How To Fix MacOS Issues
Understanding the Functionality of Internet Addressing
When using the Internet, individuals may have a Public IPv4 address, such as 116.133.92.138, or an IPv6 address, like 2000:f3d8:680c:12a3:4667:f80f:348e:a59e. Verification of these addresses can be done through https://test-ipv6.com/. Communication of these addresses or MAC addresses, such as 18:a4:b1:4c:1a:a5, can be prone to errors and complexity, especially for those who are not tech-savvy. Furthermore, it does not provide historical data, particularly when addressing past issues.
Navigating the Internet
To access a website, like https://zboncak.info, the process begins with accessing a DNS server to translate the host portion (zboncak) combined with the Top Level Domain (info) of the URL into an IP address, such as 203.11.138.190. Additionally, the computer and browser specify their type with every web request, for example, Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Understanding the Significance of Default Gateways
Typically, the default gateway is an automatically configured address via DHCP, such as 192.0.0.99 (although they usually end in .1 or .254, depending on the scope size). This gateway is where all computer traffic is routed for further processing. For IPv6 connectivity solutions, a detailed guide can be found at how-to-fix-ipv6-connectivity/, and it can be checked on Mac or Linux using:
codeblock
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 192.0.0.99 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 fe80:8f4c:3faa:81df:88a1%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): {43.144.165.56, 104.9.118.246}
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 18:a4:b1:4c:1a:a5
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 4e:7d:8b:87:c4:fd
}
Resolving Connectivity Issues for Wired and Wireless Networks
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.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.3, 11.2.8, or 12.1.5, there are various troubleshooting tools available. However, these manual actions and scripts have limitations when it comes to providing a series of correlated values over time. This is where automated remote troubleshooting becomes incredibly valuable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Effective Built-in Scripts
One particularly 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. Additionally, the sysdiagnose tool offers a more comprehensive option for generating various logs, although many of these are specific to a particular point in time in relation to wireless, similar to the wdutil tool.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in the /var/tmp/<blah>.tar.gz directory. For an interactive option (despite minimal interaction), you can run sudo /usr/bin/sysdiagnose, but be aware of the large file sizes of around 300MB. After running it, Finder should open in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G.
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