Test Wifi Router Issues
How Addressing Works on the World Wide Web
When using the Internet, you might be assigned a Public IPv4 address such as 195.125.2.109 or an IPv6 address like 2000:e379:41d9:c70b:6739:3807:ece1:6888. Verification for this can be done via https://test-ipv6.com/. However, conveying and using these addresses, or even identifying MAC addresses like 0a:bc:d2:f9:be:f0 can be prone to errors and complexity. Moreover, it does not provide any historical data, especially related to past issues.
How the Internet Facilitates Web Access
To access a web page like https://shields.name, the first step is to contact a DNS server which translates the host portion (shields) combined with the Top Level Domain (name) of the URL into an IP address such as 44.153.7.69. Each web request from your computer and browser includes information about its type, for example: 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
Normally configured address via DHCP, your default gateway is responsible for assigning an address such as 192.0.0.129 (commonly ends in .1 or .254 based on the scope size) which is the destination where your computer sends all its traffic to be routed onwards. For IPv6, an in-depth guide is available at how-to-fix-ipv6-connectivity/ and checking on Mac or Linux is possible 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 192.0.0.129 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:f43c:971d:6e4e:a971%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): {214.82.105.135, 157.42.28.48}
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 0a:bc:d2:f9:be:f0
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 d6:d1:b3:8e:5e:a5
}
Fixing Connectivity Issues with Your Network
When it comes to transmitting data to your router, you may encounter problems with your wired or wireless (Wi-Fi) connection at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX/macOS versions such as 10.11.1, 11.1.4, or 12.0.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where the importance of automated remote troubleshooting comes into play, especially for teams that are remote or practice Work From Anywhere (WFA).
Utilizing Built-in Tools to Resolve Issues
A useful tool for OSX/macOS users is the sudo wdutil info command, which can provide a dump of current wireless settings through the CLI 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 many are only relevant to wireless settings at a specific point in time, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, use the command: sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, use the command: sudo /usr/bin/sysdiagnose. This will provide a privacy warning and open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes can be around 300MB or slightly more.
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