Test Common Wifi No Access
A Guide to Internet Addressing
When using the Internet, you are assigned an address that allows you to access it. This could be a Public IPv4 address, such as 21.168.87.29, or an IPv6 address, such as 2000:ca87:1ad0:3f80:d048:4c7e:1677:414e. You can verify this using a tool like https://test-ipv6.com/. However, explaining and communicating these addresses, as well as MAC addresses like d1:8c:e9:d9:3d:dd, can be complicated and prone to errors, especially for those who are not tech-savvy. Additionally, this method does not provide any historical data, particularly from previous issues.
A Look into Web Access
To reach a web page, like https://abshire.name, you first need to access a DNS server. This server translates the host portion (abshire) and the Top Level Domain (name) of the URL into an IP address, such as 10.24.170.217. When making web requests, your computer and browser also send their type, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically assigned address via DHCP. This address, like 172.19.57.22, (commonly ending in .1 or .254 depending on the scope size) is where your computer sends all its traffic to be routed onwards. For IPv6, a detailed guide on how-to-fix-ipv6-connectivity/ is available. On Mac or Linux, you can check this 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 172.19.57.22 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 fe80:1bca:aa04:e984:8e6a%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): {161.21.246.159, 18.215.63.225}
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 d1:8c:e9:d9:3d:dd
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 a7:54:4f:4b:65:24
}
Fixing Wired and Wireless Connection Issues
When it comes to sending data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Steps for Apple macOS / OSX
No matter which version of OSX/macOS you are currently using—whether it’s 10.14.9, 11.5.8, or 12.0.9—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, particularly for teams that are embracing remote work and Work From Anywhere (WFA).
Helpful Built-in Scripts
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a comprehensive range of logs, although much of it is point-in-time only in relation to wireless, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz, or to run it interactively, use sudo /usr/bin/sysdiagnose. 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.
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