How To Understand Wifi Internet Issues
Understanding Internet Addressing
When using the Internet, you are assigned a unique Public IPv4 address, such as 251.21.226.78, or an IPv6 address like 2000:16d1:c20c:adb6:dc0c:9bd6:a541:6d31. To verify your address, you can visit https://test-ipv6.com/. However, when trying to share these addresses with those who are not tech-savvy, or even attempting to identify MAC addresses like a4:1a:16:8c:d1:8e, it can quickly become complex and prone to errors. Furthermore, this method does not provide any historical data, particularly when encountering past issues.
Navigating the Internet
In order to access a webpage like https://grady.biz, you must first contact a DNS server to convert the host portion (grady) in combination with the Top Level Domain (biz) of the URL into an IP address, such as 88.76.105.182. Additionally, your computer and browser include specific identification with every web request, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically assigned address via DHCP, such as 10.54.174.98 (although they usually end in .1 or .254 depending on the scope size). This is where your computer directs all of its traffic to be routed onwards. For more in-depth information on IPv6, you can refer to how-to-fix-ipv6-connectivity/, but you can also verify this on Mac or Linux by 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 10.54.174.98 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:cd96:ae63:4834:dad6%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): {212.137.55.113, 29.216.64.226}
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 a4:1a:16:8c:d1:8e
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 ca:6e:dc:d0:ab:67
}
Resolving Issues with Wired and Wireless Connections
When it comes to the physical and data layer, you may utilize either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Troubleshooting Solutions for Apple macOS / OSX Users
Regardless of your OSX/macOS version - whether it’s 10.14.2, 11.0.7, or 12.0.3, 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 essential, especially for remote work and Work From Anywhere (WFA) teams.
Useful Built-in Scripts
A highly beneficial tool in OSX/macOS is the sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is point-in-time related to wireless, similar to wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive option, use sudo /usr/bin/sysdiagnose and navigate to the correct location in Finder or through /var/tmp. Keep in mind that the file sizes can be around 300MB.
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