How Can I Support OSX Internet Connection
Explanation of Internet Addressing
When using the Internet, you are assigned an address, such as 176.175.24.144 for IPv4 or 2000:b14b:8ae2:3884:85ea:e088:98fa:1958 for IPv6. These can be verified at https://test-ipv6.com/. However, conveying these addresses and MAC addresses, such as de:8e:f4:59:c8:01, to those who are not technologically savvy can be prone to errors and become complex. Moreover, this method lacks historical data, particularly when past issues have arisen.
Navigating the World Wide Web
When you want to visit a webpage, such as https://mann-robel.name, you first contact a DNS server to convert the host (mann-robel) and the Top Level Domain (name) into an IP address, like 139.217.238.36. Every time you make a web request, your computer and browser also transmit information about themselves, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Significance of the Automatic Route
By way of DHCP, your default gateway is typically automatically designated. It is usually an address such as 172.18.231.190 (typically ending in .1 or .254, depending on the scope). This is the point where your computer forwards all of its traffic. For a more detailed discussion on IPv6, refer to how-to-fix-ipv6-connectivity/. On a Mac or Linux system, you can verify this information 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 172.18.231.190 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 fe80:22a:64f5:dc44:fbc3%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): {15.165.15.255, 122.3.245.91}
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 de:8e:f4:59:c8:01
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 b7:34:8e:13:fb:9e
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take on Apple macOS / OSX
No matter which version of OSX/macOS you are using, whether it’s 10.14.4, 11.6.7, or 12.0.7, there are various troubleshooting tools available. However, these tools and manual actions do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Utilizing Included Scripts for Assistance
A very beneficial tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless related settings and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a multitude of logs, although many are point-in-time only in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, which will open Finder in the correct location or allow you to navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Keep in mind that the file sizes are approximately 300MB.
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