Support Mac Internet Connection
Understanding Internet Addressing
When using the Internet, you are assigned a unique public IP address. This could be an IPv4 address like 25.227.191.140 or an IPv6 address like 2000:bf63:1df4:240:5a9b:e582:a04a:7d73. To verify your IP addresses, you can visit https://test-ipv6.com/. However, conveying and understanding these addresses, as well as MAC addresses like 55:a7:90:9b:ce:4c, can be challenging for non-technical individuals, especially without historical data.
Navigating the Internet
When accessing a website such as https://gislason.org, your computer initially contacts a DNS server to translate the URL’s host (gislason) and Top Level Domain (org) to an IP address, such as 31.50.149.239. Furthermore, your computer and browser send their specifications with each web request, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
Understanding the Significance of Default Gateways
The default gateway, usually assigned through DHCP, serves as the routing point for all outbound traffic from your computer. It is typically assigned an address like 172.28.163.190 (often ending in .1 or .254 based on the scope size). More detailed information on configuring default gateways for IPv6 can be found in our article on how-to-fix-ipv6-connectivity/. For Mac or Linux, this can be verified using the following command.
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 172.28.163.190 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 fe80:15a:e175:7273:986d%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): {21.182.2.126, 252.226.93.107}
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 55:a7:90:9b:ce:4c
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 15:c5:f1:e1:44:c9
}
Resolving Connection Issues with Wired or Wireless Networks
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Apple macOS / OSX Troubleshooting
Regardless of whether you are running OSX/macOS 10.12.4, 11.5.9, or 12.3.2, there are various troubleshooting tools available. However, these manual actions and scripts lack the ability to provide a series of correlated values over time. This is where automated remote troubleshooting proves to be especially beneficial for teams that practice 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 of the current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool offers a more comprehensive approach to generating a wide range of logs, although much of it is only relevant to the wireless settings at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and save the logs to /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 and it will give a privacy warning. When not run in the background, the file should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Be mindful that the file sizes are approximately 300MB.
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