When using the Internet, individuals are assigned a Public IPv4 or IPv6 address, such as 217.104.187.217
or 2000:16af:46cc:6dbc:fd28:b357:8a33:59e6
. These addresses can be verified by visiting https://test-ipv6.com/. Communicating these addresses, such as MAC addresses like 79:f5:fa:7f:7d:ed
, can be complex and error-prone, especially for those unfamiliar with technical terminology. Additionally, they do not provide historical data, which is important for troubleshooting past issues.
When accessing a website like https://vonrueden.biz, the initial step is to contact a DNS server to convert the URL’s host portion (vonrueden) and Top Level Domain (biz) to an IP address, like 67.44.92.133
. Additionally, each web request contains information about the type of computer and browser being used, such as Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
.
The default gateway is typically an automatically assigned address through DHCP, often ending in .1 or .254 depending on the scope size. This is the location to which a computer sends all its traffic to be routed onwards. For information specific to IPv6
, a detailed guide is available at how-to-fix-ipv6-connectivity/, and instructions for checking on Mac or Linux systems are provided.
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 10.110.229.77 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 fe80:95d0:385d:a9ac:b887%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): {44.217.55.114, 255.233.236.178} 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 79:f5:fa:7f:7d:ed 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 b9:de:26:37:16:d9 }
When it comes to sending 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 OSX/macOS 10.14.3, 11.3.5, or 12.3.3, there are a variety of tools available for troubleshooting connectivity issues. However, these tools do not provide a set of correlated values over time, making automated remote troubleshooting especially valuable for teams engaging in remote work or the Work From Anywhere (WFA) model.
An extremely useful tool on OSX/macOS is the sudo wdutil info
command, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose
tool can be used to generate a comprehensive set of logs, although many of these logs are only related to wireless and are point-in-time.
To run the sysdiagnose
tool in the background and write logs to /var/tmp/<blah>.tar.gz
, use the following command: sudo nohup /usr/bin/sysdiagnose -u &
. If you prefer to run it interactively, use sudo /usr/bin/sysdiagnose
, but keep in mind that it 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, or use Cmd+Shift+G in Finder to point it to the path. Be cautious of the file sizes, which are typically around 300MB.
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