How Can I Support Mac Internet Connection
Understanding the Function of Internet Addressing
When using the Internet, users may be assigned a Public IPv4 address, such as 174.150.115.224, or an IPv6 address like 2000:e385:3eb1:fdfd:5d02:2c55:4bf9:534d. This information can be verified at https://test-ipv6.com/. However, for individuals who are not well-versed in technology, the process of communicating these addresses, as well as MAC addresses like e9:cc:74:fb:bd:da, can become error-prone and complex. Furthermore, it does not provide any historical data, especially during past issues.
Navigating the World Wide Web
In order to access a website such as https://kling-yundt.org, the user initially communicates with a DNS server to convert the host portion (kling-yundt) in combination with the Top Level Domain (org) of the URL into an IP address, such as 118.204.74.187. When making web requests, the user’s computer and browser transmit their type, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285.
Understanding the Significance of Default Gateways
The default gateway is usually an address that is automatically configured through DHCP. Users receive a default gateway, such as 172.18.11.62 (although they usually end in .1 or .254 depending on the scope size), which serves as the place where the computer sends all of its traffic to be routed further. For IPv6, a detailed explanation can be found on how-to-fix-ipv6-connectivity/, and users can perform a check on 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 172.18.11.62 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 c1:7cdc:8ad3:59aa:a0d6:c0e1:e447:c644%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): {121.26.240.243, 235.10.34.222}
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 e9:cc:74:fb:bd:da
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 8d:5a:4d:64:85:f8
}
Diagnosing and Resolving Connectivity Issues
When it comes to transmitting data to your router, you may be using a physical wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you are using, whether it’s 10.13.7, 11.2.3, or 12.0.7, there are a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for remote work and Work From Anywhere (WFA) teams.
Useful Built-in Commands
A helpful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI, with the option to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless at a specific point in time, just like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. For an interactive experience (although there is limited interaction), you can run sudo /usr/bin/sysdiagnose, which will issue a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to specify the path. However, be cautious of the file sizes, which are generally around 300MB.
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