How Can I Check Mac Internet Connection
Understanding the Function of Internet Addresses
When using the Internet, you will be assigned a Public IPv4 address, such as 170.61.191.223, or an IPv6 address, such as 2000:a2fa:d3a1:d973:d520:8c32:1d2f:f580. This information can be verified at https://test-ipv6.com/. However, communicating these addresses to those who are not technologically savvy can be prone to errors and become complex. Moreover, this approach lacks historical data, particularly when addressing past issues.
Navigating the World Wide Web
When attempting to access a website like https://harvey.co, your first step is to contact a DNS server to convert the host portion (harvey) in combination with the Top Level Domain (co) of the URL into an IP address, such as 156.203.26.48. Every web request from your computer and browser includes its type, such as Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
The default gateway is typically an address that is automatically configured via DHCP. This address, such as 192.168.90.204 (although it generally ends in .1 or .254 based on the scope size), is where your computer sends all of its traffic for routing. For information on IPv6, a comprehensive guide is available at how-to-fix-ipv6-connectivity/. Additionally, you can check this on Mac or Linux 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 192.168.90.204 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 fe80:5a47:e033:931a:5295%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): {190.112.251.155, 226.151.198.129}
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 e1:37:19:8a:9a:58
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 af:13:6b:d9:e6:7d
}
Resolve Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data, the physical and data layer options include using either a wired or wireless (Wi-Fi) medium to communicate with your router.
Effective Solutions for Apple macOS / OSX Users
Regardless of the version of OSX or macOS you are using, whether it’s 10.12.9, 11.3.4, or 12.2.1, there exists a variety of troubleshooting tools. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have adopted remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for Troubleshooting
A helpful tool on OSX/macOS is the sudo wdutil info, which provides a CLI dump of current wireless settings and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs related to wireless issues, although most of it is only relevant to a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and produce logs in /var/tmp/<blah>.tar.gz. To run it interactively, use sudo /usr/bin/sysdiagnose, though there is minimal interaction involved. 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 around 300MB.
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