How Can I Troubleshoot MacOS Issues
Understanding Internet Addressing
When connecting to the Internet, you are assigned a public IPv4 address such as 182.13.90.77 or an IPv6 address like 2000:99:5412:29b4:b867:2bb4:9b2a:c541. Verifying this information can be done through the Test IPv6 website. However, conveying these addresses, along with MAC addresses like 7a:eb:75:2a:2b:d7, to non-technical individuals can be error-prone and complex. Additionally, it does not provide historical data of previous issues.
Navigating the World Wide Web
When accessing a website such as https://leffler.biz, your computer initially communicates with a DNS server to convert the host portion (leffler) along with the Top Level Domain (biz) of the URL into an IP address like 245.242.171.46. Your computer and browser include its type in all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. This default gateway, such as 10.219.100.44 (usually ending in .1 or .254 depending on the scope size), is where your computer sends all of its traffic to be routed. For IPv6 connectivity troubleshooting on Mac or Linux, in-depth information is available at how-to-fix-ipv6-connectivity/.
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 10.219.100.44 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 fe80:3805:662:1572:5fe6%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): {228.192.99.230, 29.249.125.177}
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 7a:eb:75:2a:2b:d7
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 98:92:66:ac:69:31
}
Solve Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Connectivity Problems on Apple macOS / OSX
Regardless of the version of OSX/macOS you have - whether it’s 10.14.1, 11.6.6, or 12.2.1 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams that are adopting remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI 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 much of it is only relevant at a specific point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there is minimal interaction), you can usesudo /usr/bin/sysdiagnose, which will provide 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. Just be mindful of the file sizes, which 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 🏠🏝🛰.
