How To Test OSX Internet Connection
The Functioning of Internet Addressing
When using the Internet, individuals may receive different types of IP addresses. These can include a Public IPv4 address such as 61.238.30.153 or an IPv6 address like 2000:a5df:a12:224d:4783:9e8:418d:7a7c. The verification of these addresses can be checked at https://test-ipv6.com/. This process can be challenging for non-technical individuals and may lead to errors when trying to communicate or recall these addresses, or even when dealing with MAC addresses like 23:71:6a:07:40:e1. Furthermore, this method is not suitable for accessing historical data, especially in the case of past problems.
Navigating the Internet
When attempting to reach a website such as https://hane-okon.org, the initial step involves accessing a DNS server to convert the host section (hane-okon) combined with the Top Level Domain (org) of the URL into an IP address, for instance 67.95.119.214. With every web request, your computer and browser transmit their type, as evidenced by Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway typically receives an automatically administered address through DHCP. This address, such as 172.20.162.244 (although they typically end in .1 or .254 depending on the scope size), is where a computer directs all its traffic to be routed further. For information on how to address IPv6 connectivity issues, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, the status of default gateways can be verified 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 172.20.162.244 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 fe80:3a2e:e2cc:95c6:27fb%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): {106.142.222.185, 81.180.128.170}
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 23:71:6a:07:40:e1
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 3c:1c:f0:59:33:9b
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may choose to use either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Systems
Regardless of which version of OSX/macOS you are running - be it 10.15.2, 11.3.1, or 12.1.5 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, making it essential to consider the benefits of automated remote troubleshooting, particularly for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Effective Built-in Scripts
One extremely useful tool on OSX/macOS is sudo wdutil info, which provides a comprehensive dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be used to produce a wide range of logs, although most of the information is only relevant at a specific point in time, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz, or to run it interactively, you can utilize sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to note that the file sizes can reach approximately 300MB.
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