How To Support OSX IP Settings
Functioning of Internet Address Allocation
When using the Internet, you can be assigned with a Public IPv4 address, such as 166.149.91.216, or an IPv6 address, like 2000:b859:e17:2f55:128a:b891:d7b5:3bef. Visit https://test-ipv6.com/ to verify your assigned IP address. However, explaining these addresses or MAC addresses like c6:b2:5f:7a:b4:ff to those not familiar with technology can be prone to errors and can become complex quickly. Furthermore, historical data is not provided, particularly when resolving past issues.
Navigating the Internet
In order to reach a website such as https://hintz-oreilly.info, you initially connect to a DNS server which converts the host segment (hintz-oreilly) along with the Top Level Domain (info) of the URL to an IP address, such as 40.104.125.244. Your computer and browser also transmit their type with all web requests, for example, Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. You are given a default gateway, such as 172.27.60.83 (usually ending in .1 or .254 based on the scope size), and this is where your computer directs all its traffic for further routing. In the case of IPv6, an in-depth exploration is available at how-to-fix-ipv6-connectivity/. To verify this on Mac or Linux, use:
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 172.27.60.83 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 fe80:137:e990:1dce:66ae%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): {235.185.227.58, 198.246.127.123}
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 c6:b2:5f:7a:b4:ff
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 aa:78:0b:e0:16:32
}
Solve Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you might be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Problems on Apple macOS / OSX Systems
Regardless of which version of OSX/macOS you’re operating on - whether it’s 10.14.1, 11.0.7, or 12.0.4 - there are various tools available for troubleshooting. However, the manual actions and scripts lack the ability to provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Utilize the Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless-related settings to the CLI and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although much of it is only applicable to wireless settings, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can utilize 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 Cmd+Shift+G in Finder. Keep in mind the file sizes, which are around 300MB or so.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
