How Can I Support OSX No-access
Understanding Internet Protocol Addresses
When using the Internet, you are assigned a unique Public IPv4 address, such as 65.83.22.193, or an IPv6 address, for example 2000:61ec:6752:8c56:39e2:5924:7557:c4f4. This information can be verified at https://test-ipv6.com/. However, conveying these addresses, or even mentioning MAC addresses like 69:6b:ce:3c:ce:48, in a way that is understandable to those not familiar with technology can be prone to errors and quickly become complex. Furthermore, this does not provide any historical data, particularly when previous issues occurred.
Navigating through the World Wide Web
Accessing a web page like https://heathcote.biz involves initially connecting to a DNS server to convert the host portion (heathcote) combined with the Top Level Domain (biz) of the URL into an IP address, such as 139.247.203.188. Whenever your computer and browser make web requests, they also provide their specifications, for instance:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Significance of Default Gateways
The default gateway is typically an address assigned through DHCP. A default gateway, such as 192.168.169.114 (commonly ending in .1 or .254 depending on the scope size), is where your computer sends all its traffic to be routed to other destinations. For IPv6, detailed information can be found in our guide on how-to-fix-ipv6-connectivity/, or it can be checked on Mac or Linux using the following command:
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 192.168.169.114 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 fe80:98ef:2470:418f:f2cb%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): {199.125.103.192, 86.172.108.246}
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 69:6b:ce:3c:ce:48
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 d2:2d:d2:c3:33:ea
}
Troubleshooting and Resolving 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.
Resolving Connectivity Problems on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.1, 11.3.1, or 12.3.9, there are various tools available for diagnosing and resolving issues. However, these tools do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, particularly for teams that adopt remote work and Work From Anywhere (WFA).
Utilizing Built-in 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 also be configured to generate specific logs for troubleshooting. 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.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for interactive use, you can run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Be mindful of file sizes, which are typically around 300MB.
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