How Can I Troubleshoot Common Wifi Connectivity
Understanding How Internet Addresses are Assigned
When connecting to the Internet, individuals are assigned a unique Public IPv4 address, such as 211.26.19.191, or an IPv6 address, like 2000:a6ae:a723:9c6a:77c:7456:a66d:1cca. These addresses can be verified using a website like https://test-ipv6.com/. However, expressing and communicating these addresses, as well as MAC addresses like c8:50:6d:92:56:07, can be challenging for those without a technical background, and may quickly become complicated. Moreover, this method does not provide historical information, particularly for past issues.
How Web Pages are Accessed
To visit a specific web page, such as https://koss-feest.info, the initial step involves accessing a DNS server to convert the host part (koss-feest) in combination with the URL’s Top Level Domain (info) into an IP address, such as 143.26.126.4. Furthermore, when making web requests, the computer and browser both transmit their type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. It is used to direct all the computer’s traffic to its intended destination, and is often in the format of 192.168.171.132 (usually ending in .1 or .254, depending on the size of the network). For IPv6, in-depth guidance is available in our article on how-to-fix-ipv6-connectivity/, along with specific instructions for Mac and Linux users.
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 192.168.171.132 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 fe80:5202:bf31:dccb:70d5%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): {43.220.151.123, 190.9.151.31}
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 c8:50:6d:92:56:07
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 85:8a:42:38:82:2c
}
Resolving Issues with Wired and Wireless Connections
When transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Guide for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using - whether it’s 10.12.3, 11.2.1, or 12.1.2 - there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting comes into play, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI, and it can also be configured to generate specific logs for troubleshooting purposes. In addition, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings at a specific time, similar to wdutil.
sudo nohup /usr/bin/sysdiagnose -u & will run the tool in the background and write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there is minimal interaction), you can executesudo /usr/bin/sysdiagnose, which will result in a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. Keep in mind that the file sizes are approximately 300MB.
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