How Do You Check OSX No-access
The Functioning of Internet Addressing
When using the Internet, you may be assigned a Public IPv4 address such as 40.45.141.90 or an IPv6 address like 2000:99ce:d471:3edf:8cd:713d:224d:9a6e. You can verify this by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, attempting to communicate these addresses or MAC addresses like a9:2b:c6:05:80:2e can be prone to error and can quickly become complex. Moreover, this method does not provide any historical data, particularly from past issues.
Navigating the World Wide Web
When attempting to access a web page such as https://conroy.name, the first step is to connect to a DNS server to convert the host portion (conroy) along with the Top Level Domain (name) of the URL into an IP address, such as 157.176.153.235. Furthermore, your computer and browser transmit its type with all web requests, for instance, Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
The Significance of Default Gateways
Usually, your default gateway is an address that is automatically configured via DHCP. A default gateway, such as 10.171.24.243 (typically ending in .1 or .254 depending on the scope size), is where your computer directs all its traffic to be routed further. For IPv6, detailed instructions are available on how-to-fix-ipv6-connectivity/, and 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 10.171.24.243 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 fe80:2ff3:fe40:2d76:5287%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): {57.228.206.125, 16.158.168.21}
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 a9:2b:c6:05:80:2e
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 16:d6:e9:3d:26:97
}
How to Resolve Issues with Wired and Wireless Connections
When sending data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Resolving Problems on Apple macOS / OSX Systems
Regardless of whether you are using OSX or macOS version 10.13.3, 11.1.9, or 12.2.5, there are various troubleshooting tools available. However, these manual methods and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have adopted remote work and a Work From Anywhere (WFA) approach.
Pre-installed Scripts That Can Offer Assistance
An extremely 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 logs for troubleshooting purposes. Moreover, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, the tool will run in the background and write logs to /var/tmp/<blah>.tar.gz. Alternatively, if you prefer to run it interactively (although there is minimal interaction), you can execute sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the designated location, allowing you to navigate to /var/tmp or use Cmd+Shift+G to point Finder to the path. However, be cautious of the file sizes, which can be approximately 300MB.
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