When using the Internet, individuals may have a Public IPv4 address such as 98.21.135.175
or an IPv6 address like 2000:e300:14b5:c3af:96ac:fd4b:5e0f:3c68
. Verification can be done at https://test-ipv6.com/. Communicating these addresses to those who are not technologically inclined or referencing MAC addresses like 1b:bf:c8:03:17:0f
can lead to errors and complications. Also, it does not provide historical data, especially about past issues.
To access a web page such as https://gibson-muller.net, the process involves accessing a DNS server to convert the host portion (gibson-muller) and the Top Level Domain (net) of the URL into an IP address, such as 106.100.180.175
. The type of computer and browser is transmitted with all web requests, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Usually, the default gateway is an address configured automatically via DHCP. A default gateway like 192.168.116.233
is received (usually ending in .1 or .254 based on scope size), and this is where all the computer’s traffic is directed for routing. For IPv6
, a comprehensive guide can be found on how-to-fix-ipv6-connectivity/, and the connectivity can be verified on Mac or Linux using:
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.116.233 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 fe80:6246:db54:3cff:a42e%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): {47.245.4.8, 60.221.156.114} 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 1b:bf:c8:03:17:0f 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 e9:3d:74:a4:1a:3e }
When it comes to transmitting data, you have the option of using either a wired or wireless (Wi-Fi) medium at the physical and data layer to reach your router.
Regardless of which version of OSX/macOS you are currently running - whether it’s 10.14.1
, 11.3.3
, or 12.0.9
- there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that are embracing remote work and the concept of Work From Anywhere (WFA).
On OSX/macOS, a highly beneficial tool is sudo wdutil info
, which provides a dump of current wireless-related settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose
tool can be used to generate a wide range of logs, though much of it is only relevant to wireless connections, similar to wdutil.
To run sysdiagnose in the background and have it write logs to /var/tmp/<blah>.tar.gz
, use the command sudo nohup /usr/bin/sysdiagnose -u &
. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose
, which 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
using Finder with Cmd+Shift+G to locate the files. Be aware that the file sizes are approximately 300MB, give or take.
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