How Can I Support Mac No-access
Functioning of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address, such as 147.176.174.229, or an IPv6 address, such as 2000:cec0:f13a:95b8:292:ca3b:8ff4:d8e3. This can be verified at https://test-ipv6.com/. However, for those who are not tech-savvy, communicating these addresses or even referencing MAC addresses like c0:b1:63:70:76:bb can be prone to errors and quickly become complex. Moreover, this method does not provide any historical data, particularly when dealing with past issues.
Navigating the World Wide Web
When attempting to access a webpage, such as https://metz-harvey.co, you first contact a DNS server to convert the host (metz-harvey) combined with the Top Level Domain (co) of the URL into an IP address, such as 89.62.211.82. Your computer and browser both denote their type with every web request, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
Significance of Default Gateways
The default gateway is usually an automatically assigned address via DHCP. For instance, you might receive a default gateway like 172.19.176.159 (typically ending in .1 or .254 depending on the scope size), which is where your computer sends all its traffic to be routed onwards. For IPv6, a detailed guide is available on how-to-fix-ipv6-connectivity/, but it can be checked 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 172.19.176.159 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 fe80:2b1f:31fb:103e:bef7%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): {214.61.165.223, 83.126.185.255}
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 c0:b1:63:70:76:bb
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 a4:28:97:cf:15:76
}
Fix Wired and Wireless Connectivity Issues
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 on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.13.9, 11.6.6, or 12.3.7, there are various troubleshooting tools available. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Helpful Built-in Scripts
One extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI, and can 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 data related to wireless, similar to wdutil.
By using sudo nohup /usr/bin/sysdiagnose -u & you can run the tool in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. Alternatively, you can run it interactively with sudo /usr/bin/sysdiagnose and it 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 be aware of the large file sizes, approximately around 300MB.
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P.S. Tips For Remote Network and Client Support
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