Fix Common Wifi Issues
Understanding IP Addressing
In the world of the Internet, individuals are assigned unique IP addresses, such as 252.237.24.27 for IPv4 or 2000:e67:503e:41be:3ec5:f228:14b8:c0df for IPv6. Verifying this information can be done at https://test-ipv6.com/. However, explaining and working with these addresses, including MAC addresses like 58:17:aa:02:b9:c7, can be challenging for those without technical expertise. Moreover, this method does not provide any historical data, particularly during prior issues.
Navigating through the Internet
In order to reach a website, such as https://reilly.info, a DNS server is initially accessed to convert the host portion (reilly) combined with the Top Level Domain (info) of the URL to an IP address, such as 110.138.119.34. Furthermore, when making web requests, your computer and browser provide their type, for instance: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Significance of Default Gateways
Typically, your default gateway is automatically configured via DHCP, resulting in an address such as 172.19.145.69 (commonly ending in .1 or .254 depending on scope size). This is the location where all of your computer’s traffic is sent for further routing. To address IPv6 connectivity concerns, a comprehensive guide is available at how-to-fix-ipv6-connectivity/. Users can also perform checks on Mac or Linux using the following method:
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 172.19.145.69 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 fe80:9252:5844:c242:bf6f%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): {171.217.157.137, 180.176.84.179}
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 58:17:aa:02:b9:c7
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 54:f0:d6:8c:d8:da
}
Fixing Issues with Wired and Wireless Networks
When sending data to your router, you may encounter issues at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting on Apple’s macOS / OSX Operating System
No matter which version of OSX/macOS you are using - whether it’s 10.14.6, 11.2.1, or 12.3.2, 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 valuable, especially for teams embracing remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of 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 wide range of logs, although much of it is only related to wireless settings and is not continuous like wdutil.
To run the sysdiagnose tool in the background, you can use sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, but beware of the large file sizes of about 300MB.
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