Support MacOS Internet Connection
How IP Addressing Functions
When using the Internet, you are assigned a Public IPv4 address such as 167.164.25.138 or an IPv6 address like 2000:d32a:1677:216e:d20f:18bf:1023:4753. Confirmation of this information can be done at https://test-ipv6.com/. However, conveying these addresses, and even MAC addresses like 58:df:f1:cb:e0:b8 to non-technical individuals can be complex and error-prone. Additionally, these methods do not provide any historical information.
Navigating the Internet
To access a website like https://fahey.com, the DNS server is initially contacted to convert the host portion (fahey) combined with the Top Level Domain (com) of the URL into an IP address such as 241.96.216.170. Additionally, your computer and browser include information about the web request type, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
The Significance of Default Gateways
Typically, the default gateway is an address that is automatically configured via DHCP. This address, such as 192.0.0.118 (usually ending in .1 or .254) is where your computer directs all its traffic to be routed onwards. For IPv6 connectivity, a comprehensive guide is available at how-to-fix-ipv6-connectivity/. Alternatively, on Mac or Linux systems this can be checked 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 192.0.0.118 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 fe80:1e81:527e:e1a2:c9d0%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): {18.160.212.76, 39.160.81.197}
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 58:df:f1:cb:e0:b8
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 71:31:d3:64:d7:89
}
Fixing Connectivity Issues on macOS Devices
When dealing with connectivity issues at the physical and data layer, it’s important to consider whether you are using a wired or wireless (Wi-Fi) medium to send data to your router.
Troubleshooting Tools for Various Versions of macOS
Regardless of whether you are using macOS versions such as 10.14.7, 11.1.3, or 12.1.7, there are a variety of tools available for troubleshooting. However, the manual actions and scripts provided do not offer a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are fully embracing remote work and a Work From Anywhere (WFA) approach.
Effective Built-in Scripts
A useful tool on macOS is the sudo wdutil info command, which provides a dump of current wireless-related settings to the CLI. It’s also possible to configure this to generate specific logs for troubleshooting. Alternatively, the sysdiagnose tool offers a more comprehensive solution for generating a wide range of logs, although much of it is point-in-time information related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. For an interactive experience (although there is minimal interaction), you can run sudo /usr/bin/sysdiagnose, which will display a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to be mindful of the large file sizes, approximately 300MB or more.
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