How Can I DiagnOSe MacOS Internet
Functioning of Internet Addressing
When using the Internet, you might be assigned a Public IPv4 address such as 179.143.154.192 or an IPv6 address like 2000:7d07:d95f:95f:a74e:4a93:549d:4e4e. The verification for this can be done on https://test-ipv6.com/. However, for individuals who are not well-versed in technology, attempting to communicate these addresses, and even referring to MAC addresses like bf:c8:1a:30:b8:99, can be prone to errors and can become complex quickly. Furthermore, this method does not provide any historical information, particularly when past issues have arisen.
Navigating the Internet
In order to visit a website such as https://zieme.name, the first step is to access a DNS server to convert the host portion (zieme) along with the Top Level Domain (name) of the URL, into an IP address like 141.164.132.209. Interestingly, with every web request, your computer and browser actually transmit its type, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
Typically, your default gateway is an address that is configured automatically through DHCP. You are assigned a default gateway, such as 172.27.71.45 (usually ending in .1 or .254 depending on the size of the scope), and this is the location your computer forwards all its traffic to be routed further. For detailed information about IPv6, you can refer to our in-depth analysis on how-to-fix-ipv6-connectivity/. It is also possible to check this on Mac and Linux using the following method:
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 172.27.71.45 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:ec76:9882:7d5:c926%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): {53.157.60.175, 147.56.95.243}
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 bf:c8:1a:30:b8:99
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 c5:3b:91:26:8a:e0
}
Resolve Issues with Wired and Wireless Connections
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
No matter which version of OSX/macOS you are running - whether it’s 10.12.6, 11.6.3, or 12.3.6, there are various tools available for addressing connectivity issues. However, these manual interventions and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting shines, especially for teams that are adopting remote work and Work From Anywhere (WFA) practices.
Utilize the Built-in Scripts for Assistance
A very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the command line interface (CLI) and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although most of them are only relevant at a specific point in time in relation to wireless connectivity, similar to the wdutil tool.
By running sudo nohup /usr/bin/sysdiagnose -u &, it will run in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there isn’t much interaction), you can execute the command 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. Keep in mind that the file sizes are approximately 300MB.
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