DiagnOSe Apple Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address like 243.130.26.172 or an IPv6 address like 2000:6d0a:7e1b:668:ee6c:1f37:dde:ad42. A quick way to check your address is through https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even mentioning MAC addresses such as be:8a:3b:44:d7:47, can be prone to errors and quickly become complex. Furthermore, this method does not provide historical data, especially when dealing with past issues.
Navigating the World Wide Web
Accessing a website like https://schneider.com begins with a connection to a DNS server, which translates the host portion (schneider) combined with the Top Level Domain (com) of the URL into an IP address such as 162.147.168.53. Every web request from your computer and browser includes its type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
The default gateway is usually assigned automatically through DHCP, resulting in an address like 10.243.51.43 (typically ending in .1 or .254 based on the scope size). This address is where your computer sends all its traffic to be routed onwards. For IPv6, you can find more information in our detailed article on how-to-fix-ipv6-connectivity/, or you can verify on Mac or Linux using the following command:
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 10.243.51.43 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 fe80:2c1b:4200:dddd:6d9c%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): {207.219.153.147, 132.136.34.131}
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 be:8a:3b:44:d7:47
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:f9:74:ce:08:52
}
Resolve Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Apple macOS / OSX Troubleshooting
Regardless of whether you are running OSX/macOS version 10.11.9, 11.5.3, or 12.1.1, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing In-Built Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only point-in-time related to wireless, similar to wdutil.
To run the sysdiagnose tool in the background, use the command sudo nohup /usr/bin/sysdiagnose -u & to write logs to /var/tmp/<blah>.tar.gz. Alternatively, you can run it interactively by using sudo /usr/bin/sysdiagnose, which will issue 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. However, be mindful of the file sizes, which can be around 300MB.
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