Understand Common Wifi Router Issues
Understanding Internet Addressing
When using the internet, you are assigned a Public IPv4 address such as 84.160.10.192 or an IPv6 address like 2000:142f:6ea0:5fb:1fe7:3563:b3fe:f0b7. The website https://test-ipv6.com/ can help you check these addresses. However, communicating these addresses, or even mentioning MAC addresses like 07:0d:7c:e4:8a:4e, can be challenging, especially for those unfamiliar with technology. Moreover, this method does not provide any historical data, particularly from past issues.
Navigating Web Pages
In order to access a website such as https://larkin.biz, you initially connect to a DNS server to convert the host portion (larkin) along with the Top Level Domain (biz) of the URL, to an IP address like 206.49.140.125. Your computer and browser transmit its type with each web request, for example: 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
By default, your gateway is automatically assigned through DHCP, typically ending with .1 or .254 depending on the scope size, such as 10.251.104.234. This is where your computer forwards all its traffic to be routed onwards. For IPv6, detailed information on how-to-fix-ipv6-connectivity/ can be found, and checking on Mac or Linux can be done with:
ip -6 route
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 10.251.104.234 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 fe80:82d1:30e9:3713:fa91%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): {160.184.88.238, 62.33.129.14}
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 07:0d:7c:e4:8a:4e
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 e1:4a:ed:c6:d8:8e
}
Resolving Connectivity Issues with Wired or Wireless Networks
When it comes to transmitting data to your router at the physical and data layer, you might be using either a wired or wireless (Wi-Fi) medium.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you are currently running - whether it’s 10.11.1, 11.4.7, or 12.0.9 - there are various tools available for troubleshooting. However, these manual actions and scripts fail to provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly valuable, especially for teams that are embracing remote work and the Work From Anywhere (WFA) concept.
In-Built Tools for Assistance
One extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the command line interface (CLI). This tool can also be configured to generate specific logs for troubleshooting purposes. Another comprehensive option is the sysdiagnose tool, which can generate a wide range of logs, although much of it is related to wireless settings and is only a snapshot in time, similar to the wdutil tool.
To run the sysdiagnose tool in the background and have it write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose (although there is minimal interaction). Running it without the background option should open Finder in the correct location, or you can navigate to the path /var/tmp using Finder with Cmd+Shift+G. However, be mindful of the file sizes, which are typically around 300MB.
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