How Do You DiagnOSe Apple Connectivity
Functioning of Internet Addressing
When using the Internet, individuals may have a Public IPv4 address, such as 72.111.27.232, or an IPv6 address, like 2000:e344:93df:3ca1:14f5:4fed:c54:5fce. This can be verified at https://test-ipv6.com/. However, conveying these addresses to those unfamiliar with technical jargon or referencing MAC addresses, such as 08:1a:d8:67:ac:11, can lead to errors and rapid complexities. Moreover, this method lacks historical data, particularly with past incidents.
Navigating the Internet
To access a website like https://schamberger-conroy.co, it is necessary to first connect to a DNS server, which translates the host section (schamberger-conroy) in combination with the URL’s Top Level Domain (co) into an IP address, such as 242.92.0.6. Additionally, when making web requests, the computer and browser send their type, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
Typically, the default gateway is an address configured automatically via DHCP, such as 192.0.0.80 (usually ending in .1 or .254 depending on the scope size). This is where all computer traffic is sent for further routing. For IPv6, a more detailed explanation can be found in our article how-to-fix-ipv6-connectivity/, and it is possible to check on Mac or Linux 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 192.0.0.80 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 fe80:4439:51f4:64a9:ec32%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): {161.101.97.96, 84.110.136.110}
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 08:1a:d8:67:ac:11
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 08:0d:e6:67:42:da
}
Solutions for Troubleshooting Wired and Wireless Connections
When transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips and Tricks for Apple macOS / OSX Users
Regardless of your version of OSX/macOS - whether it’s 10.14.5, 11.1.7, or 12.0.4 - there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that have adopted remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also generate specific logs for troubleshooting. 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, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose, but keep in mind that it will give a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder or with the shortcut Cmd+Shift+G. Be cautious of the file sizes, which are typically around 300MB.
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