How To Check Wifi Router Issues
Understanding the Function of Internet Addressing
When using the Internet, you will be assigned a unique IPv4 address, such as 238.70.32.189, or an IPv6 address, like 2000:d07c:95fa:451e:9537:4684:11a0:5e. You can verify this information at https://test-ipv6.com/. However, conveying these addresses to individuals who are not tech-savvy, or even mentioning MAC addresses like 14:b6:83:6e:d7:dc, can be error-prone and become complex. It also does not provide any historical context for previous issues.
Navigating the Internet
In order to access a website, such as https://kshlerin.info, your computer first communicates with a DNS server to convert the host portion (kshlerin) combined with the Top Level Domain (info) of the URL into an IP address, such as 209.211.206.87. Furthermore, your computer and browser include its type in all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Significance of the Default Gateways
The default gateway is typically an automatically generated address through DHCP. It assigns a default gateway, such as 192.168.93.37 (usually ending in .1 or .254 based on the scope size), where your computer directs all of its traffic to be routed. For troubleshooting IPv6 connectivity, there are in-depth resources available here, or you can perform checks 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 192.168.93.37 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 fe80:9150:99c6:88c2:8669%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): {133.6.231.61, 160.254.6.160}
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 14:b6:83:6e:d7:dc
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 88:6c:5b:92:e0:e4
}
Resolving Wired and Wireless Connection Issues
When it comes to transmitting data to your router, you may encounter issues with the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.13.7, 11.4.8, or 12.2.8, there are various 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 beneficial, particularly for teams that support remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very useful tool in OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is point-in-time information related to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. For interactive use, you can run sudo /usr/bin/sysdiagnose and it will give a privacy warning. If 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. Keep in mind that the file sizes are approximately 300MB.
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