Understand Wifi Connectivity
The Functioning of Internet Addressing
When navigating the Internet, you may be assigned a Public IPv4 address such as 33.175.66.141 or an IPv6 address like 2000:65eb:7723:1024:fd5a:31cd:2844:b8c3. You can verify this information by visiting https://test-ipv6.com/. However, explaining or relaying these addresses, along with MAC addresses like 0e:93:34:b1:c4:e2, can be prone to errors and can become complex. Furthermore, this method does not provide any historical data, particularly in the event of past issues.
Navigating the Internet
To access a website like https://lynch-blick.name, your initial step is to contact a DNS server in order to convert the host portion (lynch-blick) combined with the Top Level Domain (name) of the URL into an IP address such as 224.88.240.188. Every time you make a web request, your computer and browser also send its type, such as Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Typically, your default gateway is an automatically configured address through DHCP. Your computer receives a default gateway like 192.0.0.244 (usually ending in .1 or .254 based on the size of the scope), which serves as the point where your computer forwards all its traffic for further routing. For IPv6, we provide an in-depth exploration in how-to-fix-ipv6-connectivity/, but you can verify this on a Mac or Linux system 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 192.0.0.244 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 fe80:752c:2847:c332:f3ea%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): {194.206.86.205, 157.104.65.210}
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 0e:93:34:b1:c4:e2
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 ab:85:d2:a5:31:ce
}
Resolve Issues with Wired and Wireless Connections
When it comes to transferring data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Irrespective of whether you are running OSX/macOS version 10.11.2, 11.1.3, or 12.1.4, there are various tools available for resolving issues. However, these manual actions and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting proves to be particularly useful, especially for teams that adhere to remote work and Work From Anywhere (WFA) practices.
Useful Built-in Scripts
A highly beneficial tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI, and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool can be utilized to produce a wide range of logs, although much of it pertains to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose, which will issue 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 mindful of the file sizes, which are typically around 300MB.
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