Check OSX Internet Connection
Explanation of Internet Addressing
When using the Internet, you will have a Public IPv4 address such as 62.113.82.97 or an IPv6 address like 2000:38af:e521:7bb0:6d47:db10:ba13:b7cb. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, attempting to convey these addresses, or even referencing MAC addresses like 88:43:f5:28:0b:ec, can lead to mistakes and become complicated. Furthermore, this method does not provide any historical data, especially from past issues.
How to Reach Websites
In order to access a webpage such as https://shanahan-wolf.io, the first step is to contact a DNS server to convert the host part (shanahan-wolf) in combination with the URL’s Top Level Domain (io) into an IP address like 211.196.145.6. When making web requests, your computer and browser also include information about their types, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. The default gateway is usually something like 10.254.243.135 (although they often end in .1 or .254 depending on the scope size), and it serves as the location where your computer sends all of its traffic to be routed further. For IPv6 issues, there is a more comprehensive guide available at how-to-fix-ipv6-connectivity/, but on Mac or Linux systems, you can perform a check using the following command:
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 10.254.243.135 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:c818:949a:1f09:3c55%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): {11.199.220.196, 185.25.234.93}
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 88:43:f5:28:0b:ec
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 f2:94:38:46:fe:00
}
Resolving Issues with Wired and 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 on Apple macOS / OSX
No matter which version of OSX/macOS you are working on, whether it’s 10.13.4, 11.1.9, or 12.1.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes extremely beneficial, especially for teams that have adopted remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One of the most helpful tools on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless-related settings, 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 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 is not much interaction), you can runsudo /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 with Cmd+Shift+G. Just be cautious of the file sizes, which are approximately 300MB.
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