When using the Internet, you are assigned a Public IPv4 address, such as 101.154.229.13
, or an IPv6 address, such as 2000:b37b:beed:aaf5:b6e9:bf18:b92b:4c27
. You can verify this information by visiting https://test-ipv6.com/. However, translating and communicating these addresses, as well as MAC addresses like a6:6d:ba:7a:77:8f
, can be error-prone and complex, especially for those not well-versed in the technical aspects. In addition, this method does not provide any historical data, especially for past issues.
When accessing a website, such as https://schumm.name, your computer first contacts a DNS server to convert the host name (schumm) and the Top Level Domain (name) of the URL into an IP address, such as 106.80.32.191
. Your computer and browser also transmit their information with all web requests, such as Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
.
The default gateway is typically an automatically assigned address through DHCP. It usually takes the form of an address like 192.168.147.92
(though it generally ends in .1 or .254 depending on the scope size). This is where your computer forwards all its traffic to be routed further. For IPv6
, you can find more detailed instructions on how-to-fix-ipv6-connectivity/, or you can check on Mac or Linux with:
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.147.92 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 fe80:83ee:3d22:11df:c2fa%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): {92.182.185.195, 210.117.130.80} 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 a6:6d:ba:7a:77:8f 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 64:08:f4:73:a5:71 }
In order to transmit data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Regardless of whether you are using version 10.13.9
, 11.5.2
, or 12.0.4
of OSX/macOS, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes crucial, especially for teams that have adopted remote work and the Work From Anywhere (WFA) approach.
A highly useful tool for OSX/macOS users is sudo wdutil info
, which provides a dump of current wireless settings to the CLI, and can also generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose
tool can be used to generate a wide range of logs, although much of it is limited to point-in-time information related 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 an interactive (though limited interaction) experience, you can run 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 Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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