How To Support Common Wifi Router Issues
Understanding Internet Addressing
In the realm of the Internet, individuals are typically assigned a Public IPv4 or IPv6 address, such as 64.51.99.140 or 2000:5d2:3553:65f6:5c55:d7dc:29a1:3ff8. This information can be verified at https://test-ipv6.com/. However, conveying these addresses, along with MAC addresses like b2:6d:20:05:15:7c, to those without technical expertise can be quite challenging and prone to errors. In addition, it lacks historical data, which could be beneficial when troubleshooting past issues.
Navigating the World Wide Web
When attempting to visit a website such as https://farrell.biz, the initial step involves accessing a DNS server to convert the URL’s host portion (farrell) and the Top Level Domain (biz) to an IP address, for example, 95.158.57.47. Furthermore, when making web requests, the computer and browser transmit information about its type, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko.
Significance of Default Gateways
Typically obtained automatically through DHCP, the default gateway (e.g., 192.0.0.38 - often ending in .1 or .254 based on the scale) is where a computer forwards all of its traffic for routing. For IPv6 connectivity, a detailed guide is available at how-to-fix-ipv6-connectivity/, with instructions for Mac and Linux systems including:
// code snippet here
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 192.0.0.38 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 fe80:19d:256b:76d5:f13d%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): {85.200.187.215, 20.105.10.201}
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 b2:6d:20:05:15:7c
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 2b:e4:f5:fc:3c:9a
}
Fixing Connectivity Issues in Wired and Wireless Networks
When it comes to transmitting data to your router, you may be using a physical wired connection or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are running OSX/macOS version 10.12.1, 11.6.1, or 12.0.5, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. Automated remote troubleshooting becomes particularly useful, especially for teams adopting remote work and Work From Anywhere (WFA).
Handy Built-in Scripts
A useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which can generate a wide range of logs, although many of them are only relevant at a specific point in time in relation to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, if you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which will display 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. Keep in mind that the file sizes are around 300MB more or less.
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