When using the Internet, you are assigned a unique Public IPv4 address such as 121.169.79.137
or an IPv6 address like 2000:e90e:8f79:30ee:25f9:838:7455:44e6
. You can verify these addresses by visiting https://test-ipv6.com/. However, for those not well-versed in technology, conveying these addresses or even referring to MAC addresses like 23:90:6f:e7:41:57
can quickly become complex and error-prone. Furthermore, this method does not provide any historical data regarding past issues.
In order to access a website such as https://mccullough.org, your computer first contacts a DNS server to translate the host (mccullough) along with the Top Level Domain (org) of the URL into an IP address like 187.87.55.219
. Your computer and browser also transmit their type with all web requests, for example:
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, such as 192.0.0.219
(usually ending in .1 or .254 depending on the scope size). This is the point to which your computer directs all its traffic to be routed onwards. For IPv6
, detailed instructions can be found in our blog post titled how-to-fix-ipv6-connectivity/, although you can also check on Mac or Linux by 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 192.0.0.219 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 fe80:4326:5b18:6ff3:1e2e%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): {239.117.252.164, 152.199.146.79} 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 23:90:6f:e7:41:57 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 f3:80:43:26:ca:90 }
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.
Regardless of whether you are using OSX or macOS version 10.14.6
, 11.5.9
, or 12.0.8
, there are various troubleshooting tools available. However, these tools do not provide a set of correlated values over time, which is where automated remote troubleshooting can be beneficial, especially for teams that are working remotely or embracing the Work From Anywhere (WFA) concept.
A very 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 most of the information is only related to wireless settings, similar to wdutil.
To run sysdiagnose
in the background and write the logs to /var/tmp/<blah>.tar.gz
, you can use the command sudo nohup /usr/bin/sysdiagnose -u &
. Alternatively, you can run it interactively by using the command sudo /usr/bin/sysdiagnose
and then navigating to the path /var/tmp
in Finder or using the shortcut Cmd+Shift+G. Keep in mind that the file sizes are approximately 300MB.
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