How To DiagnOSe Apple Internet
Understanding the Functionality of Internet Addressing
When using the Internet, it is possible to have either a Public IPv4 address, such as 94.68.16.86, or an IPv6 address, like 2000:73f3:924f:d854:3a0a:88b2:5f4b:701c. You can verify your address by visiting https://test-ipv6.com/. However, for those who are not technically savvy, conveying these addresses or referring to MAC addresses, such as c3:25:c8:c1:5b:29, can be prone to error and become complex. Moreover, this method does not offer historical data, particularly regarding past issues.
Navigating the World Wide Web
When attempting to access a website, such as https://gibson.co, the first step is to access a DNS server, which will translate the host portion (gibson) combined with the Top Level Domain (co) of the URL into an IP address, such as 105.179.179.207. Additionally, your computer and browser transmit their type with all web requests, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
The default gateway is typically an automatically configured address via DHCP, such as 192.0.0.75 (although they generally end in .1 or .254 depending on the scope size). This is the location where your computer directs all of its traffic to be routed. For IPv6, more in-depth information can be found at how-to-fix-ipv6-connectivity/, or you can perform a check on a Mac or Linux using:
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 192.0.0.75 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 fe80:177a:e63d:2c7a:d49d%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): {195.112.24.213, 147.212.224.29}
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 c3:25:c8:c1:5b:29
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 0a:7d:a0:c6:32:69
}
Addressing Issues with Wired and Wireless Connections
When it comes to transmitting data at the physical and data layer, you have the option of using either a wired or wireless (Wi-Fi) medium to send the data to your router.
Fixing Problems on Apple macOS / OSX Devices
No matter which version of OSX/macOS you are operating, whether it’s 10.14.7, 11.3.7, or 12.3.3, there are a variety of tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting comes in handy, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of the current wireless settings and can be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is specific to a point in time in relation to wireless, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be mindful of the large file sizes of about 300MB.
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