How Can I Fix Mac Connectivity

The Functioning of Internet Addressing

When using the Internet, it is common to have a Public IPv4 address such as 212.84.195.86 or an IPv6 address like 2000:c8be:793e:7031:3fb7:414d:7193:ef78. This information can be verified from https://test-ipv6.com/. However, for those who are not technologically inclined, conveying these addresses or even mentioning MAC addresses like af:45:e9:b8:0d:24 can be prone to errors and can become complicated quickly. Furthermore, this does not provide any historical data, particularly in the past when previous issues arose.

Navigating the Internet

Accessing a website such as https://kris.name initially involves communicating with a DNS server to translate the host part (kris) along with the Top Level Domain (name) of the URL, into an IP address like 101.173.54.97. Your computer and browser sends its type with all web requests, for example:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36

The Significance of Default Gateways

By default, your gateway is usually an address that is automatically configured via DHCP. You receive a default gateway like 192.0.0.131 (although they usually end in .1 or .254 depending on the scope size) and this is where your computer sends all its traffic to be routed onwards. For IPv6, we have an in-depth discussion on how-to-fix-ipv6-connectivity/, but you can verify it on Mac or Linux 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  192.0.0.131    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:acb1:714d:d8ec:c3d9%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): {29.207.215.122, 106.204.14.227}
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 af:45:e9:b8:0d:24
  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 47:b7:01:ad:d9:45
}

Resolving Issues with Wired and Wireless Connections

When it comes to transmitting data to your router, you may be using 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 currently using, whether it’s 10.14.5, 11.6.6, or 12.0.3, there are various tools available for troubleshooting. However, these tools and manual actions fail to provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for remote work and Work From Anywhere (WFA) teams.

Useful Built-in Scripts

A highly beneficial tool on OSX/macOS is “sudo wdutil info,” which provides a dump of current wireless settings in 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 settings and is similar to wdutil.

To run the sysdiagnose tool in the background and generate logs in “/var/tmp/.tar.gz,” use the command “sudo nohup /usr/bin/sysdiagnose -u &.” For an interactive version, use “sudo /usr/bin/sysdiagnose,” which will prompt a privacy warning. If it’s not run in the background, it should open Finder in the correct location, or you can navigate to “/var/tmp” or use Finder with Cmd+Shift+G to locate the path. However, be cautious of the file sizes, which are typically around 300MB.

Possibly Helpful Videos

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Table 1.0 - Video Help