How Do You Troubleshoot OSX Internet
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 or IPv6 address, such as 126.118.137.180 or 2000:59f:90b1:1bc4:adcb:6473:995f:4d5d. You can verify your address using https://test-ipv6.com/. However, conveying these addresses, or even MAC addresses like 89:0b:d1:b6:6f:fb to those who are not tech-savvy can be prone to errors and quickly become complex. Furthermore, this information does not provide any historical data, especially when previous issues occurred.
Navigating the World Wide Web
When accessing a website like https://collier.io, your computer first contacts a DNS server to translate the host portion (collier) and the Top Level Domain (io) of the URL into an IP address, such as 126.93.88.196. Your computer and browser also include its type with all web requests, for example:Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
The Significance of Default Gateways
Your default gateway is typically assigned automatically through DHCP, resulting in an address such as 192.0.0.20 (although they usually end in .1 or .254 depending on the scope size). This is where your computer directs all its traffic to be routed onwards. For more information on IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/. If you are using Mac or Linux, you can check the default gateway 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 192.0.0.20 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:b5d3:e8c0:268:1060%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): {122.28.227.220, 240.29.60.191}
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 89:0b:d1:b6:6f:fb
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 ea:59:1e:4d:78:e6
}
Troubleshooting Connectivity Issues on Apple Operating Systems
When it comes to sending data to your router, you might be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Effective Solutions for OSX and macOS
Regardless of the version of OSX/macOS you have, whether it’s 10.13.3, 11.5.3, or 12.3.2, there are multiple tools available for troubleshooting. However, these tools only offer isolated values and do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that support remote work and Work From Anywhere (WFA).
Useful Built-in Tools
One particularly useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI. This tool can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although some are only point-in-time related to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run (although there is not much interaction), use sudo /usr/bin/sysdiagnose, which will display 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 Cmd+Shift+G in Finder. Be mindful of the file sizes, which are approximately 300MB.
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