How Do You Check Wifi Issues
The Mechanics of Internet Addressing
When it comes to the Internet, you might be assigned a Public IPv4 address such as 20.125.243.97 or an IPv6 address like 2000:c5b4:501a:e669:11f6:d827:7f2:9d54. You can verify this by visiting https://test-ipv6.com/. However, attempting to convey these addresses to individuals who are not well-versed in technology, or even mentioning MAC addresses like 7f:86:c7:57:e8:68, can quickly become error-prone and complex. Moreover, this approach does not provide any historical data, especially when it comes to past issues.
Navigating the World Wide Web
When you attempt to access a website like https://stehr.biz, you first reach out to a DNS server to transform the host portion (stehr) in combination with the Top Level Domain (biz) of the URL into an IP address, such as 255.214.193.83. Furthermore, your computer and browser share their type with every web request, for example: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Understanding the Significance of Default Gateways
Your default gateway is typically an address that is automatically configured via DHCP. You receive a default gateway, for instance 172.18.215.201 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer forwards all its traffic to be routed further. For IPv6, we provide an in-depth explanation in our how-to-fix-ipv6-connectivity/ article, but on Mac or Linux, you can check it 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 172.18.215.201 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 fe80:99ec:3883:7149:960%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): {250.99.137.181, 184.144.110.146}
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 7f:86:c7:57:e8:68
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 06:5b:b2:1b:ce:e2
}
Fixing Connectivity Issues in Wired and Wireless Networks
When it comes to transmitting data to your router, the choice of using a wired or wireless (Wi-Fi) medium is crucial at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX
Regardless of the version of OSX/macOS you are currently using, whether it’s 10.11.9, 11.3.6, or 12.0.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting proves to be extremely beneficial, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One of the most useful tools on OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI. This tool 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 most of it is only relevant to wireless settings, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background, which will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose but be aware of the privacy warning. Running it in the background should open Finder in the correct location, and you can also navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the files. Just keep in mind that the file sizes can be around 300MB or more.
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