Check Wifi Router Issues
Demystifying Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 217.155.14.160, or an IPv6 address, like 2000:f6df:c052:71bb:e0fc:8e29:74d4:4e2d. The verification of these addresses can be done via https://test-ipv6.com/. However, for those who are not technologically inclined, conveying or even identifying MAC addresses, such as d3:22:54:eb:11:6e, can quickly become complicated and prone to errors. Furthermore, this method does not provide any historical data, especially when it comes to past issues.
Navigating the World Wide Web
When attempting to access a web page, such as https://raynor.net, the first step is to contact a DNS server in order to convert the host part (raynor) along with the Top Level Domain (net) of the URL into an IP address, like 216.232.252.169. Every web request from your computer and browser includes its type, such as Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.
Understanding the Significance of Default Gateways
The default gateway is typically an address configured automatically through DHCP. It usually ends in .1 or .254, depending on the scope size, and is where your computer directs all traffic to be routed onwards. For a detailed guide on IPv6, you can refer to how-to-fix-ipv6-connectivity/. If you are using Mac or Linux, a check can be performed 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 172.21.60.179 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 fe80:5c43:f8eb:a55f:a9a3%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): {106.254.39.111, 90.85.128.255}
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 d3:22:54:eb:11:6e
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 34:9b:ae:3d:20:15
}
Fixing Connectivity Issues for Wired and Wireless Networks
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 Steps for Apple macOS / OSX
No matter which version of OSX/macOS you’re operating on - whether it’s 10.11.1, 11.0.3, or 12.1.2, there are several tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams that adopt remote work and Work From Anywhere (WFA) practices.
Utilizing Pre-installed Scripts
One of the useful tools on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose tool, which can generate a variety of logs, although many are only relevant to wireless at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, but be mindful of the large file sizes of about 300MB more or less.
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