How Can I Support OSX Issues
Understanding the Functioning of Internet Addresses
When using the Internet, individuals may receive a Public IPv4 address, such as 47.69.69.137, or an IPv6 address, like 2000:5b80:bd21:bd5:297b:90d3:512e:d6ef. Verification can be done at https://test-ipv6.com/. However, conveying these addresses to those not well-versed in technology, and even mentioning MAC addresses like da:0e:b2:50:9f:2a, can lead to errors and complexities. Furthermore, this method does not provide historical data, particularly from past issues.
Navigating the Internet
To access a website, such as https://gusikowski.name, one must initially connect to a DNS server in order to convert the host section (gusikowski) combined with the Top Level Domain (name) of the URL to an IP address, such as 35.221.29.31. With each web request, the system and browser essentially transmits its type, like Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
The default gateway is usually an address configured automatically via DHCP. A typical default gateway, such as 10.203.195.19 (usually ending in .1 or .254 depending on the scope size), is where a computer forwards all its traffic for routing. Specifically for IPv6, there is an elaborate outline available at how-to-fix-ipv6-connectivity/. On Mac or Linux, the verification process can be performed 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 10.203.195.19 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 fe80:8be3:4416:a6dc:f984%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): {107.223.114.240, 84.106.88.130}
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 da:0e:b2:50:9f:2a
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 c7:be:9a:a8:99:c2
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Techniques for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using - whether it’s 10.12.9, 11.0.3, or 12.2.8 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, which is where the importance of automated remote troubleshooting becomes evident, especially for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts for Assistance
One valuable 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 logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, if you want to run it interactively, you can execute sudo /usr/bin/sysdiagnose and it will prompt 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. Keep in mind that the file sizes are approximately 300MB.
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