How To Support Mac Connectivity
The Functionality of Internet Addressing
When browsing the internet, you are often assigned a Public IPv4 address such as 61.243.101.56 or an IPv6 address like 2000:6aa4:e962:c4a0:9e6b:bac7:7c22:c66d. It is possible to verify this information at https://test-ipv6.com/. However, explaining these addresses or even mentioning MAC addresses like 1d:40:83:c3:30:69, can be error-prone and complex, particularly for those who are not tech-savvy. Moreover, this method does not provide any historical data, especially when previous issues occurred.
Navigating the World Wide Web
In order to access a web page like https://durgan.org, you initially connect to a DNS server to convert the host section (durgan) combined with the Top Level Domain (org) of the URL into an IP address like 163.210.184.19. In every web request, your computer and browser will send its type, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Typically, your default gateway is an automatically configured address via DHCP. For instance, you may receive a default gateway like 172.24.50.255 (although they usually end in .1 or .254 depending on the scope size), which is where your computer sends all of its traffic to be routed onwards. There is a detailed explanation for IPv6 on how-to-fix-ipv6-connectivity/ but you can check 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 172.24.50.255 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 fe80:1bc:2b32:b7ba:b2ea%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): {14.215.144.81, 37.1.196.84}
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 1d:40:83:c3:30:69
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 b1:66:0a:6b:55:90
}
Resolve 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.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you have, whether it’s 10.11.4, 11.4.8, or 12.3.6, there are various troubleshooting tools available. However, these manual actions and scripts don’t provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless related settings to the CLI and can also be configured to 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 point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can runsudo /usr/bin/sysdiagnose, which will give 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. Just keep in mind that the file sizes are about 300MB or so.
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