Fix Wifi Router Issues

Understanding Internet Protocol Addressing

When connecting to the Internet, you are assigned a Public IPv4 address such as 12.94.24.59 or an IPv6 address like 2000:ccb7:d851:efc0:e447:f67d:e639:bb8f. These addresses can be verified by visiting https://test-ipv6.com/. However, conveying these addresses to those who are not technically inclined, or mentioning MAC addresses like 91:55:49:31:87:c3, can be prone to errors and become complex. Furthermore, this method does not offer any historical data, especially related to past issues.

Navigating the Internet

When accessing a website such as https://johns-mcdermott.co, the process begins with contacting a DNS server to convert the host portion (johns-mcdermott) combined with the Top Level Domain (co) of the URL into an IP address, like 187.58.196.147. Interestingly, your computer and browser transmit their type with all web requests. For instance:

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A

Significance of Default Routing

Typically, your default gateway is an address that is automatically configured via DHCP. This default gateway, such as 10.143.188.37 (usually ending in .1 or .254 based on the scope size), is where your computer sends all its traffic to be routed further. For IPv6, detailed instructions are available at how-to-fix-ipv6-connectivity/. Additionally, you can verify this on Mac or Linux by using the following command:

ifconfig | grep inet6

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  10.143.188.37    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:d5f8:94a7:4ee7:eb8b%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): {155.60.117.36, 229.115.171.171}
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 91:55:49:31:87:c3
  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 f7:67:29:59:bf:e3
}

Troubleshooting Connectivity Issues

When it comes to the physical and data layer, you might be utilizing either a wired or wireless (Wi-Fi) medium to transmit data to your router.

Resolving Problems on Apple Devices

No matter which version of OSX/macOS you are running, whether it’s “10.15.5”, “11.6.9”, or “12.0.5”, there are various tools available for resolving connectivity issues. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that are embracing remote work and Work From Anywhere (WFA).

Utilizing Pre-installed Scripts for Assistance

One extremely useful tool on OSX/macOS is “sudo wdutil info”, which provides a dump of current wireless-related settings to the CLI and can be configured to generate specific logs for troubleshooting purposes. Furthermore, the “sysdiagnose” tool can be used to generate a wide range of logs, although much of the information is only relevant to wireless settings, similar to wdutil.

To run it in the background and generate logs at “/var/tmp/.tar.gz”, use the command “sudo nohup /usr/bin/sysdiagnose -u &”. If you prefer to run it interactively, use the command “sudo /usr/bin/sysdiagnose”, which will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to “/var/tmp” manually. Keep in mind that the file sizes are approximately 300MB.

Possibly Helpful Videos

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	Securing the World's Most Dangerous Wi-Fi Network Colin Vallance WLPC Phoenix 2020	Wireless LAN Professionals
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	TIP OpenWifi Demo Network Setup for WLPC Drew Lentz WLPC Prague 2022	Wireless LAN Professionals
	Real World Protocol Analysis Peter Mackenzie WLPC_EU Lisbon 2017	Wireless LAN Professionals
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