Troubleshoot Wifi Issues
Understanding Internet Addressing
When using the Internet, your device may be assigned a Public IPv4 address such as 32.181.224.18 or an IPv6 address like 2000:bd3:282e:c2ce:d569:88a8:88ac:369b. You can verify this at https://test-ipv6.com/. However, conveying these addresses to individuals who are not technologically inclined, or even referencing MAC addresses like 74:7c:27:d2:38:14, can be prone to errors and becomes complex quickly. Furthermore, it does not provide any historical data, especially when dealing with past issues.
Navigating the Web
In order to access a website such as https://bins.com, you initially contact a DNS server to convert the host portion (bins) and the Top Level Domain (com) of the URL into an IP address, like 183.51.185.132. Your computer and browser specifically send its type with all web requests e.g. Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
The Significance of Default Gateways
Usually, your default gateway is an address that is automatically configured via DHCP. You receive a default gateway, such as 192.168.49.122 (although they typically end in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, you can find detailed instructions on how-to-fix-ipv6-connectivity/. Additionally, you can check on Mac or Linux with:
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 192.168.49.122 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 fe80:8d0a:9f2d:92f6:c92e%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): {204.60.222.249, 236.225.85.203}
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 74:7c:27:d2:38:14
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 db:5c:9f:52:ee:8d
}
Fixing Connectivity Issues for Wired and Wireless Networks
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you’re using, whether it’s 10.14.3, 11.0.9, or 12.2.8, there are a variety 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 valuable, especially for teams that endorse remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very 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. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of the logs are point-in-time only in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will run it in the background and write logs to /var/tmp/<blah>.tar.gz. To run it interactively, you can run sudo /usr/bin/sysdiagnose and it will give a privacy warning. When 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. However, be aware of the file sizes, which are around 300MB more or less.
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P.S. Tips For Remote Network and Client Support
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