How Can I Support Mac Internet
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 239.29.222.239, or an IPv6 address, like 2000:e720:6b4:421:4222:8b03:9ac0:b073. You can verify this information by visiting https://test-ipv6.com/. However, the process of communicating these addresses, or even referencing MAC addresses such as 1f:93:32:05:82:dd, can be prone to errors and becomes complex rather quickly. In addition, this method lacks historical data, particularly when facing previously encountered issues.
Navigating the Online World
When attempting to reach a website, like https://cremin.info, you first access a DNS server to translate the host portion (cremin) combined with the Top Level Domain (info) of the URL into an IP address, like 166.133.82.220. Furthermore, your computer and browser send their type with all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Your default gateway is typically an address assigned automatically via DHCP. For instance, you might receive a default gateway like 172.23.146.173 (commonly ending in .1 or .254 based on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, we offer an in-depth examination in our article on how-to-fix-ipv6-connectivity/, but you can also verify this on Mac or Linux 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 172.23.146.173 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 fe80:1736:78d5:4c17:a534%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): {164.75.87.158, 151.193.120.148}
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 1f:93:32:05:82:dd
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 4e:db:dd:61:d7:06
}
Solve Issues with Wired and Wireless Connections
When it comes to transmitting 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 are running, whether it’s 10.13.4, 11.2.9, or 12.1.8, there are a variety of tools available to help solve connectivity issues. However, these tools do not provide a series of correlated values over time like automated remote troubleshooting does, which is especially useful for teams that work remotely or embrace Work From Anywhere (WFA).
Handy Built-in Scripts
One useful tool for OSX/macOS users is the sudo wdutil info command, 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 particular point in time, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For interactive use, you can run sudo /usr/bin/sysdiagnose (although there is not much interaction) and it will give a privacy warning. If 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 around 300MB more or less.
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