Support Apple Internet Connection
Explanation of Internet Addressing
When using the Internet, you can obtain a Public IPv4 address such as 159.95.223.220 or an IPv6 address like 2000:eb04:5856:e9e4:e4cf:5291:d1a4:bde9. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not technically inclined, conveying these addresses, or even specifying MAC addresses like c2:8e:f7:af:73:b1, can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially when previous issues occurred.
Navigating the Internet
To access a web page such as https://reilly.net, you first contact a DNS server to convert the host portion (reilly) combined with the Top Level Domain (net) of the URL to an IP address like 182.38.115.51. Your computer and browser include their type in all web requests, 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
Your default gateway is typically an address configured automatically via DHCP. This gateway, usually ending in .1 or .254 depending on the scope size, such as 192.0.0.55, is where your computer sends all its traffic to be routed onwards. An in-depth discussion on IPv6 can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this by 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 192.0.0.55 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 fe80:6d3:f4f7:1005:43cb%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): {118.173.29.87, 56.104.223.64}
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 c2:8e:f7:af:73:b1
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 1b:42:40:6d:c1:e2
}
Resolve Issues with Wired or Wireless Connections
When it comes to transferring data to your router, you might be using either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Methods for Apple macOS / OSX
No matter which version of OSX/macOS you’re working with - whether it’s 10.14.8, 11.3.6, or 12.0.2 - there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for teams that operate remotely and embrace a Work From Anywhere (WFA) approach.
Useful Built-in Scripts
One useful tool for troubleshooting on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. In addition, the sysdiagnose tool can be used to generate a wide range of logs, though many of these are only relevant to wireless issues, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute this tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there isn’t much interaction involved), you can use the command sudo /usr/bin/sysdiagnose, which will display 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. However, be aware that the file sizes can be approximately 300MB.
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