How To Support Mac Issues
Understanding the Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 102.1.159.143 or an IPv6 address like 2000:5cc4:c9eb:1a92:6084:8a69:a772:25f. These assignments can be verified by visiting https://test-ipv6.com/. However, explaining these addresses to individuals who are not technologically inclined, or even referencing MAC addresses like 8a:04:34:f2:bc:95, can be prone to errors and quickly become complex. Moreover, this approach does not offer any historical data, especially regarding previous issues.
Navigating the World Wide Web
In order to access a web page such as https://bergnaum-hamill.org, you initially connect with a DNS server to translate the host part (bergnaum-hamill) combined with the Top Level Domain (org) of the URL into an IP address like 213.162.188.155. Your computer and browser also communicate their types with all web requests, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address obtained via DHCP. You receive a default gateway such as 192.0.0.105 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic for routing. For IPv6, a detailed analysis is available at how-to-fix-ipv6-connectivity/ but it can also be checked 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 192.0.0.105 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 fe80:8389:e843:e2f5:3674%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): {224.152.122.9, 139.77.137.106}
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 8a:04:34:f2:bc:95
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 6e:b9:55:c0:4c:46
}
Resolving Issues with Wired and Wireless Connections
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.
Steps to Take for Apple macOS / OSX Troubleshooting
Regardless of whether you are running 10.12.5, 11.0.7, or 12.1.5, there are several troubleshooting tools available for macOS. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing the In-Built Scripts
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI, and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a variety of logs, though much of it is point-in-time in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run, you can use sudo /usr/bin/sysdiagnose, which will trigger 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 Cmd+Shift+G in Finder. Keep in mind that the file sizes are around 300MB.
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