How Do You Check Common Wifi Router Issues
Understanding Internet Addressing
When you connect to the internet, your device is assigned a unique address, like 213.18.2.19 for IPv4 or 2000:3c9:6b2a:ac09:bf14:8e12:2733:5d0f for IPv6. You can verify this information at https://test-ipv6.com/. But translating these addresses for non-technical users or even referencing MAC addresses like ea:5f:b1:91:8f:c6 can be error-prone and complex, especially without historical data.
Navigating the World Wide Web
Accessing a website, such as https://block.org, involves initial communication with a DNS server to convert the website’s host (block) and Top Level Domain (org) to an IP address, like 0.56.44.69. Additionally, your computer and browser transmit information about themselves with each web request, such as Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36.
The Significance of Default Gateways
Default gateways are usually assigned automatically through DHCP and typically appear as addresses like 192.0.0.37, often ending in .1 or .254 depending on the scope size. All outbound traffic from your computer is directed to the default gateway, which then routes it further. For troubleshooting IPv6 connectivity on Mac or Linux, refer to how-to-fix-ipv6-connectivity/.
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 192.0.0.37 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 fe80:3014:4bc0:638d:5063%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): {255.44.109.54, 179.51.172.244}
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 ea:5f:b1:91:8f:c6
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 df:68:a3:03:a8:5d
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Solutions for Apple macOS / OSX
Regardless of the version of OSX/macOS you are using - whether it’s 10.15.5, 11.0.2, or 12.0.1, 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 invaluable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One of the helpful tools on OSX/macOS is sudo wdutil info, which provides a dump of the 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 variety of logs that are related to wireless, although much of it is only point-in-time information similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, you can run it interactively with the command sudo /usr/bin/sysdiagnose, which will give 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 Finder with Cmd+Shift+G. However, be mindful of file sizes, which are approximately 300MB.
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