How To Test Common Wifi Internet Issues
Understanding IP Addresses
When connecting to the internet, you are assigned a Public IPv4 address such as 214.10.16.152 or an IPv6 address like 2000:7bb5:e514:1057:25a0:e0fa:8554:f00c. You can verify these addresses on https://test-ipv6.com/. However, for those who are not well-versed in technology, conveying these addresses, or even referencing MAC addresses like 59:80:aa:09:a3:84, can be prone to errors and become complicated fast. Furthermore, this method does not provide any historical data, particularly during previous issues.
A Guide to Navigating the World Wide Web
Accessing a website such as https://nikolaus.biz involves the initial step of reaching a DNS server to translate the host portion (nikolaus) combined with the Top Level Domain (biz) of the URL into an IP address like 163.93.195.58. With each web request, your computer and browser send their type, for instance: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding the Significance of Default Gateways
The default gateway is typically automatically assigned via DHCP. It is in the form of an address such as 10.19.115.118 (usually ending in .1 or .254 depending on the scope size) and serves as the point where your computer sends all its traffic to be routed onwards. For IPv6, one can refer to the detailed explanation provided in how-to-fix-ipv6-connectivity/ or check on Mac or Linux using the following code:
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 10.19.115.118 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 fe80:826e:5470:da38:522f%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): {235.183.21.62, 226.12.148.217}
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 59:80:aa:09:a3:84
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 e6:df:59:36:b4:a9
}
Resolving Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are currently using - whether it’s 10.15.4, 11.3.4, or 12.3.7 - there are various troubleshooting tools available. However, the manual actions and scripts may not provide a series of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that are embracing remote work and the idea of Working From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can 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 only pertains to wireless 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. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, although it will come with a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp. Keep in mind that the file sizes are approximately 300MB.
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