Fix Mac Issues

Understanding the Functioning of Internet Addressing

When using the Internet, individuals may be assigned a Public IPv4 address, such as 182.48.35.52, or an IPv6 address, like 2000:10e9:1d0c:165c:87bf:4357:d687:4a52. This information can be verified at https://test-ipv6.com/. However, explaining and communicating these addresses, or even referencing MAC addresses such as 8e:43:72:bf:ec:54, can be prone to errors and become complex quickly, particularly for those with limited technical knowledge. Furthermore, it does not provide any historical data, especially from previous issues.

Navigating the Internet

When attempting to access a website, like https://moen-reynolds.name, the first step involves requesting assistance from a DNS server to translate the host portion (moen-reynolds) combined with the Top Level Domain (name) of the URL into an IP address, for example, 81.7.73.213. Furthermore, the computer and browser specify their type with all web requests, such as
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36.

Understanding the Significance of Default Gateways

Generally, the default gateway is an address that is automatically configured via DHCP. This often translates to receiving a default gateway, such as 192.0.0.99 (though typically ending in .1 or .254 depending on the scope size), to which the computer sends all its traffic to be routed onwards. For a deeper understanding of this process for IPv6, refer to our detailed explanation at how-to-fix-ipv6-connectivity/. However, on Mac or Linux systems, verification can be done with:

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:a031:347a:271b:6550%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): {146.251.107.138, 20.196.250.207}
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 8e:43:72:bf:ec:54
  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 7c:1e:ea:3b:4c:c0
}

Resolving Issues with Wired and Wireless Connections

When it comes to transferring data, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer to send the data to your router.

Troubleshooting Steps for Apple macOS / OSX

Regardless of the version of OSX/macOS you are using - whether it’s 10.13.5, 11.5.1, or 12.2.4 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).

Pre-installed Scripts for Assistance

One useful tool on OSX/macOS is “sudo wdutil info,” which provides a dump of current wireless settings to the CLI, and can be configured to generate specific logs for troubleshooting purposes. Additionally, the “sysdiagnose” tool can be used to generate a wide range of logs, although much of it is related to wireless settings and is only relevant at a specific point in time.

To run it in the background and generate logs, use the command “sudo nohup /usr/bin/sysdiagnose -u &,” which will write logs to “/var/tmp/.tar.gz.” For interactive use, you can run “sudo /usr/bin/sysdiagnose,” which will prompt a privacy warning and open Finder in the correct location. Alternatively, 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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Table 1.0 - Video Help