How Can I DiagnOSe Apple Connectivity
Understanding IP Addressing
When using the Internet, individuals may be provided with a Public IPv4 address such as 246.12.193.255 or an IPv6 address like 2000:afea:c082:b126:2097:2b74:e1c5:ffde. These addresses can be verified by visiting https://test-ipv6.com/. However, conveying these addresses to those who are not tech-savvy, or even referencing MAC addresses like 82:5f:aa:b8:c4:67, can quickly become prone to errors and complex. Moreover, there is no historical data available, particularly for past issues.
Navigating the Internet
When attempting to reach a webpage, such as https://ruecker.biz, the first step involves accessing a DNS server to convert the URL’s host portion (ruecker) combined with its Top Level Domain (biz) into an IP address, such as 154.227.43.55. Additionally, computers and browsers send their type with every web request, 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
The Significance of Default Gateways
By default, a gateway is usually automatically configured through DHCP. This gateway, such as 10.196.236.92 (typically ending in .1 or .254 based on the scope size), is where a computer directs all of its traffic to be routed. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/, or it can be verified on Mac or Linux using:
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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 10.196.236.92 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:a03b:5544:88c0:58c7%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): {94.33.216.193, 125.17.148.24}
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 82:5f:aa:b8:c4:67
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 36:88:64:45:a7:a6
}
Resolving Issues with Wired and 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 Addressing Problems on Apple macOS / OSX
Regardless of whether you are running OSX/macOS version 10.11.1, 11.5.7, or 12.2.4, 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 invaluable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Utilizing Pre-Installed Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI. This tool can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive range of logs, although much of it is relevant to wireless issues only, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose, which will trigger 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 around 300MB, give or take.
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