DiagnOSe MacOS Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 136.59.216.23, or an IPv6 address, like 2000:d7ff:808d:87a3:807e:f41a:d1a3:fe31. You can verify this information by visiting https://test-ipv6.com/. However, explaining these addresses to non-technical individuals, or even referencing MAC addresses like 5b:46:fb:98:0d:0d, can be prone to errors and become complex. Furthermore, this method does not provide historical data, particularly from past issues.
Navigating the Web and the Process of Lookups
When accessing a website such as https://bogan.io, you first contact a DNS server to convert the host portion (bogan) combined with the Top Level Domain (io) of the URL into an IP address, like 224.86.183.142. Your computer and browser transmit its type with all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Your default gateway is usually an automatically assigned address via DHCP, such as 172.30.2.150 (although they normally end in .1 or .254 depending on the scope size). This is where your computer sends all its traffic to be routed onwards. For IPv6, you can refer to an in-depth guide on how-to-fix-ipv6-connectivity/, or check on Mac or Linux 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 172.30.2.150 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 fe80:135b:cf0f:a621:acb8%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): {210.142.90.160, 146.233.62.65}
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 5b:46:fb:98:0d:0d
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 66:19:41:f3:65:23
}
Resolving Connectivity Issues for Wired and Wireless Networks
When it comes to sending 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’re running OSX/macOS version 10.11.3, 11.4.5, or 12.1.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts and Commands
A very helpful tool on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only point-in-time in relation to wireless, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will give a privacy warning. If 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. Keep in mind that the file sizes are about 300MB more or less.
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 🏠🏝🛰.
