How Do You Check Mac Issues
Understanding Internet Addressing
Internet addressing involves the use of Public IPv4 and IPv6 addresses, such as 75.203.115.77 and 2000:b995:8e3c:1759:ae57:8d7e:4ec8:4330. Checking these addresses on https://test-ipv6.com/ is important. However, for those unfamiliar with technical terms, communicating or identifying these addresses, as well as MAC addresses like 8c:3c:ab:35:41:62, can be complex and error-prone. Moreover, it does not provide historical data.
Navigating the Web
When accessing a web page like https://wolff.co, the first step is to access a DNS server to translate the host portion (wolff) with the Top Level Domain (co) of the URL into an IP address like 75.174.165.188. Additionally, every web request sent from your computer and browser indicates its type, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
The Significance of Default Gateways
The default gateway is typically an automatically configured address via DHCP, like 192.0.0.202 (often ending in .1 or .254 depending upon the scope size). This is where all traffic from your computer is routed. To check on Mac or Linux, you can refer to a deep dive on 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 192.0.0.202 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:df3e:70c6:86a0:e031%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): {119.201.75.46, 133.135.225.77}
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 8c:3c:ab:35:41:62
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 4c:d5:33:bc:1d:5e
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data, whether through physical or data layers, you may be utilizing either a wired or wireless (Wi-Fi) medium to send the data to your router.
Troubleshooting on Apple’s macOS / OSX
No matter the version of OSX/macOS you are using - whether it’s 10.15.9, 11.6.1, or 12.1.8 - there are various tools available for resolving connectivity issues. However, these tools and manual actions do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes especially essential for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Useful Built-in Utilities
One particularly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many are only relevant to wireless at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there is minimal interaction), you can run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are usually around 300MB.
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