How Can I Test OSX IP Settings
Understanding the Functioning of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 208.76.69.233or an IPv6 address like 2000:72b9:3cca:80e1:b4b7:8f2c:27c0:ffe3. This information can be verified at https://test-ipv6.com/. However, conveying these addresses, or even mentioning MAC addresses like 58:65:86:36:16:95, can be prone to mistakes and can become complex, especially for individuals not well-versed in technology. Furthermore, this method does not provide any historical data, particularly regarding past issues.
Navigating the Internet
In order to access a webpage such as https://schoen.biz, an initial step involves contacting a DNS server to convert the host portion (schoen) in combination with the Top Level Domain (biz) of the URL to an IP address, for instance, 52.180.5.184. In every web request, your computer and browser actually transmit its type, for example:
Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. Users are assigned a default gateway such as 10.103.99.20 (although they usually end in .1 or .254, depending on the scope size). This is the point where your computer directs all its traffic to be routed further. For those interested in more details about setting up IPv6 connectivity, a detailed article is available at how-to-fix-ipv6-connectivity/. On Mac or Linux, this information can be verified by using the following 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 10.103.99.20 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 fe80:9f34:f97b:531d:27a5%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): {81.58.103.60, 226.10.255.221}
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 58:65:86:36:16:95
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 ab:97:87:43:28:f9
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to transmitting data, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layers to send the information to your router.
Resolving Problems on Apple macOS / OSX Devices
Regardless of the version of OSX/macOS you are running, whether it’s 10.11.3, 11.3.4, or 12.0.7, there are various troubleshooting tools available. However, these manual methods and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts for Assistance
One particularly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless-related settings to the Command Line Interface (CLI) and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to produce a wide range of logs, although much of it is relevant only at a specific point in time in relation to wireless, similar to wdutil.
To run it in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive (albeit limited interaction) session, you can runsudo /usr/bin/sysdiagnose, which 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. Just be aware that the file sizes are approximately 300MB, give or take.
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