How Do You Support MacOS Connectivity
Understanding How Internet Addresses Function
The Internet allows for the allocation of Public IPv4 addresses (e.g. 82.171.97.84) and IPv6 addresses (e.g. 2000:2eb8:cba0:b828:3e3c:1bf1:e6c7:8b66). Verification of these addresses can be done through https://test-ipv6.com/. However, for individuals without a technical background, communicating and utilizing these addresses, in addition to calling out MAC addresses like 39:a0:2a:24:8f:2b, can quickly become convoluted and susceptible to errors. Moreover, this approach does not provide any historical data, particularly regarding past issues.
The Process of Navigating the World Wide Web
When attempting to access a website such as https://schumm.com, the first step involves connecting to a DNS server in order to translate the host portion (schumm) in conjunction with the Top Level Domain (com) of the URL into an IP address such as 26.75.238.255. Each web request originating from your computer and browser includes information about its type, for example:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
The Significance of Default Gateways
The default gateway is typically an automatically configured address obtained through DHCP, such as 192.0.0.108 (although they usually end in .1 or .254 depending on the scope size). This address is where your computer directs all of its traffic to be routed onwards. For a more in-depth exploration of default gateways for IPv6, visit how-to-fix-ipv6-connectivity/. Additionally, users can verify this on Mac or Linux systems by:
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 192.0.0.108 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:f511:7608:8c65:ac90%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): {223.68.0.40, 31.55.1.22}
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 39:a0:2a:24:8f:2b
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 37:93:7c:16:3a:8a
}
Tips for Resolving Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Actions to Take on Apple macOS / OSX
No matter which version of OSX/macOS you are currently running, whether it’s 10.11.1, 11.5.5, or 12.3.6, 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 beneficial, especially for teams that embrace remote work and Work From Anywhere (WFA).
Default Scripts That Might Be Useful
A very useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface, and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are only relevant to wireless settings, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, you can execute it in the background and it will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there is not much interaction), you can run 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 or use Finder with Cmd+Shift+G to navigate to the path. Just keep in mind that the file sizes will be approximately 300MB.
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