How Do You Support Apple Issues
A Guide to Internet Addressing
When using the Internet, you will be assigned a unique address known as a Public IPv4 address, such as 244.1.1.41, or an IPv6 address, like 2000:fc4c:a2e8:94c2:9003:424f:f5a7:364a. You can confirm your address at https://test-ipv6.com/. However, for those who are not familiar with technology, communicating these addresses or MAC addresses like 4d:f3:b7:7d:ae:be can quickly become challenging and error-prone. Moreover, this method does not provide historical data, especially for previous issues.
Navigating the World Wide Web
In order to access a website, such as https://parker-brown.com, you first need to contact a DNS server in order to translate the host portion (parker-brown) in combination with the Top Level Domain (com) of the URL to an IP address, like 131.245.62.91. Your computer and browser sends its type with every web request, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an address that is automatically configured via DHCP. You will be assigned a default gateway, such as 192.0.0.154 (with common endings of .1 or .254, depending on the scope size), to which your computer sends all its traffic to be routed onwards. A more detailed guide on IPv6 connectivity can be found at how-to-fix-ipv6-connectivity/, and you can perform checks 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 192.0.0.154 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 fe80:81d6:5a7e:8b52:eef0%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): {70.228.87.50, 176.55.58.21}
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 4d:f3:b7:7d:ae:be
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 2c:0f:d3:09:a7:f2
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layers.
Troubleshooting Strategies for Apple macOS
Regardless of the version of OSX/macOS you are using, whether it’s 10.11.8, 11.6.6, or 12.1.9, there are various tools available for troubleshooting connectivity issues. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes especially valuable, particularly for teams that support remote work and Work From Anywhere (WFA) arrangements.
Leveraging Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the command line interface. It can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive solution, as it can generate a wide range of logs (although many are related to wireless settings at a specific point in time, similar to wdutil).
To run sysdiagnose in the background and generate logs at /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (although there isn’t much interaction), you can execute sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder by pressing Cmd+Shift+G. Keep in mind that the file sizes are around 300MB, more or less.
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