How Do You Troubleshoot Mac Internet
Explanation of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 102.225.64.18 or an IPv6 address similar to 2000:a997:b5d3:204:1b1d:918:d0b2:a99c. You can verify this information at https://test-ipv6.com/. However, explaining these addresses to individuals without technical knowledge can be difficult and prone to errors. Additionally, this approach lacks historical data, especially when addressing past issues.
Navigating the World Wide Web
In order to access a website like https://borer-kshlerin.org, a DNS server is initially contacted to translate the host portion (borer-kshlerin) and the Top Level Domain (org) of the URL into an IP address, such as 132.219.245.101. Your computer and browser include its type in all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
The default gateway is typically an address that is automatically configured via DHCP. An example of a default gateway is 192.0.0.99 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed onwards. For IPv6, you can find more in-depth information about this topic in our guide on how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux by using the following command:
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 192.0.0.99 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 fe80:4ec1:7407:3c7:8a28%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): {218.65.144.211, 8.239.193.227}
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 21:19:93:5c:d2:d4
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 96:80:e0:3a:13:41
}
Resolving Connection Issues for Wired and Wireless Networks
When it comes to sending data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX
Irrespective of whether you are using OSX/macOS versions like 10.12.1, 11.5.5, or 12.2.8, there is a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI, and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool offers a more comprehensive set of logs, although most of the information is only relevant to a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in the /var/tmp/<blah>.tar.gz directory. If you prefer to run it interactively (even though there is minimal interaction), you can use sudo /usr/bin/sysdiagnose, which 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. However, be cautious of the file sizes, which are approximately 300MB.
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