How Do You DiagnOSe Wifi Issues

Understanding IP Addresses When using the Internet, you are assigned an IP address such as 50.95.114.155 (IPv4) or 2000:2273:5f4e:3337:536e:9699:88a1:d4e5 (IPv6). These can be verified on https://test-ipv6.com/. However, conveying and managing these addresses, as well as MAC addresses like d9:6c:0b:e0:1a:df, can be error-prone and complex for non-technical users. Understanding IP Addresses When using the Internet, you are assigned an IP address such as 50.95.114.155 (IPv4) or 2000:2273:5f4e:3337:536e:9699:88a1:d4e5 (IPv6). These can be verified on https://test-ipv6.com/. However, conveying and managing these addresses, as well as MAC addresses like d9:6c:0b:e0:1a:df, can be error-prone and complex for non-technical users.

Understanding IP Addresses

When using the Internet, you are assigned an IP address such as 50.95.114.155 (IPv4) or 2000:2273:5f4e:3337:536e:9699:88a1:d4e5 (IPv6). These can be verified on https://test-ipv6.com/. However, conveying and managing these addresses, as well as MAC addresses like d9:6c:0b:e0:1a:df, can be error-prone and complex for non-technical users. This method also lacks historical data, especially relating to previous issues.

When accessing a website such as https://stark.name, the initial step involves using a DNS server to convert the URL’s host portion (stark) along with the Top Level Domain (name) to an IP address like 83.46.147.43. Additionally, your computer and browser both provide their type with each web request, for example:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A

The Significance of Default Gateways

The default gateway is typically automatically configured via DHCP and is usually an address ending in .1 or .254, depending on the scope size, such as 172.26.169.168. This is where your computer directs all traffic for routing. For IPv6, a more detailed explanation is available at how-to-fix-ipv6-connectivity/ and can be verified 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  172.26.169.168    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:dfb5:7c5a:c9f:4a26%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): {22.44.28.9, 180.222.229.177}
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 d9:6c:0b:e0:1a:df
  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 a2:7a:ab:b5:0b:83
}

Resolving Issues with Wired and Wireless Connections

When it comes to transmitting data, whether through a wired or wireless (Wi-Fi) medium, it is important to troubleshoot any issues that may arise at the physical and data layer, especially when dealing with your router.

Addressing Problems on Apple macOS / OSX Systems

No matter which version of OSX/macOS you are using, whether it’s 10.15.7, 11.3.6, or 12.2.1, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a comprehensive set of correlated values over time. This is where automated remote troubleshooting becomes valuable, particularly for teams that have embraced remote work and Work From Anywhere (WFA) arrangements.

Utilizing Pre-Installed Scripts for Assistance

One useful 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 troubleshooting logs. Additionally, the sysdiagnose tool can generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & will execute the tool in the background, writing logs to /var/tmp/<blah>.tar.gz. For an interactive run (although there is minimal interaction), you can use sudo /usr/bin/sysdiagnose, which 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 the Cmd+Shift+G command. Be mindful of the file sizes, which typically range around 300MB.

Possibly Helpful Videos

Video Title Channel
Securing the World's Most Dangerous Wi-Fi Network Colin Vallance WLPC Phoenix 2020 Wireless LAN Professionals
Wireless Adjuster Certification - Do You Need It? Wireless LAN Professionals
Real World Protocol Analysis Peter Mackenzie WLPC_EU Lisbon 2017 Wireless LAN Professionals
Next Generation Troubleshooting with Meraki Wireless Devin Barger WLPC Prague 2018 Wireless LAN Professionals
The Importance of Broadcast/Multicast Filtering in Wi-Fi HD Arjan Koopen WLPC EU Budapest 2016 Wireless LAN Professionals
Table 1.0 - Video Help



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