How Can I Troubleshoot Apple Internet Connection
Understanding How Internet Addresses Function
When using the Internet, you are assigned a Public IPv4 address, such as 14.90.132.148, or an IPv6 address, such as 2000:a3f1:5093:73c9:f514:9bee:e589:5f3. This information can be verified at https://test-ipv6.com/, but explaining or communicating these addresses to non-technical individuals, as well as referring to MAC addresses like 36:04:52:9c:15:6a, can be prone to errors and become complex. Furthermore, it does not provide any historical data, particularly when addressing previous issues.
Navigating the Online Environment
To access a webpage, such as https://kozey-heathcote.co, the initial step involves contacting a DNS server to convert the host portion (kozey-heathcote) in combination with the Top Level Domain (co) of the URL into an IP address, like 226.249.247.233. Whenever web requests are made, your computer and browser consistently submit their type, as seen in the example:Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Significance of Pre-Set Gateways
The default gateway is typically an address automatically configured via DHCP. This is the location where your computer forwards all of its traffic and is commonly found ending in .1 or .254, depending on the scope size, like 192.0.0.50. For an in-depth explanation on IPv6, refer to how-to-fix-ipv6-connectivity/, or perform a check on Mac or Linux using the following method:
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 192.0.0.50 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:f4b4:a5be:799b:8b10%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): {209.83.83.35, 102.43.8.165}
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 36:04:52:9c:15:6a
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 61:d8:9e:9d:72:02
}
Fixing Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you’re using OSX or macOS version 10.15.9, 11.0.2, or 12.2.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. Automated remote troubleshooting becomes particularly valuable for teams embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A useful tool on 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 be used to generate various logs, although much of it is only related to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. To run it interactively, you can use sudo /usr/bin/sysdiagnose, which will provide 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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