How Do You Support OSX IP Settings
Explanation of Internet Addressing
When using the Internet, you receive a Public IPv4 address, such as 217.165.130.63, or an IPv6 address, such as 2000:3c6d:880e:bf4d:c9d8:e5d9:c8f9:b52a. You can verify this by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or MAC addresses, like 61:3f:18:90:5b:ae, can be prone to errors and quickly become complicated. Moreover, it does not provide any historical data, especially when historical issues arise.
Navigating the Internet
To visit a webpage, such as https://beatty.biz, you start by accessing a DNS server to convert the host portion (beatty) combined with the Top Level Domain (biz) of the URL into an IP address, for example, 139.5.148.235. Your computer and browser also transmit their type with all web requests, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
The Significance of Default Gateways
Typically, your default gateway is an address configured automatically via DHCP. You receive a default gateway, such as 192.168.175.236 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be forwarded. For IPv6, we provide an in-depth guide on how-to-fix-ipv6-connectivity/, but you can check it on Mac or Linux 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 192.168.175.236 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:c048:d0da:7367:7857%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): {94.121.192.45, 142.26.72.176}
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 61:3f:18:90:5b:ae
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 28:14:d3:96:4f:af
}
Troubleshooting Connectivity Issues
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Resolving Connection Problems on Apple Devices
Regardless of whether you are running MacOS or OSX version 10.14.9, 11.0.9, or 12.1.7, there are various tools available for troubleshooting. However, these manual methods and scripts do not provide a continuous stream of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for remote work and Work From Anywhere (WFA) situations.
Utilizing In-Built Scripts for Assistance
An extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to produce a wide range of logs (although many are only relevant to wireless at a specific point in time, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (even though there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose, which will trigger 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. Keep in mind that the file sizes are typically around 300MB.
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