DiagnOSe MacOS Internet
–
Understanding Internet Addressing
When using the Internet, you may have a Public IPv4 address such as 153.64.225.225 or an IPv6 address like 2000:37e9:6e5b:6098:6400:9c10:fd45:ac7e. These can be verified from https://test-ipv6.com/. However, for those who are not familiar with technical aspects, communicating these addresses, or even mentioning MAC addresses like 5e:22:83:bc:93:04, can be prone to errors and quickly become complex. Moreover, this does not provide any historical data, especially when past issues occurred.
Navigating the Web and the Process of Lookups
When accessing a webpage like https://bashirian.org, you first reach a DNS server to translate the host portion (bashirian) along with the Top Level Domain (org) of the URL to an IP address like 188.17.244.84. Your computer and browser actually 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.
The Significance of Default Gateways
Your default gateway is usually an automatically configured address via DHCP. You receive a default gateway like 172.28.31.200 (although they typically end in .1 or .254 based on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, a detailed explanation can be found at how-to-fix-ipv6-connectivity/, but you can verify 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 172.28.31.200 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:ee07:e991:26f6:b3a5%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): {49.87.74.144, 209.132.112.27}
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 5e:22:83:bc:93:04
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 b2:7a:6a:29:e0:06
}
Fixing Connectivity Issues for Wired and Wireless Networks
In the realm of networking, the use of either a wired or wireless (Wi-Fi) medium at the physical and data layer is common when transmitting data to your router.
Resolving Problems on Apple macOS / OSX
Regardless of whether your system is running on OSX/macOS versions like 10.12.2, 11.0.4, or 12.1.7, there are a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of interconnected values over time. This is where automated remote troubleshooting proves to be beneficial, especially for teams that adopt remote work and Work From Anywhere (WFA) culture.
Utilizing Built-in Scripts and Commands for Assistance
An extremely valuable diagnostic tool on OSX/macOS is sudo wdutil info, which imparts a dump of the current wireless settings to the CLI. This tool can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool offers a more comprehensive approach, generating a wide range of logs (though much of it is only relevant to wireless at a specific point in time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will create logs in /var/tmp/<blah>.tar.gz. For an interactive (albeit limited) experience, you can executesudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the designated location or you can manually navigate to /var/tmp or use Finder with Cmd+Shift+G to pinpoint the path. Be cautious of the file sizes, which can amount to around 300MB.
Related 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 🏠🏝🛰.
