Fix OSX Internet
Internet Protocol Addressing: A Simplified Explanation
When using the Internet, you will be assigned a Public IPv4 address, such as 81.202.119.142, or an IPv6 address like 2000:1722:e545:f678:d702:d12d:13b9:57a5. Verifying this information can be done through this website. However, conveying these addresses to individuals who are not technology-savvy, or even referencing MAC addresses such as 49:fe:fe:ba:b3:d2, can be prone to errors and becomes complex quickly. Furthermore, this method does not provide any historical data, especially when trying to address previous issues.
Navigating the World Wide Web
Accessing a web page, such as https://roob.org, initially involves connecting to a DNS server to convert the host portion (roob) combined with the Top Level Domain (org) of the URL to an IP address, such as 94.208.251.143. When making web requests, your computer and browser transmit their type, for example Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Default Gateways
By default, your gateway is usually an automatically configured address through DHCP. You receive a default gateway, such as 172.21.22.2 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be routed further. To check on Mac or Linux, you can delve deeper into the topic of IPv6 connectivity by visiting this guide.
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 172.21.22.2 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 fe80:9a2:17aa:a150:8a77%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): {223.210.31.115, 163.68.130.198}
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 49:fe:fe:ba:b3:d2
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 88:c7:47:79:f4:24
}
How to Resolve Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.12.9, 11.0.5, or 12.0.2, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are adopting remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts for Troubleshooting
A highly useful tool for OSX/macOS users is sudo wdutil info, which provides a dump of current wireless settings to the CLI, and can also generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range 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, you can use the 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 generate a privacy warning. 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 approximately 300MB.
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