How Can I DiagnOSe Common Wifi Internet Issues
Understanding Internet Addressing
When connected to the Internet, your device is assigned a unique Public IPv4 address, such as 186.18.86.206, or an IPv6 address, like 2000:bbc6:dd29:5bca:af44:953c:a931:3424. You can verify this information using https://test-ipv6.com/. However, conveying these addresses to individuals unfamiliar with technical jargon, along with MAC addresses like ea:15:6a:62:2a:b9, can be error-prone and quickly become complex. Furthermore, this method does not provide historical data, especially when past issues arise.
Navigating the Web
Accessing a website such as https://wintheiser.name involves initially reaching out to a DNS server to convert the host portion (wintheiser) combined with the Top Level Domain (name) of the URL to an IP address, such as 65.180.33.207. When making web requests, your computer and browser send their 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
Typically, your default gateway is automatically configured through DHCP and appears as an address like 192.168.29.55 (usually ending in .1 or .254, depending on the scope size). This is where your computer directs all its traffic to be routed further. For IPv6, you can find detailed information in our article how-to-fix-ipv6-connectivity/ or by checking on Mac or Linux with:
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 192.168.29.55 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 fe80:80c7:fdf8:f6c8:1223%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): {232.89.43.207, 36.78.30.190}
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 ea:15:6a:62:2a:b9
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 c4:a7:6d:65:76:11
}
Fixing Connectivity Issues: Wired vs. Wireless
When it comes to sending data to your router, you have the option of using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are running OSX/macOS versions like 10.11.8, 11.2.4, or 12.1.2, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time, making automated remote troubleshooting especially valuable for teams embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
A very useful tool on OSX/macOS is sudo wdutil info, which dumps current wireless related settings to the CLI and can be set up to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, though many are only relevant to wireless at a specific point in time, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz, or to run it interactively with a privacy warning using sudo /usr/bin/sysdiagnose, can be helpful. Just be mindful of the file sizes, which are typically around 300MB.
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