DiagnOSe Common Wifi Router Issues
Understanding Internet Addressing
When connected to the Internet, you are assigned a unique address, either in the form of Public IPv4 like 223.170.172.240 or an IPv6 address like 2000:f204:ba10:9459:9f9c:1476:132f:4ab7. You can verify your assigned address at https://test-ipv6.com/. However, the complexity of communicating these addresses, as well as MAC addresses like 06:e7:a5:db:34:85, poses a challenge, particularly for those who are not technically inclined. Moreover, historical data cannot be obtained easily, especially pertaining to past issues.
Navigating the World Wide Web
Accessing a website such as https://ratke.io requires you to first contact a DNS server to convert the host portion (ratke) combined with the Top Level Domain (io) of the URL into an IP address like 5.87.11.46. With each web request, your computer and browser also transmit information about its type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
The Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. This gateway, such as 192.0.0.76 (although it usually ends in .1 or .254, depending on the scope size), is where your computer forwards all its traffic to be routed further. For IPv6, a detailed explanation is available at how-to-fix-ipv6-connectivity/, and you can perform checks on Mac or Linux with the following command:
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 192.0.0.76 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 fe80:4d11:6942:1640:ddca%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): {157.172.136.186, 146.3.112.250}
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 06:e7:a5:db:34:85
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 29:e6:e4:4c:2b:58
}
Solutions for Resolving Issues with Wired and Wireless Connections
When transferring data to your router, you may utilize either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Efficient Measures for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are operating on - be it 10.11.4, 11.0.3, or 12.3.8 - there exists a variety of tools to address troubleshooting issues. However, these manual actions and scripts fail to provide a sequence of correlated values over a period of time. This is where automated remote troubleshooting becomes crucial, particularly for teams that have adopted remote work and the Work From Anywhere (WFA) concept.
Effective Built-in Scripts That Offer Assistance
An extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a comprehensive dump of current wireless settings to the CLI, and can also be configured to generate specific troubleshooting logs. Furthermore, a more extensive tool, sysdiagnose, can be utilized to generate a wide range of logs (although much of it is only relevant to wireless at a specific moment, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background, writing logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute sudo /usr/bin/sysdiagnose, which will display a privacy warning. If 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. Just keep in mind that the file sizes are approximately 300MB or so.
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