How Do You DiagnOSe MacOS Issues
The Functioning of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 57.210.169.45 or an IPv6 address like 2000:6ba0:1902:365d:75cf:c35d:d77:96e. You can verify this information at https://test-ipv6.com/. However, attempting to communicate these addresses, or even mentioning MAC addresses like 00:e7:f8:cf:d3:89, can be error-prone and quickly become complex, especially for individuals without technical expertise. In addition, this method does not provide historical data, particularly during past incidents.
Navigating the World Wide Web
When trying to access a website, such as https://lemke.org, you first connect to a DNS server to convert the host part (lemke) along with the Top Level Domain (org) of the URL into an IP address, such as 219.131.80.206. Furthermore, your computer and browser transmit its type with each web request, 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 automatically configured through DHCP and may appear as a default gateway like 172.25.52.120 (although they usually end in .1 or .254, depending on the scope size). This is the point to which your computer forwards all its traffic to be routed further. For IPv6, we provide an in-depth exploration in our post how-to-fix-ipv6-connectivity/, and you can verify 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 172.25.52.120 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 fe80:8c06:b50a:26a:8b14%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): {40.197.55.24, 199.165.105.168}
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 00:e7:f8:cf:d3:89
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 32:72:6f:08:53:8d
}
Solutions for Resolving Connectivity Issues in Wired and Wireless Networks
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.
Resolving Connectivity Problems on Apple macOS / OSX
No matter which version of OSX/macOS you are running, whether it’s 10.14.5, 11.0.3, or 12.3.8, there are various troubleshooting tools available. However, these manual actions and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting proves to be extremely beneficial, particularly for teams that are transitioning to remote work and the Work From Anywhere (WFA) concept.
Effective Built-in Scripts
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, for a more comprehensive approach, the sysdiagnose tool can be used to generate a wide range of logs, although many are only relevant to the wireless connection, similar to wdutil.
To run the sysdiagnose tool in the background and save the logs to /var/tmp/<blah>.tar.gz, 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, 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 direct Finder to the path. Keep in mind that the file sizes are approximately 300MB.
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 🏠🏝🛰.
