How Can I DiagnOSe Mac IP Settings
Understanding Operation of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 98.255.209.64 or an IPv6 address like 2000:4a5c:b3f:bb4d:784c:d1b2:b34a:b53e. Verification of these addresses can be done at https://test-ipv6.com/. However, expressing these addresses or MAC addresses like d5:a8:87:3c:97:8a can be challenging, especially for those without technical expertise. Furthermore, this method does not provide historical data, particularly for past issues.
Navigating the World Wide Web
Accessing a web page, such as https://hackett.io, initially involves a query to a DNS server. The server translates the host portion (hackett) in combination with the Top Level Domain (io) of the URL into an IP address, such as 214.125.239.118. In all web requests, your computer and browser transmit their type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
The default gateway is typically an auto-configured address provided via DHCP. The default gateway, such as 192.0.0.156 (usually ending in .1 or .254 depending upon the scope size), is the point to which your computer forwards all its traffic for routing. For IPv6, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/. Users can also check on 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 192.0.0.156 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 fe80:6eff:4249:cb45:2d86%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): {18.156.85.55, 226.48.233.186}
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 d5:a8:87:3c:97:8a
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 7d:fa:69:77:fe:43
}
Solutions for Addressing Connectivity Issues
When it comes to transferring 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.
Troubleshooting Techniques for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are utilizing - be it 10.12.2, 11.5.7, or 12.2.5, there is a wide array of tools available for addressing connectivity issues. However, these manual actions and scripts do not offer a set of interconnected values over time. This is where automated remote troubleshooting becomes essential, especially for teams that have adopted remote work and Work From Anywhere (WFA) policies.
Utilizing Built-in Scripts for Assistance
An invaluable tool for OSX/macOS users is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool offers a more comprehensive range of logs (albeit many are point-in-time with regards to wireless, similar to wdutil).
To run sysdiagnose in the background and generate logs at /var/tmp/<blah>.tar.gz, the command sudo nohup /usr/bin/sysdiagnose -u & can be used. Alternatively, for an interactive (albeit minimal interaction) experience, you can run sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. If not run in the background, it should open Finder in the correct location, allowing you to navigate to /var/tmp or use Finder with Cmd+Shift+G to direct Finder to the path. It’s worth noting that the file sizes are approximately 300MB.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
