How To Support OSX No-access
Understanding IP Addressing
When connecting to the Internet, you will receive either a Public IPv4 address, such as 19.155.33.247, or an IPv6 address, like 2000:5a23:839d:9dd1:698a:60a8:b390:4fc2. You can verify this by visiting https://test-ipv6.com/. However, conveying these addresses, along with MAC addresses like 82:1c:88:2b:d5:9c, can be challenging for those not well-versed in technology. This becomes even more complex due to the lack of historical data.
Navigating to Websites
In order to access a particular webpage, for instance, https://casper.io, you first need to contact a DNS server to convert the host section (casper) in combination with the Top Level Domain (io) of the URL into an IP address, such as 60.203.253.73. When making web requests, your computer and browser also send information regarding their type, as seen in this example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
Your default gateway is typically assigned automatically via DHCP and appears as an address like 10.99.171.4 (although it generally ends in .1 or .254, based on the scope size). This is the point your computer uses to route all its traffic. For IPv6, you can delve deeper into the topic by visiting how-to-fix-ipv6-connectivity/ or check on Mac or Linux using the provided commands.
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 10.99.171.4 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 fe80:532:d3ad:d212:41f7%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): {142.187.152.99, 110.116.202.231}
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 82:1c:88:2b:d5:9c
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 c5:6d:d4:d4:46:ad
}
Resolving Connection Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Apple macOS / OSX Users
Regardless of whether you are running 10.12.2, 11.0.8, or 12.2.1, there are various troubleshooting tools available for macOS/OSX. However, these manual interventions and scripts do not provide a series of correlated values over time, making automated remote troubleshooting essential, particularly for teams embracing remote work and Work From Anywhere (WFA).
Leveraging Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Furthermore, the more comprehensive sysdiagnose tool can be utilized to generate a wide range of logs (although many are 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 an interactive experience (although there is minimal interaction), 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 correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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