How To Fix Apple Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address such as 205.54.125.130 or an IPv6 address like 2000:7ca0:c6f3:ab07:f2e1:9fe:f2aa:50b7. You can verify this information by visiting https://test-ipv6.com/. However, for individuals without technical expertise, communicating these addresses, or even referencing MAC addresses like 74:bd:43:87:97:b8, can be error-prone and quickly become complex. Moreover, this method does not provide any historical data, especially when dealing with past issues.
Navigating the Internet
When trying to access a website, such as https://connelly.com, the process begins with contacting a DNS server to convert the host portion (connelly) and the Top Level Domain (com) of the URL into an IP address, like 144.252.156.90. Your computer and browser also include their specific types with all web requests, for example:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
The Significance of Default Gateways
The default gateway is typically an automatically configured address through DHCP. This gateway, such as 172.31.5.121 (commonly ending in .1 or .254 based on the scope size), serves as the destination for all the traffic sent from your computer to be routed onwards. For IPv6, more detailed instructions are available by following this link: how-to-fix-ipv6-connectivity/. Additionally, you can verify this information on Mac or Linux by using the command:
<br>
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 172.31.5.121 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 fe80:3457:8f3e:4ce6:a734%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): {100.202.246.124, 63.161.147.40}
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 74:bd:43:87:97:b8
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 e1:89:48:ff:8d:14
}
Resolve Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you have, whether it’s 10.15.3, 11.0.9, or 12.2.1, there are various 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 becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless related settings to the CLI and can also be configured 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 settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can 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, which will generate 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 approximately 300MB.
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