How Can I Support MacOS Connectivity
Demystifying Internet Addresses
When using the Internet, you are assigned a Public IPv4 address such as 65.154.182.10 or an IPv6 address like 2000:8afc:c923:3f6d:69a7:1d7d:e9ef:222b. You can verify this at https://test-ipv6.com/. However, for those who aren’t tech-savvy, conveying these addresses or MAC addresses like 90:4f:86:af:62:d1 can lead to errors and complexities, without providing historical data from previous incidents.
Navigating the World Wide Web
When accessing a website such as https://cronin.net, the first step is to access a DNS server to translate the host portion (cronin) and the Top Level Domain (net) of the URL into an IP address like 61.25.185.22. Every web request made by your computer and browser includes your browser type, for example:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
Understanding the Role of Default Gateways
Your default gateway is typically an automatically assigned address through DHCP, such as 192.168.91.232 (usually ending in .1 or .254 based on the scope size). This is the point to which your computer sends all its traffic to be routed further. For IPv6, more information can be found in our in-depth discussion on how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux with:
command to check default gateway
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 192.168.91.232 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:a2f8:51e:eef6:2590%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): {161.242.188.112, 7.146.207.24}
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 90:4f:86:af:62:d1
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 22:83:9b:33:48:c3
}
Fixing Connectivity Issues on Wired and Wireless Networks
When it comes to transferring data to your router, you might be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS versions like 10.15.1, 11.2.7, or 12.0.2, there are various tools available for troubleshooting. However, the manual actions and scripts provided do not offer a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings and can also be configured to generate specific logs for troubleshooting. Alternatively, the sysdiagnose tool can be used to generate a wide variety of logs, although much of it is only relevant to wireless at a specific point in time, much like 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 you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When 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. Be cautious of the file sizes, which are approximately 300MB.
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