How Do You Fix OSX Internet Connection
Demystifying Internet Addressing
When connecting to the Internet, you are assigned a unique address, such as 249.169.248.169 for IPv4 or 2000:ceb0:bd9c:832b:d2c0:5feb:da2f:2ce3 for IPv6. To verify this, you can visit https://test-ipv6.com/. However, sharing or communicating these addresses, and even mentioning MAC addresses like 60:0f:e0:38:8b:7c, can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially from previous issues.
Navigating the World Wide Web
To access a website, such as https://auer.net, your computer first consults a DNS server to translate the host name (auer) and the Top Level Domain (net) of the URL into an IP address, such as 176.28.180.12. In fact, your computer and browser communicate their types with every web request, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding the Significance of Default Gateways
Your default gateway is typically a DHCP-configured address. It usually ends with .1 or .254, depending on the scope size, such as 192.0.0.254. This is where your computer directs all its traffic to be routed onward. For IPv6, you can find in-depth details on how-to-fix-ipv6-connectivity/, but you can also 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 192.0.0.254 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 a47c:242e:c3:446e:4411:a20d:b2db:f3a%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): {93.65.53.168, 234.189.106.201}
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 60:0f:e0:38:8b:7c
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 7f:92:66:b5:35:d5
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions such as 10.11.7, 11.0.6, or 12.2.7, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a consistent set of correlated values over time. This is where automated remote troubleshooting becomes particularly valuable, especially for teams that are fully embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Another comprehensive tool is the sysdiagnose, which can generate a wide range of logs (though much of it is only related to wireless settings at a specific point in time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there is minimal interaction), you can use sudo /usr/bin/sysdiagnose, which will trigger 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 mindful of the file sizes, which are typically around 300MB.
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