Support MacOS IP Settings
Explanation of Internet Addressing
When using the Internet, you will be assigned a public IPv4 address such as 92.50.62.57 or an IPv6 address like 2000:7d3a:f785:7fc3:1a19:4f8d:78bf:4171. To verify your address, you can use the https://test-ipv6.com/ website. However, attempting to communicate or transmit these addresses to individuals who are not technologically savvy can lead to errors and complications, particularly when trying to share MAC addresses like 7f:a8:3a:b1:42:43. Moreover, these addresses do not provide any historical context, especially when problems have occurred in the past.
Navigating the World Wide Web
In order to access a website such as https://kris.name, your request is initially routed to a DNS server to convert the host section (kris) combined with the Top Level Domain (name) of the URL, into an IP address, such as 121.2.181.0. Notably, your computer and browser sends its type with all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Typically, your default gateway is automatically assigned via DHCP and takes the form of an address such as 172.26.77.214 (usually ending in .1 or .254 based on the scope). This is the location where your computer directs all its traffic to be further routed. For a more detailed explanation on IPv6, refer to our comprehensive guide on how-to-fix-ipv6-connectivity/. To check on Mac or Linux, use the following command.
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 172.26.77.214 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 fe80:1222:ebf3:4ed2:d3%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): {113.33.43.254, 249.120.228.98}
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 7f:a8:3a:b1:42:43
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 88:c1:ab:02:84:e6
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either 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 using, whether it’s 10.11.4, 11.0.7, or 12.0.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless related settings and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can generate a wide range of logs, although much of it is point in time only in relation to wireless, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose but be cautious of the file sizes, which can be around 300MB or more.
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