How To Support Mac No-access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 110.158.29.60 or an IPv6 address like 2000:b506:f819:87f1:2a48:3539:fde8:89b9. You can verify this information by visiting https://test-ipv6.com/. However, explaining these addresses, or even mentioning MAC addresses like 0a:7e:a4:1d:e1:60, can be complex and prone to errors, especially for those not well-versed in technology. Additionally, this method does not provide any historical data, particularly regarding past issues.
Navigating the World Wide Web
When accessing a website such as https://rowe.io, your computer first contacts a DNS server to convert the host name (rowe) and the Top Level Domain (io) of the URL into an IP address like 207.166.55.26. Interestingly, your computer and browser transmit their type with every web request, such as
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
Significance of Default Gateways
The default gateway is typically assigned automatically through DHCP and is usually an address ending in .1 or .254, depending on the scope size. This is where your computer directs all its traffic to be routed onwards. You can delve deeper into IPv6 connectivity by visiting how-to-fix-ipv6-connectivity/ or check 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 172.31.79.186 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:b1de:e4b0:1090:328b%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): {135.184.84.88, 91.16.92.83}
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 0a:7e:a4:1d:e1:60
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:cf:7f:bc:24:81
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Solutions for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.12.8, 11.1.9, or 12.2.2, there are various 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 invaluable, especially for teams that endorse remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A highly beneficial tool on OSX/macOS is sudo wdutil info, which delivers current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
Using sudo nohup /usr/bin/sysdiagnose -u & will run the tool in the background and write logs to /var/tmp/<blah>.tar.gz. For an interactive run (with minimal interaction), you can use sudo /usr/bin/sysdiagnose, keeping in mind the privacy warning that comes with it. 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 to point it to the path. Be mindful of the file sizes, which are approximately 300MB.
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