Test OSX Internet
How IP Addresses Work
When using the Internet, you are assigned a unique IP address, such as 73.212.0.166 for IPv4 or 2000:f357:c93f:9fb0:4efe:d200:f16:1d69 for IPv6. To verify your IP address, visit https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even mentioning MAC addresses like b2:bc:fb:fa:cc:4d, can be prone to errors and become complex quickly. Furthermore, this method does not provide historical data, particularly when addressing past issues.
Navigating the Internet
Accessing a website like https://adams.name begins with contacting a DNS server to convert the host (adams) and the Top Level Domain (name) of the URL into an IP address, such as 251.166.176.17. When sending web requests, your computer and browser indicates their type, such as: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Understanding the Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP, leading to a default gateway like 192.0.0.85 (commonly ending in .1 or .254 based on the scope size). This is the point where your computer forwards all traffic to be routed further. For IPv6, detailed instructions can be found in our article how-to-fix-ipv6-connectivity/, and can also be checked in Mac or Linux 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 192.0.0.85 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:c4e4:f6d4:5910:8fe4%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): {69.5.218.200, 92.82.185.205}
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 b2:bc:fb:fa:cc:4d
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 52:36:23:5d:6a:05
}
Diagnosing Wired and Wireless Connectivity Issues
When it comes to transmitting data to your router, you may encounter connectivity issues at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Strategies for Apple macOS / OSX Troubleshooting
No matter which version of macOS or OSX you are using, whether it’s 10.13.1, 11.0.4, or 12.1.9, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, making it challenging to identify the root cause of connectivity issues. This is where automated remote troubleshooting becomes invaluable, especially for teams practicing remote work and Work From Anywhere (WFA) policies.
Leveraging Built-in Scripts for Troubleshooting
One useful tool on OSX/macOS is the sudo wdutil info command, which generates a dump of the current wireless settings and can be configured to produce specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive solution, generating a wide range of logs (although many are only relevant to the current 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. Alternatively, running sudo /usr/bin/sysdiagnose interactively will display a privacy warning and open Finder in the correct location. However, be mindful of the file sizes, which can be around 300MB.
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