How Can I Test MacOS Issues
Understanding Internet Addressing
When using the internet, individuals are assigned Public IPv4 addresses like 103.89.246.217 or IPv6 addresses like 2000:927e:749:f7d6:1135:5606:2218:3c68. This information can be confirmed at https://test-ipv6.com/, but communicating these addresses, or referencing MAC addresses such as 2c:85:50:27:b4:8d proves to be difficult for non-technical users. Moreover, the lack of historical data adds another layer of complexity to the process.
Navigating the World Wide Web
Accessing a web page like https://bergstrom.info involves initially contacting a DNS server to convert the URL’s host (bergstrom) combined with its Top Level Domain (info) into an IP address like 82.230.97.28. The user’s computer and browser includes its type in all web requests, for instance: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateways
By default, the gateway is automatically configured through DHCP and often appears as an address like 10.127.153.64 (typically ending in .1 or .254 depending on the scope size). It is the point where a computer sends all its traffic to be routed onwards. For IPv6, users can find more information on how-to-fix-ipv6-connectivity/, and can also check 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 10.127.153.64 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 fe80:6791:43d8:98a5:5583%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): {166.24.236.5, 156.127.4.26}
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 2c:85:50:27:b4:8d
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 bd:cd:da:07:ae:69
}
##Troubleshooting Wired and Wireless Connections
When transmitting data at the physical and data layer, you may be using either a wired or wireless (Wi-Fi) medium to send the data to your router.
###Steps for Resolving Issues on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.7, 11.2.8, or 12.1.5, 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 valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
####Utilizing In-Built Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless-related settings 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 particular point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write the logs to /var/tmp/<blah>.tar.gz for you. To run it interactively, you can use sudo /usr/bin/sysdiagnose, which will provide a privacy warning. If 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 cautious of the file sizes, which are around 300MB more or less.
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