How Can I Fix Common Wifi Router Issues
Understanding Internet Addressing
When using the Internet, you may have a Public IPv4 address such as 239.58.7.64 or an IPv6 address like 2000:6d7f:e9c2:ebaa:475:e075:cee1:1155. This information can be verified at https://test-ipv6.com/. However, for individuals who are not tech-savvy, communicating these addresses or even referencing MAC addresses like ab:ac:52:9f:ad:40 can be prone to errors and become complex. Furthermore, this does not provide any historical data, especially when addressing past issues.
Navigating the World Wide Web
When attempting to access a web page such as https://cummings.name, the initial step involves connecting to a DNS server to convert the host portion (cummings) along with the Top Level Domain (name) of the URL into an IP address, such as 121.192.166.181. Your computer and browser always sends its type with every web request e.g. Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured via DHCP. This default gateway, such as 172.20.214.46 (although they often end in .1 or .254 depending on the scope size), is where your computer routes all of its traffic. For IPv6, more detailed information can be found at how-to-fix-ipv6-connectivity/, and it can be checked 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 172.20.214.46 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:a62a:8ee2:d002:f4b4%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): {70.212.149.78, 159.90.22.114}
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 ab:ac:52:9f:ad:40
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 5b:d7:d2:43:95:a5
}
Resolving Wired and Wireless Connectivity Issues
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 layers.
Tips for Troubleshooting on Apple macOS / OSX
Regardless of whether you are running OSX/macOS 10.14.7, 11.5.8, or 12.1.2, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes especially valuable, particularly for teams that have adopted remote work or a Work From Anywhere (WFA) policy.
Useful Built-in Scripts
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can generate a wide range of logs, although many of them are only point-in-time related to wireless, much like 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 sudo /usr/bin/sysdiagnose, but be cautious of the file sizes, which are typically around 300MB.
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