Fix OSX Internet Connection
The Fundamentals of Internet Addressing
In the realm of the Internet, individuals may possess a Public IPv4 address, such as 66.234.28.217, or an IPv6 address like 2000:ca31:c782:76e8:b6c9:b236:725b:e0ba. This information can be confirmed at https://test-ipv6.com/. However, conveying or referencing these addresses and even MAC addresses like 5b:15:bc:de:11:93 can pose challenges for those not well-versed in technology, and the situation can become complex rather quickly. Moreover, this method does not provide historical data, particularly from previous occurrences of issues.
Navigating the World Wide Web
Accessing a webpage, such as https://kuvalis.io, entails initially reaching out to a DNS server in order to translate the host portion (kuvalis) in combination with the Top Level Domain (io) of the URL into an IP address (e.g., 201.16.62.222). It is worth noting that a computer and browser disclose their type with all web requests, for instance:
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
Typically, a default gateway is automatically configured via DHCP. A default gateway, such as 172.31.47.217 (usually ending in .1 or .254 depending on the scope size), is where a computer directs all its traffic to be routed onwards. Visit how-to-fix-ipv6-connectivity/ for an in-depth analysis on IPv6, or refer to the following command for checking on Mac or Linux:
ifconfig | grep -B 6 -m 1 "inet6 addr:"
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 172.31.47.217 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 fe80:2cec:a120:9b9b:1fac%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): {142.26.115.213, 53.187.192.228}
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 5b:15:bc:de:11:93
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 d9:e1:f6:41:37:4b
}
Fixing Issues with Wired or Wireless Networks
When it comes to sending data to your router, you might be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple Operating Systems
Regardless of whether you’re using OSX/macOS versions such as 10.12.7, 11.0.9, or 12.2.7, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that follow a remote work or Work From Anywhere (WFA) approach.
Effective Built-in Scripts
A highly useful tool on OSX/macOS is the sudo wdutil info command, which offers a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a comprehensive range of logs related to wireless issues, although many are only point-in-time observations similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs at /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there isn’t much interaction), you can execute sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Just keep in mind that the file sizes are typically around 300MB.
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