How Can I Fix OSX Internet Connection
The Fundamentals of Internet Addressing
When using the Internet, you are typically assigned a Public IPv4 address like 44.145.175.247 or an IPv6 address like 2000:fa09:90f4:abeb:6702:1455:2264:a9c3. The verification of these addresses can be done at https://test-ipv6.com/. However, for those who are not technically inclined, the process of communicating or identifying MAC addresses like d5:0e:98:fa:0a:13 can quickly become confusing and prone to errors. Furthermore, this method does not provide any historical data, particularly relevant during past issues.
Navigating the World Wide Web
In order to access a webpage such as https://towne-mills.net, the first step involves connecting to a DNS server, which translates the host portion (towne-mills) combined with the Top Level Domain (net) of the URL into an IP address like 46.4.141.241. With every web request, your computer and browser also send specific types, for instance, Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically configured address via DHCP. This address, such as 192.168.12.119 (although they usually end in .1 or .254, depending on the scope size), is where your computer directs all its traffic to be routed onwards. For IPv6, you can find more detailed information on how-to-fix-ipv6-connectivity/, or you can perform a check 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 192.168.12.119 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:c8ef:c846:b6f0:86ce%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): {110.102.67.251, 12.63.91.135}
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 d5:0e:98:fa:0a:13
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 c2:d9:87:ac:f3:f7
}
Resolving Wired or Wireless Connectivity Issues
When it comes to transmitting data, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer to send the data to your router.
Troubleshooting Techniques for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.3, 11.3.5, or 12.2.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Pre-Installed Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI, and can 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 limited to the wireless settings, similar to wdutil.
The command sudo nohup /usr/bin/sysdiagnose -u & will run this tool in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose and it will provide 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 to locate the files. It’s important to note that the file sizes are approximately 300MB.
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