When using the Internet, individuals may be assigned a Public IPv4 address, such as 69.213.88.130
, or an IPv6 address like 2000:e7a3:469c:825d:c12:4fff:6800:2097
. This assignment can be verified at https://test-ipv6.com/. However, expressing and relaying these addresses, as well as MAC addresses like 35:0f:d5:de:51:87
, can be prone to error and complicated, particularly for those not well-versed in technology. Additionally, it does not provide any historical data, especially in instances where previous issues arose.
To access a webpage, such as https://gutmann-schiller.name, one must first contact a DNS server in order to convert the host portion (gutmann-schiller) combined with the Top Level Domain (name) of the URL to an IP address, like 247.98.45.170
. Each time a computer and browser make web requests, they send specific type information, such as Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
.
Typically, the default gateway is an automatically assigned address via DHCP. An individual’s default gateway, such as 172.18.155.56
(typically ending in .1 or .254 based on the scope size), is where their computer sends all traffic to be routed onwards. For IPv6
, a comprehensive guide can be found at how-to-fix-ipv6-connectivity/, and can also be verified on Mac or Linux using the following command.
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 172.18.155.56 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 fe80:426b:13c1:9539:bb28%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): {26.177.164.106, 163.93.88.180} 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 35:0f:d5:de:51:87 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 5e:f8:05:eb:81:64 }
When it comes to transmitting data to your router, you might be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
No matter which version of OSX/macOS you’re using, whether it’s 10.14.1
, 11.1.2
, or 12.0.2
, there are various tools available for troubleshooting. However, these manual actions and scripts don’t provide a series of correlated values over time, making automated remote troubleshooting essential, particularly for teams that embrace remote work and Work From Anywhere (WFA).
One useful tool on OSX/macOS is sudo wdutil info
, which provides a dump of current wireless 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 many are only relevant at a specific time 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
. If you prefer to run it interactively, you can usesudo /usr/bin/sysdiagnose
which will prompt a privacy warning. If not running 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 about 300MB more or less.
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