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Demystifying Internet Addressing
When using the Internet, you are assigned either a Public IPv4 address (e.g. 219.64.249.60) or an IPv6 address (e.g. 2000:301d:3f83:519a:b4be:81bd:6370:4e5). These unique identifiers can be verified at https://test-ipv6.com/. However, conveying these addresses, and even referencing MAC addresses such as 63:40:be:29:18:3a, can be prone to errors and become complex, especially for individuals who are not technology-savvy. Furthermore, it does not provide historical data, which is particularly important when troubleshooting past issues.
Understanding Web Page Access
Accessing a web page, such as https://rodriguez.net, initially involves querying a DNS server to translate the URL’s host portion (rodriguez) and its Top Level Domain (net) into an IP address, such as 235.36.224.198. Your computer and browser include their type in all web requests, for example:
Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
Unveiling the Significance of Default Gateways
The default gateway is typically an automatically assigned address through DHCP. It serves as the endpoint to which your computer sends all its traffic to be routed onwards. For IPv6, detailed information on this topic can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this by:
```bash
ifconfig
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 192.168.80.188 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 fe80:45f1:a216:56a0:f275%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): {85.253.11.28, 23.54.82.219}
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 63:40:be:29:18:3a
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 55:df:85:b8:5f:d2
}
Fixing Connectivity Issues for Wired and Wireless Networks
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 Solutions for Apple macOS / OSX
No matter which version of macOS or OSX you are working on, whether it’s 10.11.8, 11.2.3, or 12.1.3, 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 teams that support remote work and Work From Anywhere (WFA).
Useful Scripts That Come Pre-Installed
A useful tool on OSX/macOS is the 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. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is point-in-time only in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can run sudo /usr/bin/sysdiagnose (although there is not much interaction) and it will give 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 Cmd+Shift+G to locate the path. Keep in mind that the file sizes are approximately 300MB.
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P.S. Tips For Remote Network and Client Support
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