Understand Wifi Router Issues
Understanding Internet Addressing Systems
When it comes to the Internet, you are assigned a unique Public IPv4 address, such as 165.22.231.238, or an IPv6 address, like 2000:9a97:3831:9cf2:bcb2:29b4:113:6967. You can verify your address at https://test-ipv6.com/. However, communicating these addresses, or even referencing MAC addresses like 26:e8:0f:d8:1c:c0, can be prone to errors and become complicated, especially for those without a strong technical background. Moreover, this method does not provide any historical data, particularly for past issues.
Navigating the World Wide Web
When trying to access a webpage such as https://sauer-turner.info, your computer initially contacts a DNS server to translate the host portion (sauer-turner) combined with the Top Level Domain (info) of the URL into an IP address, for example, 227.116.55.95. In fact, your computer and browser attach identifying information to all web requests, such as Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16.
The Significance of Default Gateways
Normally, your default gateway is an address that is automatically configured via DHCP, such as 172.19.1.9 (although they typically end in .1 or .254, depending on the scope size). This is the point where your computer directs all its traffic to be routed onwards. For IPv6, in-depth guidance can be found at how-to-fix-ipv6-connectivity/, but you can also verify this 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 172.19.1.9 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:d8ff:37c6:4b21:2078%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): {187.115.242.115, 190.101.11.2}
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 26:e8:0f:d8:1c:c0
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 46:20:46:63:ae:c1
}
Solutions for Wired and Wireless Connection Issues
When it comes to transmitting data to your router, you may encounter connectivity issues with both wired and wireless (Wi-Fi) mediums at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are using OSX or macOS versions such as 10.11.6, 11.0.6, or 12.3.7, there are various troubleshooting tools available. However, these tools only provide isolated data and lack the ability to generate correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams engaged in remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
On OSX/macOS, the sudo wdutil info tool is quite handy as it provides a dump of current wireless settings in the CLI and can be set up to generate specific logs for troubleshooting. Additionally, the more comprehensive sysdiagnose tool can be utilized to generate a wide range of logs, although many of them are only relevant 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 for you. For an interactive option, you can run sudo /usr/bin/sysdiagnose which will provide a privacy warning. If it’s 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 or by manually entering the path. Keep in mind that the file sizes are approximately 300MB.
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