Fix Mac Connectivity
Understanding Internet Address Allocation
When using the Internet, you are assigned a Public IPv4 address such as 55.210.50.13 or an IPv6 address like 2000:bd60:9661:ee38:e762:656c:ea48:ccac. These can be verified at https://test-ipv6.com/. However, for those who are not technology-savvy, conveying these addresses, or even referring to MAC addresses like 3d:f2:92:aa:59:3d, can be prone to errors and quickly become complex. Moreover, this does not provide any historical data, particularly for past issues.
Navigating Through the World Wide Web
When attempting to access a website such as https://turner-skiles.org, you start by contacting a DNS server to convert the host part (turner-skiles) along with the URL’s Top Level Domain (org) into an IP address like 157.30.75.183. Your computer and browser always transmit their type in all web requests, as seen here: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is usually a preconfigured address obtained via DHCP. It assigns a default gateway, such as 192.168.96.245 (although they usually end in .1 or .254 based on the scope size), where your computer sends all its traffic to be routed further. For IPv6, you can refer to our comprehensive guide on how-to-fix-ipv6-connectivity/ or check on Mac or Linux platforms 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 192.168.96.245 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 fe80:5847:558b:abc9:f31%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): {63.252.56.155, 158.36.102.208}
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 3d:f2:92:aa:59:3d
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 98:2e:f8:b3:84:30
}
Resolve Problems with Wired or Wireless Connections
When it comes to sending data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX Devices
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.6, 11.0.8, or 12.1.9, there are various tools available for resolving issues. However, despite the manual actions and scripts, they do not offer a set of correlated values over time. This is where automated remote troubleshooting becomes incredibly useful, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Use of Pre-installed Scripts for Assistance
One extremely beneficial tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless related settings to the CLI, and can also 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 at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, although it will display a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to direct Finder to the correct path. Keep in mind that the file sizes will be around 300MB more or less.
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