When connecting to the Internet, one may be assigned a public IPv4 address such as 95.206.181.47
or an IPv6 address like 2000:7c99:d89a:2f38:ccac:8aaa:99b6:da48
. These addresses can be verified using https://test-ipv6.com/. However, articulating and working with these addresses, including MAC addresses such as 75:6d:ea:3c:92:fd
, can be complex and prone to errors, especially for individuals who are not well-versed in technology. Moreover, this method does not provide any historical data related to past issues.
When trying to reach a website like https://rolfson.info, the first step involves accessing a DNS server to translate the URL’s host portion (rolfson) combined with its Top Level Domain (info) to an IP address such as 178.218.49.4
. The computer and browser also transmit information about their type with every web request, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Typically, the default gateway is an address that is automatically configured through DHCP. It is the point to which all of the computer’s traffic is routed, with examples of default gateways being addresses like 192.168.36.93
(commonly ending in .1 or .254 depending on the scope size). Those seeking to delve into IPv6
and troubleshoot can find in-depth information on how-to-fix-ipv6-connectivity/, and Mac or Linux users can verify this information using the command:
command-goes-here
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.36.93 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 fe80:622a:8caa:3305:b62f%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): {35.45.246.133, 174.172.245.118} 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 75:6d:ea:3c:92:fd 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 bd:42:5b:e2:75:3b }
When it comes to transmitting data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
No matter which version of OSX/macOS you are currently using, whether it’s 10.14.8
, 11.2.2
, or 12.2.4
, there are various tools available for troubleshooting. However, these tools do not provide a series of correlated values over time, unlike automated remote troubleshooting, which is particularly beneficial for remote work and Work From Anywhere (WFA) teams.
An extremely useful tool for OSX/macOS troubleshooting is sudo wdutil info
, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose
tool is even more comprehensive and can generate a wide range of logs, though many are only relevant to wireless at a specific moment, similar to wdutil.
To run it in the background and generate logs, use the command sudo nohup /usr/bin/sysdiagnose -u &
, which will write logs to /var/tmp/<blah>.tar.gz
. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose
(although there is not much interaction) and it will provide 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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