How Do You Check OSX Issues
The Functioning of Internet Addressing
When using the Internet, you might receive a Public IPv4 address such as 185.242.6.226 or an IPv6 address like 2000:3fa:ed11:cd1a:3bb5:650d:b6d2:2f63. Verification can be done through https://test-ipv6.com/. However, conveying these addresses to non-technical individuals or dealing with MAC addresses like 02:43:64:bd:9e:13 can be prone to errors and quickly become complex. Moreover, this method lacks historical data, specifically during past issues.
Navigating the Internet
When visiting a web page such as https://kautzer.com, the first step involves accessing a DNS server to convert the host portion (kautzer) combined with the Top Level Domain (com) of the URL into an IP address like 25.186.158.185. Additionally, your computer and browser transmit their type with all web requests, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
The Significance of Default Gateways
The default gateway is typically an automatically configured address via DHCP, such as 10.32.36.223 (although they commonly end in .1 or .254 depending on the scope size). This is where your computer sends all of its traffic to be routed onwards. For IPv6, a thorough explanation can be found in how-to-fix-ipv6-connectivity/ but you can also verify 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 10.32.36.223 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 fe80:7e47:7590:12c4:7c59%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): {22.213.26.80, 172.153.100.207}
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 02:43:64:bd:9e:13
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 92:4f:bc:f8:6d:21
}
Resolving Issues with Wired and Wireless Connections
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.
Tips for Troubleshooting on Apple macOS / OSX Systems
No matter which version of OSX/macOS you’re operating on - whether it’s 10.15.1, 11.2.4, or 12.3.9 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) approach.
Effective Built-in Tools for Assistance
One extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, though much of it is only relevant at a specific point in time in relation to wireless, similar to wdutil.
Using sudo nohup /usr/bin/sysdiagnose -u & will run the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there isn’t much interaction), you can runsudo /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 Finder with Cmd+Shift+G. However, be mindful of the file sizes, which are approximately 300MB or thereabouts.
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