How To Support Mac IP Settings
Understanding Internet Addressing
When connecting to the Internet, you are assigned a unique Public IPv4 address, such as 59.184.84.26, or an IPv6 address like 2000:3a3b:2f55:4763:e0f:782b:186c:e3ba. These addresses can be checked using https://test-ipv6.com/. However, conveying these addresses, along with MAC addresses like f3:26:64:2e:86:8a, can be challenging for those not well-versed in technology, and it can become complicated quickly. Furthermore, this information does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When accessing a website, such as https://okuneva.org, your device initially communicates with a DNS server to translate the host portion (okuneva) combined with the Top Level Domain (org) of the URL to an IP address, such as 82.209.128.55. Furthermore, your computer and browser send their type with every web request, for example:
<br>Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP, such as 192.0.0.145, although they normally end in .1 or .254 depending on the scope size. This is where your computer routes all its traffic. For IPv6, you can explore further using how-to-fix-ipv6-connectivity/ or check on Mac or Linux with 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 192.0.0.145 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 fe80:709f:bc2f:8fc5:4a28%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): {246.225.123.180, 100.125.135.84}
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 f3:26:64:2e:86:8a
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 90:c1:de:e2:6f:f1
}
Find Solutions for Wired or Wireless Connection Issues
When it comes to transmitting data at the physical and data layer, you might be using a wired or wireless (Wi-Fi) medium to send information to your router.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you are running, whether it’s 10.12.2, 11.3.8, or 12.1.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless related settings and can be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can generate a wide range 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 it 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 give a privacy warning. When 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 point Finder to the path. However, be mindful of the file sizes, which are approximately 300MB more or less.
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