How Can I Support OSX Connectivity
Understanding Internet Protocol Addressing
When using the Internet, an individual may be assigned a Public IPv4 address such as 101.103.187.242 or an IPv6 address like 2000:f88b:4f63:5f8c:c0e8:5d78:309:5f78. It is possible to confirm these addresses by visiting https://test-ipv6.com/. However, conveying or referencing MAC addresses like c4:57:5f:b6:a1:22 to those who are not tech-savvy can lead to errors and complexity. Additionally, there is no provision of historical data, especially relating to past issues.
Navigating the World Wide Web
Accessing a webpage like https://simonis.biz typically involves a visit to a DNS server to convert the host component (simonis) in association with the Top Level Domain (biz) of the URL to an IP address, for example 27.172.202.104. When making web requests, the computer and browser provide information about their type, such as: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of Default Gateways
The default gateway is generally an address that is automatically configured via DHCP. It is common to receive a default gateway like 172.27.64.91 (typically ending in .1 or .254 depending on the scope size), and this serves as the point to which the computer forwards all its traffic. Further details on configuring IPv6 can be found in the blog post how-to-fix-ipv6-connectivity/, and it is possible to check on Mac or Linux using the following methods:
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 172.27.64.91 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:ebb3:30af:fbc5:13e1%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): {250.136.240.215, 76.6.212.210}
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 c4:57:5f:b6:a1:22
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 00:56:25:0c:1f:4b
}
Resolving Connectivity Issues for Wired or Wireless Networks
When it comes to transferring data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Guidelines for Apple’s macOS / OSX
Regardless of whether you are using OSX/macOS version 10.14.7, 11.5.5, or 12.1.2, there are various tools available for resolving connectivity issues. 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 practice remote work and Work From Anywhere (WFA).
Pre-installed Scripts That Offer Assistance
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings, and can also be configured to generate specific logs for troubleshooting. Furthermore, for a more comprehensive approach, the sysdiagnose tool can be used to generate a wide range of logs, although much of it pertains to wireless settings in a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (despite minimal interaction), you can execute sudo /usr/bin/sysdiagnose, which will result in a privacy warning. When running it in the foreground, it should open Finder in the correct location, or you can navigate to /var/tmp, or use Finder with Cmd+Shift+G to direct Finder to the specified path. However, be mindful of the file sizes, which are approximately 300MB or thereabouts.
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