Fix Apple IP Settings
Understanding Internet Addressing
When connecting to the Internet, users are assigned IP addresses, such as 199.173.120.132 for IPv4 or 2000:6dc5:1aec:5cae:1499:29ae:2c9e:e034 for IPv6. These can be verified at https://test-ipv6.com/, but communicating and remembering such addresses, or MAC addresses like 8b:88:b8:66:7f:0f, can be challenging, especially for non-technical individuals. Moreover, it lacks historical data for problem resolution.
Navigating Websites
Accessing a website, such as https://bernier-fisher.net, requires the translation of the URL’s host portion (bernier-fisher) and Top Level Domain (net) into an IP address, like 143.251.128.207, through a DNS server. Every web request from a computer and browser also includes its type, e.g. Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
The default gateway, typically assigned via DHCP with addresses like 172.23.230.72, serves as the central routing point for a computer’s outbound traffic. IPv6 connectivity issues can be resolved with a deep dive into how-to-fix-ipv6-connectivity/, and can be checked on Mac or Linux with a few simple commands.
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 172.23.230.72 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 fe80:5fa5:e126:35fe:e5c4%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): {185.224.120.147, 131.254.153.147}
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 8b:88:b8:66:7f:0f
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 9c:6c:96:1c:9d:cb
}
Fixing Connectivity Issues for Wired or Wireless Networks
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you’re using OSX or macOS versions such as 10.12.8, 11.2.2, or 12.2.4, there are various troubleshooting tools available. However, these tools and manual actions do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for remote work and Work From Anywhere (WFA) teams.
Handy Built-in Scripts to Assist You
One useful tool for OSX/macOS users is sudo wdutil info, which provides 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 wide range of logs, although many of these are only relevant to wireless matters and are not continuous like wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, usesudo nohup /usr/bin/sysdiagnose -u &. For an interactive experience, runsudo /usr/bin/sysdiagnose, which will display a privacy warning and open Finder in the correct location. Keep in mind that the file sizes can be around 300MB.
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