How To Support Mac Internet
Understanding Internet Addressing Systems
When using the Internet, individuals may receive a Public IPv4 address such as 77.145.163.19 or an IPv6 address such as 2000:5767:feef:8dd6:35fb:fa59:a940:6c01. Verification of this information can be done through https://test-ipv6.com/. Nevertheless, the task of conveying these addresses to non-technical personnel, or even referencing MAC addresses like 95:49:20:69:0e:cf, can lead to errors and a rapid increase in complexity. Moreover, this does not provide any historical data, especially in relation to past issues.
Navigating the World Wide Web
Accessing a web page such as https://glover-sawayn.net initially involves contacting a DNS server to convert the host part (glover-sawayn) combined with the Top Level Domain (net) of the URL to an IP address, for example, 165.248.241.2. During all web requests, your computer and browser transmit their type, such as: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
The Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP. An example of a default gateway is 192.0.0.213 (although they generally end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, a detailed guide can be found at how-to-fix-ipv6-connectivity/, or it can be checked on Mac or Linux using the following command:
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 192.0.0.213 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 fe80:60a5:752e:a31a:2192%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): {115.34.17.12, 60.13.81.220}
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 95:49:20:69:0e:cf
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 60:66:04:69:bb:f4
}
Resolving Connectivity Issues for Wired and Wireless Networks
When transferring data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.11.2, 11.1.7, or 12.2.7, there are various tools available for resolving connectivity issues. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Pre-installed Scripts for Assistance
An extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless-related settings to the CLI and can also be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool offers a more comprehensive solution, generating a wide range of logs (although much of this is only relevant to wireless at a specific point in time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, if you prefer to run it interactively (even though there is minimal interaction), you can execute sudo /usr/bin/sysdiagnose, which will trigger a privacy warning. If not run in the background, it should open Finder in the correct location, and you can navigate to /var/tmp or use Finder with Cmd+Shift+G to specify the path. Keep in mind that the file sizes are approximately 300MB.
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