How To Support MacOS Connectivity
Understanding the Functionality of Internet Addresses
In the realm of the Internet, individuals are assigned either a Public IPv4 address, such as 48.252.46.9, or an IPv6 address like 2000:21a6:6c1b:4b1d:f4f7:f15a:2a:98df. These can be verified through https://test-ipv6.com/. However, relaying these addresses to those unfamiliar with the technical aspects, or even mentioning MAC addresses like b7:a4:80:84:18:59, can easily lead to errors and confusion. Moreover, this method does not offer any historical data, especially regarding past issues.
Navigating Web Content
When attempting to access a website, such as https://armstrong.org, one must initially contact a DNS server to convert the host portion (armstrong) combined with the Top Level Domain (org) of the URL, into an IP address like 146.230.196.103. Furthermore, the computer and browser provide its specifications with all web requests, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Pre-Set Gateways
Ordinarily, an individual’s default gateway is automatically configured via DHCP, resulting in the assignment of an address such as 172.19.51.198 (typically ending in .1 or .254 based on the scope size). This gateway is utilized to direct all computer traffic onwards. For IPv6, a detailed analysis can be found at how-to-fix-ipv6-connectivity/, or confirmed on Mac or Linux using the following command:
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 172.19.51.198 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:a512:3c8e:a60:bc66%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): {74.91.19.40, 229.3.188.111}
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 b7:a4:80:84:18:59
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 30:25:19:82:77:f9
}
Fixing Connectivity Issues for Wired or Wireless Networks
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Problems
Regardless of whether you are using OSX/macOS versions such as 10.15.8, 11.5.8, or 12.2.6, there are various troubleshooting tools available. However, these manual tools and scripts do not provide a series of correlated values over time, making automated remote troubleshooting essential, especially for teams practicing remote work and Work From Anywhere (WFA).
Embedded Scripts for Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Another more comprehensive tool is the sysdiagnose, which can be used to generate a wide range of logs related to wireless issues. Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, you can run sudo /usr/bin/sysdiagnose interactively, which will give a privacy warning and open Finder in the correct location. However, be mindful of the file sizes, which can be around 300MB.
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