How Can I Check MacOS Issues
A Look into the Functioning of Internet Addresses
When browsing the web, you are assigned a Public IPv4 address such as 20.40.201.185 or an IPv6 address like 2000:889b:593e:fe4b:335d:b44d:56c4:656a while being on the Internet. To verify these addresses, you can visit https://test-ipv6.com/. However, conveying these addresses to individuals not well-versed in technology or even mentioning MAC addresses like b9:37:bb:78:f1:a7 can lead to errors and become complex quickly. Moreover, this method does not provide any historical data, particularly from the time when previous issues occurred.
Navigating through the Internet
Upon wanting to visit a webpage like https://ledner-powlowski.name, you first encounter a DNS server that translates the host portion (ledner-powlowski) along with the Top Level Domain (name) of the URL to an IP address such as 143.157.148.40. Whenever making web requests, your computer and browser include its type, for instance Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36.
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically configured address via DHCP. You are provided with a default gateway like 172.28.225.60 (usually ending in .1 or .254 based on the scope size), and this is where your computer directs all its traffic to be routed further. For IPv6, we delve into details in our article how-to-fix-ipv6-connectivity/ or 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 172.28.225.60 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 fe80:24f0:873a:ecaf:b668%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): {147.38.181.255, 94.160.111.32}
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 b9:37:bb:78:f1:a7
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 75:1e:12:ba:8c:f8
}
Solutions for Resolving Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you have the option to do so through a wired or wireless (Wi-Fi) medium at the physical and data layer.
Steps to Take on Apple macOS / OSX Systems
Regardless of which version of macOS or OSX you are using, whether it’s 10.15.6, 11.6.8, or 12.0.6, there are various tools available for troubleshooting. However, the manual actions and scripts are unable to provide a set of correlated 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).
Pre-Installed Scripts That Are Useful
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless-related settings to the command line interface (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 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 write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there isn’t much interaction), you can use the command 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 Finder’s Cmd+Shift+G shortcut. Just be cautious of the file sizes, which are approximately 300MB more or less.
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