Fix MacOS Internet
Understanding Internet Address Allocation
When you connect to the Internet, you’re assigned a public IPv4 address like 5.122.14.147 or an IPv6 address like 2000:136f:6781:6d56:4ca3:7ece:e5de:c25. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or even referencing MAC addresses like 08:05:d0:5d:21:59 can be prone to errors and become complex. Moreover, this method does not provide any historical data, especially related to past issues.
Navigating the Internet and the Inner Workings of Lookups
Accessing a website such as https://davis.net involves initial contact with a DNS server to convert the host portion (davis) combined with the Top Level Domain (net) of the URL into an IP address like 239.215.79.173. Every web request from your computer and browser includes its specific type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Crucial Function of Default Gateways
Your default gateway is typically an automatically configured address obtained through DHCP. A default gateway such as 172.19.60.176 (often ending in .1 or .254 based on the scope size) is where your computer directs all its traffic to be routed further. For more details on configuring IPv6, see our comprehensive guide on how-to-fix-ipv6-connectivity/. You can also check 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 172.19.60.176 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 fe80:32c9:9344:cd3b:95f1%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): {53.164.170.158, 144.204.243.253}
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 08:05:d0:5d:21:59
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 c8:7a:47:bb:a8:f8
}
Fixing Connectivity Issues for Wired and Wireless Networks
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Systems
Regardless of whether you are using OSX/macOS versions such as 10.13.3, 11.3.6, or 12.2.7, there are several troubleshooting tools available. However, these tools do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that practice remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts and Commands
A helpful tool for 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. Another comprehensive tool is the sysdiagnose, which can generate a wide range of logs related to wireless, although they are mostly point-in-time.
Running the command sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, but note that it will give a privacy warning. The file sizes can be around 300MB.
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