How To Fix OSX Internet
Understanding Internet Addresses
When using the Internet, you are assigned an address such as 247.251.175.255 for IPv4 or 2000:21ff:fef3:ecff:8812:5e46:5528:548a for IPv6. These addresses can be verified at https://test-ipv6.com/. However, conveying these addresses to individuals not well-versed in technology, or even mentioning MAC addresses like 37:24:81:8f:98:8c, can be prone to errors and quickly become complicated. Furthermore, this method does not provide any historical data, especially in cases of past issues.
Navigating the World Wide Web
Accessing a website such as https://christiansen.org involves the initial contact with a DNS server to convert the host part (christiansen) and the Top Level Domain (org) of the URL into an IP address, such as 210.97.76.191. Your computer and browser also convey their types in all web requests, for example:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding Default Gateways
A default gateway is typically an address automatically configured via DHCP, such as 192.0.0.64 (usually ending in .1 or .254 based on the scope size), where your computer routes all of its traffic. For IPv6, you can refer to our in-depth explanation at how-to-fix-ipv6-connectivity/ or use the following commands on Mac or Linux:
<br>
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 192.0.0.64 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 fe80:5ff7:f8e9:c3f5:7047%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): {133.231.157.29, 73.117.198.8}
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 37:24:81:8f:98:8c
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 16:25:7c:0b:41:81
}
How to Troubleshoot and Fix Connectivity Issues
When it comes to transmitting data to your router, you may encounter problems at the physical and data layer, whether you’re using a wired or wireless (Wi-Fi) medium.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX or macOS you’re running, be it 10.13.4, 11.4.2, or 12.3.2, there are various tools available for troubleshooting. However, the manual actions and scripts fall short of providing a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts for Troubleshooting
One particularly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. In addition, the sysdiagnose tool can be used to generate a comprehensive set of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the following command: sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will display a privacy warning and open Finder in the correct location. Alternatively, you can navigate to /var/tmp using Finder with Cmd+Shift+G or use Finder to locate the path. Keep in mind that the file sizes are approximately 300MB.
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