How Can I Troubleshoot Mac Internet
Explaining the Function of Internet Addressing
When using the Internet, it is common to have a Public IPv4 address such as 130.42.20.92 or an IPv6 address like 2000:6f5d:9119:b458:e626:d040:23a2:e7c1. Confirming this can be done at https://test-ipv6.com/. However, translating these addresses, or even specifying MAC addresses like 27:8a:79:33:4c:d8 to non-technical individuals can be prone to errors and can become complex quickly. Furthermore, this does not provide any historical information, especially pertaining to previous issues.
Navigating the World Wide Web
When attempting to access a web page such as https://hickle-wuckert.biz, the first step is to contact a DNS server to convert the combination of the host portion (hickle-wuckert) and the Top Level Domain (biz) of the URL into an IP address like 95.223.142.77. Every web request from your computer and browser includes its type, for example, Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
By default, your gateway is typically an automatically configured address through DHCP. A default gateway, such as 192.0.0.42 (although they usually end in .1 or .254 depending on the scope size), is where your computer sends all of its traffic to be routed further. To delve deeper into IPv6 and its connectivity solutions, refer to how-to-fix-ipv6-connectivity/ where you can also verify on Mac or Linux using:
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 192.0.0.42 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:d0ea:aa3f:e7b0:2b27%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): {99.77.90.46, 178.62.7.147}
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 27:8a:79:33:4c:d8
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 ce:99:bf:c0:03:19
}
Fixing Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be utilizing 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 10.15.5, 11.1.2, or 12.2.6, there are various troubleshooting tools available. However, these tools do not provide a series of correlated values over time, which is essential for remote troubleshooting, especially for teams working remotely and adopting the Work From Anywhere (WFA) principle.
Pre-Installed Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI, and can be configured to generate specific logs for troubleshooting purposes. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although most of it is only relevant to wireless connectivity, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, the tool can be executed in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which are around 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 🏠🏝🛰.
