How To Check OSX Internet
Understanding Internet Addressing
When using the Internet, you are assigned a unique IP address, such as 65.218.34.139 for IPv4 or 2000:659a:83cf:33c1:2d96:ea58:4668:68f7 for IPv6. You can verify your IP address at https://test-ipv6.com/. However, conveying these addresses or MAC addresses like 5e:9e:ad:c5:44:a2 can be complex and error-prone, especially for those who are not technically inclined. Furthermore, it does not provide historical data to address previous issues.
Navigating the World Wide Web
Accessing a website such as https://gusikowski-romaguera.info involves contacting a DNS server to translate the host (gusikowski-romaguera) and the Top Level Domain (info) of the URL into an IP address, such as 55.175.16.161. Additionally, your computer and browser sends its type with all web requests, for example:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
Your default gateway is typically an automatically assigned address through DHCP, such as 172.17.83.19 (often ending in .1 or .254 based on the scope size). This is the endpoint where your computer directs all its traffic to be routed further. For deep insight on IPv6, you can refer to how-to-fix-ipv6-connectivity/, or check 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 172.17.83.19 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:bae4:57bc:2c39:db6e%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): {199.144.61.212, 41.93.137.138}
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 5e:9e:ad:c5:44:a2
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 90:fa:fc:a4:1f:0e
}
Fixing Connectivity Issues
When it comes to transferring data to your router, you might encounter issues at the physical and data layer, whether you’re using a wired or wireless (Wi-Fi) medium.
Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you’re using, whether it’s 10.15.9, 11.0.5, or 12.3.7, there are various tools available for troubleshooting. However, these manual actions and scripts fail to provide a series of interconnected values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that adopt remote work and Work From Anywhere (WFA) practices.
Useful Built-in Utilities
One extremely 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. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although many of them are only relevant to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively (despite minimal interaction), use the command sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the right location, or you can navigate to /var/tmp using Cmd+Shift+G in Finder. Just be cautious of the file sizes, which are approximately 300MB.
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