How Can I Fix MacOS Internet Connection
Understanding How Internet Addressing Functions
When using the Internet, an individual may acquire a Public IPv4 address, such as 49.230.65.33, or an IPv6 address, such as 2000:116d:1e65:3ed7:1ea2:9009:2ddc:c0f7. Verification of these addresses can be performed at https://test-ipv6.com/. However, conveying these addresses to non-technical users, and even referencing MAC addresses like ef:56:5c:66:c3:9f, can be prone to errors and becomes complex quite rapidly. Moreover, this approach does not provide any historical data, particularly related to past issues.
Navigating the Internet
When attempting to visit a web page, such as https://wiegand.name, the initial step involves reaching out to a DNS server to translate the host portion (wiegand) in conjunction with the Top Level Domain (name) of the URL to an IP address, for example, 17.1.56.154. It is pertinent to note that your computer and browser disclose their type during all web requests, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
Typically, a default gateway is an address that is automatically configured through DHCP. This may manifest as a default gateway like 172.25.96.205 (although they usually end in .1 or .254 based on the scope size), and it is the entry point where all of your computer’s traffic is directed for further routing. For IPv6, a comprehensive guide is available at how-to-fix-ipv6-connectivity/, with the ability to verify 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 172.25.96.205 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:c5b0:1232:96fa:436c%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): {191.171.206.188, 96.112.29.29}
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 ef:56:5c:66:c3:9f
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 4a:02:ee:7a:db:b1
}
Solutions for Troubleshooting Wired and Wireless Connections
When it comes to sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS versions like 10.12.6, 11.4.3, or 12.1.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that are embracing remote work and Work From Anywhere (WFA) setups.
Helpful Built-in Scripts
One useful tool in 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 logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is related to wireless settings and is only available for a specific point in time, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can enter the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be aware of the large file sizes of about 300MB.
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