How Do You DiagnOSe Wifi Connectivity
Understanding Internet Addressing Principles
When using the Internet, you are assigned a Public IPv4 address, such as 185.214.214.47, or an IPv6 address, like 2000:4c0d:1e7c:519a:d658:1e7d:dd73:b97e. You can verify this information by visiting https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or identifying MAC addresses, such as ea:46:0b:87:96:ab, can be error-prone and complex. Furthermore, this method does not provide historical data, especially when looking back at past issues.
Navigating the Internet
In order to access a web page like https://jakubowski-heaney.org, you must first contact a DNS server to convert the host portion (jakubowski-heaney) combined with the Top Level Domain (org) of the URL into an IP address, such as 241.248.39.247. Additionally, when making web requests, your computer and browser send their type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP, such as 172.21.2.38 (usually ending in .1 or .254 depending on the scope size). This is where your computer sends all of its traffic to be routed onward. For detailed information about setting up IPv6, refer to our guide on how-to-fix-ipv6-connectivity/. Additionally, you can verify this on Mac or Linux using the following command:
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 172.21.2.38 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 fe80:8ef0:1794:401d:6ec9%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): {30.125.190.230, 86.199.130.110}
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 ea:46:0b:87:96:ab
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 66:84:39:c4:85:e2
}
Fixing Connectivity Issues for Wired and Wireless Networks
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.
Troubleshooting Tips for Mac Operating Systems
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.8, 11.4.2, or 12.2.9, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes essential, particularly for teams that are embracing remote work and operating from anywhere (WFA).
Useful Built-in Scripts
One incredibly useful tool on OSX/macOS is the sudo wdutil info, 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 many of them are only relevant to wireless at a specific point in time, much like wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose. Be cautious of the file sizes, which are approximately 300MB or more.
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