How Do You Support OSX No-access
Understanding the Basics of Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 address, such as 9.43.54.190, or an IPv6 address, like 2000:2968:4565:5e41:d9:e630:9385:b1b8. This information can be verified from https://test-ipv6.com/. However, for those who are not technically inclined, trying to share or identify these addresses, including MAC addresses like 5e:6b:f8:31:6e:b9, can be error-prone and complex. Moreover, it does not provide any historical data, particularly regarding past issues.
Navigating Through the World Wide Web
When accessing a website, such as https://dickens.biz, you begin by contacting a DNS server to convert the host portion (dickens) and the Top Level Domain (biz) of the URL into an IP address, such as 24.245.171.16. Your computer and browser include your device type in all web requests, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. This gateway, such as 10.20.125.230 (usually ending in .1 or .254 based on the scope size), is where your computer sends all its traffic to be forwarded. For IPv6, a comprehensive guide on how-to-fix-ipv6-connectivity/ is available, or you can verify this 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 10.20.125.230 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 fe80:2676:21dd:6a24:aada%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): {30.15.112.166, 70.18.74.80}
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 5e:6b:f8:31:6e:b9
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 61:d4:4f:c8:77:38
}
Fixing Issues with Wired and Wireless Connectivity
In order to transmit data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Problems on Apple’s macOS
Regardless of whether you are running OSX/macOS version 10.15.6, 11.4.3, or 12.1.1, there are various tools available for troubleshooting. While manual actions and scripts can be helpful, they do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have embraced remote work and the Work From Anywhere (WFA) concept.
Pre-Installed Scripts for Assistance
A highly useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless-related settings to the command line interface (CLI) and can also be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although most of the information is only relevant to wireless settings, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. For an interactive run (even though there is limited interaction), you can execute sudo /usr/bin/sysdiagnose, which will trigger a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp manually, or use Finder with Cmd+Shift+G to point Finder to the path. However, be mindful of the file sizes, which are approximately 300MB or slightly more.
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