How Do You Fix MacOS Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 59.173.215.18 or an IPv6 address like 2000:c12:2580:adba:20df:8917:a8c7:1b3f. To verify this, you can visit https://test-ipv6.com/. However, for those who are not technology-savvy, conveying and referencing these addresses can be prone to errors and can become complex very quickly. Additionally, this method does not provide any historical data, especially when previous issues have occurred.
Navigating the World Wide Web
When accessing a website such as https://erdman.info, your first step is to connect to a DNS server to convert the host portion (erdman) combined with the Top Level Domain (info) of the URL into an IP address, such as 196.179.72.175. In fact, your computer and browser include their types in all web requests e.g. Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically configured address through DHCP. This results in a default gateway such as 192.0.0.192 (although they usually end in .1 or .254 depending on the scope size), which is where your computer sends all its traffic to be routed onwards. For IPv6, a more detailed explanation can be found in our how-to-fix-ipv6-connectivity/, or you can verify this 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 192.0.0.192 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:b84f:e945:d570:6ce6%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): {1.164.255.72, 173.153.150.191}
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 94:9e:c3:4b:06:51
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 d8:3f:e2:0c:9f:78
}
Solutions for Addressing Connectivity Issues
When it comes to transmitting data to your router, you may encounter connectivity issues using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Methods for Troubleshooting on Apple macOS / OSX
Regardless of whether you are using OSX or macOS in version 10.11.6, 11.1.3, or 12.1.9, there are various troubleshooting tools available. However, these tools may not provide a series of correlated values over time, which is essential for remote troubleshooting, especially for teams engaged in remote work and Work From Anywhere (WFA).
Utilize Built-in Scripts for Assistance
On OSX/macOS, the sudo wdutil info tool is quite useful as it provides current wireless settings for troubleshooting purposes. Similarly, the sysdiagnose tool can generate a wide range of logs, although many of these are only relevant to the wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz directory, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively by using sudo /usr/bin/sysdiagnose with a privacy warning. When not running in the background, it will 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 around 300MB.
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