How To Fix Mac Internet Connection
Understanding Internet Addressing
When using the internet, you are assigned a Public IPv4 or IPv6 address, such as 222.240.247.185 or 2000:a300:9c14:5708:89c6:8456:bba6:fc6d. Verifying this information can be done at https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even articulating MAC addresses like fd:e2:83:d1:b0:ef, can quickly become complex and prone to errors. Moreover, this method does not provide historical data, particularly concerning past problems.
Navigating the World Wide Web
Accessing a webpage, such as https://toy.org, begins with a DNS server translating the host portion (toy) and the Top Level Domain (org) of the URL into an IP address, such as 166.189.99.162. Furthermore, your computer and browser communicate their type with all web requests, for example, Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Default Gateways
Typically, your default gateway is an address configured automatically through DHCP, such as 10.218.218.71 (often ending in .1 or .254 based on scope size), and it is where your computer directs all of its traffic to be routed. For IPv6, detailed instructions are available at how-to-fix-ipv6-connectivity/, but it can also be verified on Mac or Linux 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 10.218.218.71 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 fe80:6de7:f20e:c798:4549%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): {185.248.18.161, 172.48.240.233}
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 fd:e2:83:d1:b0:ef
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 85:ea:fc:68:d1:50
}
Resolve Issues with Wired or Wireless Connections
In the process of sending data to your router, it is essential to troubleshoot or fix issues related to wired or wireless (Wi-Fi) connections at the physical and data layer.
Solutions for Apple macOS / OSX Problems
No matter which version of OSX/macOS you are using, whether it’s 10.13.9, 11.0.5, or 12.3.7, there are various tools available for troubleshooting. While manual actions and scripts are helpful, they do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are involved in remote work and Work From Anywhere (WFA).
Useful Built-in Tools for Troubleshooting
An important tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are point-in-time only in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive mode (although there is minimal interaction), run sudo /usr/bin/sysdiagnose and it will display 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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