DiagnOSe Common Wifi Internet Issues
Functioning of Internet Addressing
When using the Internet, individuals may receive a Public IPv4 address such as 87.132.45.123 or an IPv6 address like 2000:a7b2:1bf5:2e5e:a2f2:afc6:ee8:22aa. The accessibility of these addresses can be confirmed at https://test-ipv6.com/. However, conveying these addresses to non-technical individuals or mentioning MAC addresses like 0c:ab:75:ea:03:3e can be prone to errors and can become complex. Furthermore, this method does not provide historical data on previous issues.
Web Navigation
When attempting to access a webpage such as https://miller.biz, the initial step involves contacting a DNS server to convert the host portion (miller) in combination with the Top Level Domain (biz) of the URL to an IP address like 209.227.152.61. With every web request, your computer and browser also send its specifications, for instance: Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Significance of Default Gateways
Typically, your default gateway is an automatically assigned address via DHCP. The default gateway, which is where your computer forwards all of its traffic, is typically an address such as 172.17.130.235 (usually ending in .1 or .254 based on the scope size). For IPv6, detailed instructions are available in the blog post how-to-fix-ipv6-connectivity/, and can be verified on Mac or Linux by using:
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 172.17.130.235 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 fe80:1caa:353f:9892:f043%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): {4.145.70.174, 224.120.125.169}
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 0c:ab:75:ea:03:3e
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 1d:be:4a:34:cf:de
}
Resolving Issues with Wired and Wireless Connections
When it comes to sending data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Tips for Addressing Problems on Apple macOS / OSX
Irrespective of the version of OSX/macOS you are using, whether it’s 10.15.9, 11.3.1, or 12.0.8, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. In such cases, automated remote troubleshooting becomes extremely valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Embedded Scripts for Assistance
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless related settings to the CLI, and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless network issues, similar to the wdutil tool.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute this tool in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. For an interactive option (although there is not much interaction), you can runsudo /usr/bin/sysdiagnose, and it will display a privacy warning. If 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 point Finder to the path. However, be mindful of the file sizes, which are approximately 300MB more or less.
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