How Can I Fix Mac Issues
Understanding Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 address, such as 246.215.80.247 or an IPv6 address like 2000:dc48:c98e:5ea0:c4ec:c44a:5e2c:36da. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, communicating and memorizing these addresses, including MAC addresses like e1:ed:f5:e3:39:9c, can be complicated and prone to errors. Furthermore, this method lacks historical data, especially in the context of past issues being encountered.
Navigating to Websites
When attempting to access a webpage, such as https://turner-kshlerin.co, the initial step involves reaching out to a DNS server to convert the host portion (turner-kshlerin) combined with the Top Level Domain (co) of the URL into an IP address, such as 216.239.205.25. Interestingly, your computer and browser include their types in all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. This address, such as 192.0.0.225 (although they generally end in .1 or .254 based on the scope size), is where your computer directs all its traffic to be routed onwards. For those interested in IPv6, a comprehensive guide is available on how-to-fix-ipv6-connectivity/, but users can also conduct a check on Mac or Linux with 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 192.0.0.225 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:c42:3cef:f90:bc63%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): {205.108.76.20, 29.219.61.70}
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 e1:ed:f5:e3:39:9c
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 84:11:63:90:34:eb
}
Resolving Connectivity Issues with 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.
Troubleshooting Tips for Apple’s macOS / OSX
Regardless of whether you are using OSX or macOS 10.14.1, 11.3.5, or 12.0.2, there is a variety of tools available for troubleshooting. However, manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Pre-installed Scripts for Assistance
A helpful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of 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 point-in-time information related to wireless, similar to wdutil.
By runningsudo nohup /usr/bin/sysdiagnose -u &, it will run in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use the commandsudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It is important to be aware of the file sizes, which are around 300MB.
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