When using the Internet, individuals may acquire a Public IPv4 address, such as 152.210.12.254
, or an IPv6 address like 2000:430a:ab99:6f5a:e2e:63b7:e4ac:c2ec
. This can be verified at https://test-ipv6.com/. Communicating these addresses or even citing MAC addresses like 06:27:74:2e:8b:fb
can be prone to errors and becomes complex. Furthermore, it does not provide any historical data, particularly during previous incidents.
To access a webpage, such as https://west.info, one initially contacts a DNS server to convert both the host portion (west) and the Top Level Domain (info) of the URL into an IP address, for example, 188.217.62.249
. When making web requests, the computer and browser actually include information about its type, such as Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0
The default gateway is typically an automatically assigned address through DHCP. For instance, a default gateway like 192.168.173.201
(usually ending in .1 or .254 depending on the scope size) is where all the computer’s traffic is sent to be routed further. For IPv6
, a detailed analysis is available at how-to-fix-ipv6-connectivity/, but it can also be checked on Mac or Linux using:
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.173.201 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.
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 fe80:3b8c:1e2a:eb9d:4791%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.
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
... domain_name_server (ip_mult): {225.2.50.248, 124.191.101.136} 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 06:27:74:2e:8b:fb 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 a8:16:7a:02:52:d5 }
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Regardless of the version of OSX/macOS you are using, whether it’s 10.14.4
, 11.6.9
, or 12.3.3
, there are various tools available for troubleshooting. However, manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are engaged in remote work and Work From Anywhere (WFA).
On OSX/macOS, the sudo wdutil info
tool is very helpful as it provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Another comprehensive tool is the sysdiagnose
tool, which can generate a variety of logs related to wireless issues (though most of it is point-in-time data, similar to wdutil).
Running sudo nohup /usr/bin/sysdiagnose -u &
will execute the tool in the background and write logs to /var/tmp/<blah>.tar.gz
. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose
with a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp
and view the file sizes, which are usually around 300MB.
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