How Do You Understand Apple Issues
Understanding Internet Address Allocation
When using the internet, you are assigned a Public IPv4 address, such as 46.75.84.83, or an IPv6 address like 2000:c334:2c34:4c92:76ec:f464:1428:21a. Confirm this information by visiting https://test-ipv6.com/. However, conveying these addresses to individuals without technical knowledge can be complicated and error-prone, and it does not provide any historical data.
Navigating the World Wide Web
Accessing a webpage like https://blick.org involves an initial connection to a DNS server to convert the host part (blick) and Top Level Domain (org) of the URL into an IP address, such as 181.213.64.58. When making web requests, your computer and browser send specific information, such as 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 Gateway Configuration
Your default gateway is typically assigned automatically through DHCP and is commonly in the form of 10.16.159.154 (although it usually ends in .1 or .254 depending on the scope). This address is where your computer forwards all its traffic. For IPv6, you can find detailed instructions on how-to-fix-ipv6-connectivity/ or check on Mac or Linux by 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 10.16.159.154 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:b9a9:4e81:daed:3218%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): {84.196.108.64, 0.162.177.20}
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 e9:19:d2:d5:f3:b8
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 5c:bb:ed:61:0d:51
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX or macOS version 10.14.2, 11.0.1, or 12.1.2, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time, making automated remote troubleshooting an essential option, particularly for teams working remotely or adopting Work From Anywhere (WFA) practices.
Useful Built-in Scripts
A very beneficial tool for OSX/macOS is sudo wdutil info, which provides a comprehensive dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can generate a wide range of logs, although many of them are only relevant to wireless settings at a specific point in time, similar to wdutil.
To run it in the background and create logs in /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (despite minimal interaction), use sudo /usr/bin/sysdiagnose, but be prepared for large file sizes of around 300MB.
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