How Can I Check OSX Issues
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 251.199.69.137 or an IPv6 address like 2000:1483:ba9c:e976:e7d2:37e1:36c8:f896. This can be verified at https://test-ipv6.com/. However, conveying these addresses, including MAC addresses like 24:c2:46:a0:d3:4f, poses challenges, especially for those who are not tech-savvy, and does not provide historical data.
Navigating the Internet
In order to access a website like https://kovacek.net, the DNS server must first translate the host portion (kovacek) and the Top Level Domain (net) of the URL into an IP address, such as 202.152.172.199. 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
The default gateway is usually an address automatically configured via DHCP, such as 172.23.72.214 (typically ending in .1 or .254, depending on the scope size). This is the point to which your computer sends all its traffic to be routed onwards. For IPv6, more information can be found in our post how-to-fix-ipv6-connectivity/, and you can perform a 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 172.23.72.214 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:c454:6ef9:9138:77f%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): {35.114.197.249, 204.116.246.32}
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 24:c2:46:a0:d3:4f
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 fc:8c:70:f3:35:b6
}
Debugging Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions like 10.13.3, 11.2.6, or 12.2.3, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams practicing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which displays current wireless settings and can be configured to generate specific troubleshooting logs. Moreover, the sysdiagnose tool provides a comprehensive range of logs, although much of the information is only relevant at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the following command: sudo nohup /usr/bin/sysdiagnose -u &. For an interactive (albeit minimal interaction) run, use sudo /usr/bin/sysdiagnose and be prepared for a privacy warning. If not running in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Cmd+Shift+G in Finder. It’s important to note that the file sizes are approximately 300MB.
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