Understand OSX No-access
Understanding Internet Addressing
When using the Internet, you are assigned either a Public IPv4 address, such as 197.137.86.6, or an IPv6 address, such as 2000:30ae:1e8e:c11e:6f77:60bd:18fa:b1c2. You can verify this through https://test-ipv6.com/. However, explaining these addresses, and even MAC addresses like bf:f8:8d:0e:37:52, to non-technical individuals can be complicated and error-prone. Furthermore, this method lacks historical data, especially for past issues.
Navigating the World Wide Web
When accessing a web page, such as https://harris.info, you first contact a DNS server to convert the combination of the host portion (harris) and the Top Level Domain (info) into an IP address, like 197.32.91.206. Your computer and browser include its type in all web requests, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is typically an address automatically configured via DHCP. It usually ends in .1 or .254 based on the scope size, such as 10.165.234.44, and serves as the point where your computer forwards all its traffic. For IPv6, you can reference our in-depth guide on how-to-fix-ipv6-connectivity/, or 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 10.165.234.44 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:ccf8:854b:2ac8:751f%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): {154.17.66.27, 254.118.124.204}
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 bf:f8:8d:0e:37:52
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 2d:d7:8b:14:e6:67
}
Fixing Issues with Wired and Wireless Connectivity
When it comes to sending data to your router, you may be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS version 10.15.8, 11.0.2, or 12.3.8, there is a variety of 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 are engaged in remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Support
A highly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant at a specific point in time in relation to wireless, similar to wdutil.
To run it in the background and generate logs at /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, but beware of the large file sizes of about 300MB.
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