How Do You DiagnOSe Common Wifi Internet Issues
Understanding Internet Addressing
When using the Internet, you are assigned an IP address, which can be a Public IPv4 address such as 253.169.138.53 or an IPv6 address like 2000:9289:181:9b8e:cc67:334b:8be1:8089. You can verify your address at https://test-ipv6.com/. However, conveying these alphanumeric addresses, or even MAC addresses like 8f:65:a2:39:46:d4, to individuals who are not tech-savvy can be prone to error and quickly becomes complex. Furthermore, this method does not provide any historical data, particularly from past incidents.
Navigating the Web
When attempting to access a website like https://schowalter.co, the initial step involves contacting a DNS server to convert the combination of the host portion (schowalter) and the Top Level Domain (co) of the URL into an IP address, such as 167.236.250.211. Every web request from your computer and browser includes its type, for example Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
The Significance of Default Gateways
Your default gateway is typically an address that is automatically configured through DHCP. This gateway address, such as 172.29.112.19 (commonly ending in .1 or .254 depending on the scope size), is where your computer directs all its traffic to be routed onward. For IPv6, you can find a detailed guide on how-to-fix-ipv6-connectivity/ or check on Mac or Linux 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 172.29.112.19 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 fe80:523d:f50d:6abb:364f%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): {76.207.232.224, 1.229.107.20}
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 8f:65:a2:39:46:d4
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 4a:4c:d7:64:2b:46
}
Resolve Connectivity Issues - Wired vs. Wireless
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you are running - whether it’s 10.15.4, 11.6.7, or 12.3.3 - there are various tools available for troubleshooting. However, these tools do not provide a set of correlated values over time, which is where automated remote troubleshooting becomes valuable, particularly for teams that embrace remote work and Work From Anywhere (WFA).
Utilizing Pre-Built Scripts
One useful tool on OSX/macOS is sudo wdutil info, 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 relevant to wireless at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and generate logs in /var/tmp/<blah>.tar.gz. For interactive use, you can run sudo /usr/bin/sysdiagnose and it will provide a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Cmd+Shift+G in Finder. Be mindful of the file sizes, which are typically around 300MB.
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