How Can I Troubleshoot OSX Internet
Understanding the Function of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 53.190.89.103 or an IPv6 address like 2000:c876:4b42:304f:aaad:e3e0:382:b575. This can be confirmed by visiting https://test-ipv6.com/. However, conveying these addresses, or even referencing MAC addresses such as e2:06:4c:d4:56:91, can be prone to error and quickly becomes complex, especially for those who are not technologically inclined. Furthermore, these addresses do not provide historical data, particularly from past issues.
Navigating the Internet
When attempting to access a website like https://harvey.info, the first step is to consult a DNS server to convert the host portion (harvey) combined with the Top Level Domain (info) of the URL into an IP address, such as 134.87.167.182. Whenever a web request is made, the computer and browser both disclose their type, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts).
Understanding the Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. This can manifest as a default gateway like 172.16.68.58 (often ending in .1 or .254 depending on the scope size), and is where a computer directs all of its traffic to be forwarded. While there is a comprehensive guide on how-to-fix-ipv6-connectivity/ for IPv6 concerns, it can also be verified on Mac or Linux through the following steps:
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 172.16.68.58 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 fe80:24bb:de5f:1740:f00a%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): {132.201.81.227, 10.124.64.92}
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 e2:06:4c:d4:56:91
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 fe:50:f1:17:a0:04
}
How to Resolve Issues with Wired and Wireless Connections
When transferring data to your router, it’s essential to troubleshoot any issues that may arise when using wired or wireless (Wi-Fi) connections.
Troubleshooting Tips for Apple macOS / OSX Users
Whether you’re running macOS or OSX versions such as 10.11.2, 11.0.4, or 12.2.5, there are various tools available for troubleshooting. However, these manual actions and scripts don’t provide a comprehensive set of correlated values over an extended period of time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that are adopting remote work and Work From Anywhere (WFA) practices.
Effective Built-in Scripts
A useful tool on OSX/macOS is sudo wdutil info, which provides a detailed dump of the current wireless settings through the CLI. It can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a wide range of logs, although much of it is only relevant to a specific point in time in relation to wireless, similar to the functionality of wdutil.
To run the sysdiagnose tool in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, although this 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 to locate the files. Keep in mind that the file sizes can be around 300MB or more.
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