How Do You DiagnOSe MacOS Internet Connection
Understanding How Internet Addresses Function
When using the Internet, you will be assigned a Public IPv4 address similar to 123.250.230.195 or an IPv6 address like 2000:5e61:d102:8480:80aa:4385:1ccb:fd3f. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not tech-savvy, conveying these addresses or even referencing MAC addresses like 98:0e:c1:58:7d:82 can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially when dealing with past issues.
Navigating the World Wide Web
In order to access a website such as https://kuhlman.biz, you first connect to a DNS server to convert the host section (kuhlman) combined with the Top Level Domain (biz) of the URL into an IP address like 232.182.120.185. Your computer and browser specifies its type with every web request, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Typically, your default gateway is automatically configured via DHCP. You receive a default gateway such as 192.0.0.2 (although they usually end in .1 or .254 depending on the scope size) and this is where your computer directs all its traffic for onward routing. For IPv6, you can refer to our comprehensive guide on how-to-fix-ipv6-connectivity/ or perform a check on Mac or Linux using:
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 192.0.0.2 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:da3a:33f6:3377:b1b5%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): {132.46.218.49, 47.255.20.17}
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 98:0e:c1:58:7d:82
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 34:6b:87:57:55:be
}
Resolve Issues with Wired and 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.
Effective Solutions for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.12.1, 11.0.5, or 12.1.9, there are various troubleshooting tools available. However, these manual methods and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA) policies.
Utilize Built-in Scripts for Assistance
One useful tool for OSX/macOS is 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 produce a wide range of logs, although much of the information is only relevant to the wireless settings at a specific point in time, similar to wdutil.
To run this tool in the background and generate logs at /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for an interactive run (although there is minimal interaction), use sudo /usr/bin/sysdiagnose, which will trigger 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 or Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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