Fix Mac Internet Connection
Understanding the Basics of Internet Addressing
When using the Internet, you are assigned a unique identifier in the form of a Public IPv4 address, such as 129.8.31.94, or an IPv6 address like 2000:b4a2:9bc1:7b27:8efd:f39d:93c9:b240. Verifying these addresses can be done at https://test-ipv6.com/, but for those who are not well-versed in technology, communicating or identifying these addresses can be challenging and error-prone. Furthermore, this method does not provide historical data, which can be crucial for addressing past issues.
Navigating Online Platforms
Accessing a website, such as https://cruickshank.co, involves using a DNS server to convert the URL’s host portion (cruickshank) and the Top Level Domain (co) into an IP address, like 181.245.160.3. Additionally, your computer and web browser send specific details with any web requests, such as <br>Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Exploring the Significance of Default Gateways
The default gateway, typically automatically configured through DHCP, plays a crucial role in routing your computer’s traffic. This gateway, represented by an address like 172.31.2.93 (usually ending in .1 or .254 based on the scope size), is where all outgoing traffic is directed. For troubleshooting IPv6 connectivity on Mac or Linux, refer to our in-depth guide at how-to-fix-ipv6-connectivity/.
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 172.31.2.93 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 fe80:1d27:8b5e:8c2c:f436%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): {13.4.140.66, 233.36.159.44}
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 8c:19:25:8c:f3:d7
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 7c:7d:f2:8f:3d:fa
}
Solutions for Resolving Connectivity Issues with Wired and Wireless Networks
When it comes to transmitting data to your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.13.1, 11.5.5, or 12.1.3, there are various tools available for troubleshooting. However, simply relying on these tools and manual actions may not provide you with a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams engaged in remote work and Work From Anywhere (WFA) arrangements.
Useful Built-in Scripts for Troubleshooting
On OSX/macOS, the sudo wdutil info tool is quite useful as it provides a dump of the current wireless settings to the command line interface, and it can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although many of these are only relevant at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and have it write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will trigger a privacy warning and open Finder in the correct location. Alternatively, you can navigate to the /var/tmp location using Finder with Cmd+Shift+G, but be mindful of the file sizes, which are usually around 300MB.
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