How Can I Support Mac Connectivity
Understanding the Functioning of Internet Addressing
When using the Internet, you might have a Public IPv4 address such as 159.92.240.219 or an IPv6 address like 2000:7461:7ff6:7330:e996:896f:825b:92bb. This can be verified at https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or even mentioning MAC addresses like 85:64:69:f2:bd:08 can be prone to errors and become complex quite rapidly. Moreover, this does not provide any historical data, especially during previous issues.
Navigating the World Wide Web
In order to access a web page such as https://koelpin.info, the first step is to connect to a DNS server to convert the host part (koelpin) along with the Top Level Domain (info) of the URL into an IP address like 137.32.116.9. Your computer and browser actually includes its type with all web requests, for example Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. You receive a default gateway such as 10.129.165.169 (although they usually end in .1 or .254 depending on the scope size) and this is where your computer transmits all its traffic to be further routed. For IPv6, a thorough analysis is available at how-to-fix-ipv6-connectivity/ but it can be verified on Mac or Linux with:
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 10.129.165.169 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 fe80:2fd7:48a8:792a:457%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): {2.71.37.134, 221.231.251.109}
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 85:64:69:f2:bd:08
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 d1:d8:a4:d1:74:00
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS versions such as 10.15.4, 11.6.6, or 12.3.5, 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 are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A highly beneficial tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can also be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is specific to a particular point in time in relation to wireless, 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 (even though there isn’t much interaction), you can executesudo /usr/bin/sysdiagnose and it will prompt a privacy warning. When not run 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 direct it to the path. Keep in mind that the file sizes are approximately 300MB more or less.
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