How Do You Troubleshoot MacOS Issues
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address, such as 46.214.78.155, or an IPv6 address, like 2000:f27:93a:faf1:bd8a:9511:f0a:cec4. You can verify this information by visiting https://test-ipv6.com/. However, attempting to communicate these addresses or MAC addresses, like 8d:75:e6:8b:4a:7f, can be error-prone and complicated for non-technical individuals. Moreover, this information lacks historical data from previous issues.
Accessing Websites
To access a web page, such as https://smith.com, your computer first contacts a DNS server to translate the host portion (smith) and the Top Level Domain (com) of the URL into an IP address, like 232.132.64.203. Along with every web request, your computer and browser send its type, 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 Default Gateways
Typically, your default gateway is an automatically configured address assigned via DHCP, such as 172.16.158.196 (usually ending in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be routed onwards. For IPv6 issues, there is an in-depth guide available at how-to-fix-ipv6-connectivity/. In Mac or Linux, you can check this with:
<br>
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 172.16.158.196 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:cabd:b808:f20a:767e%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): {74.77.17.71, 41.109.147.178}
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 8d:75:e6:8b:4a:7f
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 19:53:d7:a2:e7:18
}
Solutions for Resolving Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Options for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.15.7, 11.3.1, or 12.1.6, there is a variety of troubleshooting tools available. 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 embrace remote work and Work From Anywhere (WFA).
Useful Built-in Tools
On OSX/macOS, a very useful tool is 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 comprehensive tool is sysdiagnose, which can generate a wide range of logs related to wireless (though most are only point-in-time logs, similar to wdutil).
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be cautious of the large file sizes (about 300MB or more).
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
