How To Fix Common Wifi Issues
Understanding the Basics of Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 124.21.240.165, or an IPv6 address, for example, 2000:d8e:510d:f330:c96c:c151:89c7:aa2b. It is possible to verify these addresses by visiting https://test-ipv6.com/. However, it can be challenging for individuals who are not technologically inclined to convey or identify these addresses, and even MAC addresses such as e6:60:70:13:96:42. Besides, there is no provision for historical data, especially when issues occurred previously.
Navigating the Internet
Accessing a webpage like https://herman.info requires the initial interaction with a DNS server to convert the host portion (herman) combined with the Top Level Domain (info) of the URL to an IP address like 139.178.205.248. Furthermore, when making web requests, your computer and browser disclose their type, for instance: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
Ordinarily, your default gateway is an address that is configured automatically through DHCP. Typically, you will receive a default gateway such as 10.33.209.238 (although they generally end in .1 or .254 depending on the scope size), and this is where your computer directs all its traffic to be routed onwards. For IPv6, our comprehensive guide on how-to-fix-ipv6-connectivity/ provides detailed information, although you can also verify this on Mac or Linux with:
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 10.33.209.238 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 fe80:8468:c994:6e10:c57e%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): {207.222.250.224, 189.218.185.16}
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 e6:60:70:13:96:42
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 83:ef:c7:43:ca:47
}
Solutions for Wired or Wireless Connectivity Issues
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Strategies for Resolving Problems on Apple macOS / OSX
Irrespective of whether you are using OSX or macOS version 10.12.8, 11.2.2, or 12.0.5, there is a variety of troubleshooting tools available. However, they do not provide a set of correlated values over time. For this reason, automated remote troubleshooting becomes valuable, particularly for teams that adopt remote work and Work From Anywhere (WFA) practices.
Handy Scripts That Offer Assistance
A highly useful tool on OSX/macOS is the sudo wdutil info command, which provides a CLI dump of current wireless settings and can be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although most of them are specific to a particular point in time in relation to wireless, similar to wdutil.
If you want to run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, for an interactive (though limited interaction) experience, you can run sudo /usr/bin/sysdiagnose and it will prompt a privacy warning. When 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 or less.
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