Support Mac Issues
An Overview of Internet Addressing
When connecting to the Internet, you are assigned a unique public IP address, such as the IPv4 address 17.175.235.27 or the IPv6 address 2000:334d:b6fa:e3cf:ae1:4427:33ff:5157. You can verify your assigned address at https://test-ipv6.com/. However, conveying these addresses and MAC Addresses like 3d:ff:68:93:ff:a2 can be challenging, especially for non-technical individuals. It also does not provide historical data on past issues.
Navigating the World Wide Web
When accessing a webpage, such as https://cummerata.co, your system reaches out to a DNS server to map the host (cummerata) and Top Level Domain (co) to an IP address, such as 238.248.20.6. Furthermore, your computer and browser send specific information along with web requests, like Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding the Significance of Default Gateways
By default, your system is assigned a gateway, typically through DHCP. This gateway, often ending in .1 or .254, serves as the central point for all outbound traffic. For IPv6, detailed instructions can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux systems, you can check this 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 192.0.0.82 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 fe80:42b7:4a5b:3e80:1f54%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): {235.1.55.44, 133.104.251.213}
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 3d:ff:68:93:ff:a2
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 bf:27:9c:51:fb:e9
}
Fixing Connectivity Issues in Wired or Wireless Networks
When it comes to the physical and data layer, you might be utilizing either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of the version of OSX/macOS you are running, whether it’s 10.15.4, 11.2.7, or 12.1.6, there is a wide range of 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 particularly useful, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A highly useful tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings, and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool offers a more comprehensive option for generating a variety of logs, even though much of it is specific to wireless settings just like wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and have it write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there is not much interaction), you can use sudo /usr/bin/sysdiagnose, which will provide a privacy warning. If 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 point Finder to the path. Keep in mind that the file sizes are approximately 300MB.
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