How To Understand Apple Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a public IP address, which can either be in the IPv4 format like 117.119.64.67, or in the IPv6 format like 2000:3670:50ff:2c1c:1fb2:c21b:5136:3eaf. You can verify your assigned address at https://test-ipv6.com/. However, it can be challenging for non-technical individuals to communicate or identify these addresses, including MAC addresses like 84:72:b5:32:f1:30. Furthermore, this method does not provide historical data on past issues.
Navigating the World Wide Web
To reach a website such as https://prohaska.org, you initially connect to a DNS server to convert the host portion (prohaska) along with the Top Level Domain (org) of the URL into an IP address, such as 219.43.175.96. Your computer and browser also include specific type information with all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. This gateway, such as 192.168.165.37 (usually ending in .1 or .254), is where your computer forwards all its traffic to be routed to other destinations. For IPv6, detailed information on troubleshooting connectivity can be found at how-to-fix-ipv6-connectivity/, and can be checked on Mac or Linux 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 192.168.165.37 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:a8de:3edf:96aa:7a13%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): {244.188.127.173, 6.161.172.14}
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 84:72:b5:32:f1:30
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 4a:f2:0d:9b:0b:6e
}
Dealing with Issues in Wired and Wireless Connections
Whether you are using a wired or wireless (Wi-Fi) medium at the physical and data layer to transmit data to your router, troubleshooting can be a crucial task.
Troubleshooting Tips for Apple macOS / OSX Users
Irrespective of the version of OSX/macOS you are running, such as 10.13.7, 11.1.4, or 12.2.9, there exists a variety of tools to resolve issues. However, the existing manual interventions and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting becomes particularly valuable, especially for teams that endorse remote work and Work From Anywhere (WFA).
Useful Built-in Tools for Troubleshooting
One notable tool on OSX/macOS is sudo wdutil info, which produces a dump to the CLI of current wireless settings and can be configured to generate specific logs for troubleshooting. Moreover, the sysdiagnose tool offers a more comprehensive approach by generating a wide array of logs, although much of it is only pertinent to wireless settings like wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, the tool can be executed in the background and will write logs to /var/tmp/<blah>.tar.gz. For interactive use, you can runsudo /usr/bin/sysdiagnose and a privacy warning will be displayed. Running it this way should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be mindful of file sizes, which can be around 300MB more or less.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
