How To Troubleshoot Common Wifi Internet Issues
Understanding IP Address Assignment
When using the Internet, you are assigned a specific IP address like 199.16.130.245 (IPv4) or 2000:e802:d6e2:b4ec:8021:e76e:85e3:f8d4 (IPv6). Verifying your IP address can be done through the website https://test-ipv6.com/. However, for those who are not well-versed in technology, communicating these addresses or even referencing MAC addresses like 6b:83:31:83:69:05 can become complicated and prone to errors. Additionally, this method does not provide any historical data, particularly regarding past issues.
Navigating the Internet
To access a website such as https://ernser-koepp.com, you first connect to a DNS server to translate the host portion (ernser-koepp) combined with the Top Level Domain (com) of the URL into an IP address, such as 106.250.218.162. Every web request made by your computer and browser contains information about its type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Your default gateway is usually an address that is automatically configured through DHCP. You are given a default gateway such as 10.247.147.134 (commonly ending in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For IPv6, a detailed explanation can be found in how-to-fix-ipv6-connectivity/, but on Mac or Linux, you can check this using the following command:
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 10.247.147.134 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 fe80:9378:f753:58c4:bfce%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): {248.117.107.18, 22.191.46.171}
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 6b:83:31:83:69:05
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 86:7b:25:6a:5b:8d
}
Fixing Issues with Wired and Wireless Connections
When it comes to your network connection, whether wired or wireless (Wi-Fi), troubleshooting can be a challenge especially at the physical and data layer when sending data to your router.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of the version of OSX/macOS you’re using, whether it’s 10.15.8, 11.3.3, or 12.2.9, there is a variety of tools available for troubleshooting. However, these tools often fail to provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams that have embraced remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings and can also be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to a specific point in time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively (although there isn’t much interaction), 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 or use Finder with Cmd+Shift+G to locate the path. However, be mindful of the file sizes, which can be around 300MB.
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