How Do You Troubleshoot Apple Connectivity
Understanding IP Addressing
When connecting to the Internet, you are assigned a unique Public IPv4 or IPv6 address, such as 12.75.77.34 or 2000:315a:f34f:e57:5fcc:472e:bd7a:1aad. To verify this, you can visit https://test-ipv6.com/. However, communicating these addresses to non-technical individuals, or even mentioning MAC addresses like a9:da:08:6a:ee:95, can become error-prone and complex. Moreover, it does not provide any historical data, especially when addressing past issues.
Navigating Websites
When accessing a website like https://thiel.co, you first connect to a DNS server to translate the combination of the host (thiel) and the Top Level Domain (co) into an IP address, such as 96.124.233.44. Interestingly, your computer and browser disclose their type with every web request, for example: Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP, such as 192.0.0.144 (commonly ending in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be directed further. For IPv6, a comprehensive guide is available at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this 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 192.0.0.144 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:b90f:d086:b2ec:e44c%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): {161.166.227.58, 111.222.4.76}
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 a9:da:08:6a:ee:95
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 c8:27:b8:df:9a:d9
}
Resolve Issues with Wireless or Wired Connections
When transferring data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Methods for Apple macOS / OSX Systems
Regardless of whether you are running OSX/macOS versions such as 10.14.6, 11.3.8, or 12.2.8, there are various troubleshooting tools available. However, these manual actions and scripts fail to provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly beneficial, especially for teams that embrace remote work and Work From Anywhere (WFA).
Handy Built-in Scripts
A useful tool for OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings via CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate numerous logs, although many are only relevant to wireless at a specific point in time just like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not running in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. Keep in mind that the file sizes are around 300MB or slightly more.
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