How Can I Test Wifi Router Issues
Understanding Internet Addressing Mechanisms
When using the Internet, individuals may be assigned a Public IPv4 address, such as 210.241.2.70, or an IPv6 address, like 2000:4899:bd91:3b91:2b09:9897:a229:b305. Verification of these addresses can be done at https://test-ipv6.com/, but conveying such addresses, along with MAC addresses like 79:93:3c:24:5c:ca, can be error-prone for those not well-versed in technology. Furthermore, obtaining historical data, particularly regarding past issues, remains a challenge.
Navigating Web Resources
Accessing a web page, such as https://kuphal-sanford.biz, commences with a query to a DNS server to translate the URL’s host segment (kuphal-sanford) combined with its Top Level Domain (biz) into the corresponding IP address, such as 7.37.153.243. Interestingly, every web request carries information about the computer and browser type, evident from the format, e.g., Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
The default gateway, typically an automatically assigned address through DHCP, serves as the focal point through which all of a computer’s traffic is forwarded. Commonly ending in .1 or .254, depending on the scope size, this gateway is represented by an address like 192.168.202.198. While a detailed guide on addressing IPv6 connectivity issues exists at how-to-fix-ipv6-connectivity/, Mac and Linux users can verify their default gateway through a few simple commands.
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 192.168.202.198 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 fe80:8a6f:b719:e7c5:5d54%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): {51.34.52.240, 23.174.86.204}
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 79:93:3c:24:5c:ca
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:b7:3a:d7:84:8d
}
Resolve Issues with Wired and Wireless Connections
When it comes to transmitting data at the physical and data layer, you might find yourself using either a wired or wireless (Wi-Fi) medium to connect to your router.
Troubleshooting Tips for Apple macOS / OSX Users
No matter which version of OSX/macOS you’re running - whether it’s 10.13.9, 11.6.3, or 12.3.9 - there are various tools available for troubleshooting. However, these manual actions and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that are actively embracing remote work and the Work From Anywhere (WFA) model.
Useful Built-in Scripts
One extremely useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the command line interface and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide array of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
By running sudo nohup /usr/bin/sysdiagnose -u &, you can run the tool in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose, but be prepared for a privacy warning. When not run in the background, it should open Finder in the correct location, allow you to navigate to /var/tmp, or use Finder with Cmd+Shift+G to locate the files. Just keep in mind that the file sizes can be around 300MB or more.
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