How Do You Troubleshoot Wifi Router Issues
An Overview of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 32.197.146.68 or an IPv6 address, such as 2000:e0f7:c22c:ef34:178c:77de:904e:5ca1. The status of these addresses can be verified at https://test-ipv6.com/. However, explaining these addresses to those who are not technically inclined, or identifying the MAC addresses like f7:97:46:5b:f9:5c, can become complex and prone to errors. Furthermore, this method does not provide historical data, particularly for past issues.
Navigating the World Wide Web
When attempting to access a website such as https://sipes-denesik.info, the first step is contacting a DNS server to convert the host part (sipes-denesik) along with the Top Level Domain (info) of the URL into an IP address, such as 89.52.78.181. In each web request, your computer and browser transmit information about their type, for instance: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
By default, the default gateway is an address that is automatically configured through DHCP. An example of a default gateway address would be 192.0.0.202 (commonly ending in .1 or .254, depending on the scope size). This is the point to which your computer sends all of its traffic to be routed. For IPv6, a more in-depth explanation can be found at how-to-fix-ipv6-connectivity/, or alternatively, it can be checked on Mac or Linux 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 192.0.0.202 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:e1d1:be7d:efc0:6116%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): {137.134.13.128, 188.47.209.181}
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 f7:97:46:5b:f9:5c
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 d4:65:3d:d5:dd:dc
}
Fixing Connectivity Issues for Wired or Wireless Networks
When transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.7, 11.4.8, or 12.3.2, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes invaluable, particularly for teams that are working remotely and embracing Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI 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 much of it is only point-in-time related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. Alternatively, if you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be aware that 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 locate the path. Keep in mind that the file sizes are approximately 300MB.
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