How To Check Mac Internet Connection
The Function of Internet Addressing
When using the Internet, individuals may have a unique Public IPv4 address such as 238.24.224.254 or an IPv6 address like 2000:c4a:6e0e:7bd9:dfdd:a09d:8ebb:80d9. This can be verified at https://test-ipv6.com/. However, relaying and communicating these addresses, as well as MAC addresses like 1c:18:96:61:97:f1, poses challenges for non-technical individuals, and becomes complex rapidly. Furthermore, this method does not provide historical data, especially regarding past issues.
Navigating Web Content
Accessing a webpage such as https://rempel.io entails initially accessing a DNS server to convert the host portion (rempel) in conjunction with the URL’s Top Level Domain (io) into an IP address, for example, 23.165.240.47. With every web request, the computer and browser transmit its 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
Typically, the default gateway is an automatically configured address through DHCP. For example, the default gateway could be 172.28.76.225 (usually ending in .1 or .254 depending on the scope size), which serves as the location where the computer forwards all its traffic. For information on checking IPv6 connectivity on Mac or Linux, refer to our article how-to-fix-ipv6-connectivity/.
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 172.28.76.225 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:bfcf:175f:14e0:6965%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): {49.105.249.80, 223.119.207.145}
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 1c:18:96:61:97:f1
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 fc:67:f7:a3:3f:bb
}
Resolve Issues with Wired or Wireless Connections
When it comes to transferring data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.12.3, 11.4.3, or 12.3.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that have adopted remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
An extremely beneficial tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to produce a wide range of logs (although many are only point-in-time related to wireless, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write the logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (despite the limited interaction), you can executesudo /usr/bin/sysdiagnose, which will display a privacy warning. If 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. However, be cautious of the file sizes, which are typically around 300MB more or less.
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