How Do You Understand Mac No-access
Understanding Internet Addressing
When using the internet, you are assigned a public address which could be either a Public IPv4 address, such as 122.211.230.133, or an IPv6 address, like 2000:95a7:f628:12ec:efb6:9d8e:2bbc:2b5e. https://test-ipv6.com/ can be used to check your assigned address. However, the challenge arises when trying to communicate and relay these addresses to individuals with limited technical expertise, especially when trying to call out complicated MAC addresses such as 15:ee:8e:19:7a:4c. In addition, there is no historical data provided for identifying recurring issues.
Navigating Web Access
When attempting to access a web page, such as https://heathcote.name, the process initially involves connecting to a DNS server, which translates the chosen domain name (heathcote) along with the Top Level Domain (name) of the URL to an IP address, such as 225.179.124.3. Remarkably, the browser and computer communicate specific details along with every web request, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. The default gateway, such as 192.0.0.35 (commonly ending in .1 or .254 based on scope size), serves as the primary routing destination for all computer traffic. While troubleshooting connectivity issues for IPv6, detailed information can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, the default gateways can be verified 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 192.0.0.35 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:b8a2:e4a4:fe4:ac44%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): {114.208.143.231, 50.46.60.212}
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 15:ee:8c:19:7a:4c
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 01:91:ef:09:85:7b
}
Fixing Connectivity Issues for Wired and Wireless Networks
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.1, 11.5.5, or 12.1.9, there are various troubleshooting tools available. However, these 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).
Utilizing In-Built Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs (although much of it is point in time only in relation to wireless, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there isn’t much interaction), you can runsudo /usr/bin/sysdiagnose, which 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 point Finder to the path. Just be aware of the file sizes, which are approximately 300MB more or less.
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