Check MacOS Internet Connection
Understanding the Function of Internet Addressing
When using the Internet, individuals may have a unique Public IPv4 or IPv6 address, such as 14.184.229.200 or 2000:1cf0:31e8:5d52:1fbd:d504:ca6f:7515. These can be verified through https://test-ipv6.com/. However, conveying these addresses or referring to MAC addresses like 95:be:3d:f1:27:d6 can be complex and prone to errors, especially for those who are not technology savvy. Additionally, this method does not provide any historical data, particularly relating to past issues.
Navigating the Internet
In order to access a website such as https://schmitt.name, the initial step is to contact a DNS server to convert the host portion (schmitt) along with the Top Level Domain (name) of the URL into an IP address, for example 88.225.79.207. When making web requests, your computer and browser transmit its type, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Typically, the default gateway is an automatically assigned address through DHCP, like 10.73.230.117 (usually ending in .1 or .254 depending on the scope size). This is where all traffic from your computer is directed for further routing. For those interested in IPv6, we offer an in-depth analysis in how-to-fix-ipv6-connectivity/, while Mac or Linux users can check 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 10.73.230.117 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:a998:c9d0:cb8b:a01d%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): {127.0.65.160, 140.33.180.166}
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:be:3d:f1:27:d6
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 da:6b:18:b8:54:ac
}
How to 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.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are running OSX or macOS version 10.11.9, 11.2.3, or 12.2.7, there are various tools available for troubleshooting. However, manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a CLI dump of current wireless settings and can be configured to generate specific troubleshooting logs. In addition, the sysdiagnose tool can generate a wide range of logs, although much of it is only relevant to wireless settings, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and have it write logs to /var/tmp/<blah>.tar.gz. For an interactive run (though there is limited interaction), you can use sudo /usr/bin/sysdiagnose, which will result in 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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