a set of interconnected values over a period of time. This is where automated remote troubleshooting becomes valuable, particularly for teams operating remotely and embracing the concept of Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
An efficient tool for users of 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 purposes. Additionally, the sysdiagnose tool offers a more comprehensive approach, allowing users to generate a wide range of logs, although most are related to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, users can enter the command sudo nohup /usr/bin/sysdiagnose -u &. If users prefer to run it interactively, they can use the command sudo /usr/bin/sysdiagnose and heed the privacy warning. When not run in the background, this command should open Finder in the correct location, or users can navigate to /var/tmp manually or through Finder using Cmd+Shift+G to locate the path. It is important to note that the file sizes will be approximately 300MB.
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