When using the Internet, you are assigned either a Public IPv4 address, such as 126.100.237.49
, or an IPv6 address, like 2000:e645:4d36:b3c3:35f6:243:859:610e
. You can verify your address at https://test-ipv6.com/. However, communicating these addresses to those unfamiliar with technology, or even sharing MAC addresses like b2:02:e0:53:1d:83
, can be prone to errors and quickly become complex. Moreover, this information does not provide any historical data, especially when trying to diagnose past issues.
In order to access a website such as https://gottlieb.com, you first reach out to a DNS server to convert the host portion (gottlieb) combined with the Top Level Domain (com) of the URL into an IP address, such as 212.155.204.35
. Your computer and browser include their type in all web requests, as shown here: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Your default gateway is typically an address that is automatically provided through DHCP. This is where your computer sends all its traffic to be routed onwards. For IPv6
, you can check on Mac or Linux using the deep dive available at how-to-fix-ipv6-connectivity/. The default gateway address usually ends with .1 or .254, depending on the scope size.
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 10.5.189.236 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:f239:b909:c851:94eb%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): {147.24.229.59, 127.61.75.213} 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 b2:02:e0:53:1d:83 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 c1:c0:b8:38:6a:66 }
When it comes to transmitting data to your router, you may be using either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Regardless of the version of OSX/macOS you are running, be it 10.15.2
, 11.2.8
, or 12.0.4
, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for remote work and Work From Anywhere (WFA) teams.
One useful tool on OSX/macOS is the sudo wdutil info
command, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Moreover, the sysdiagnose
tool can be used to generate a comprehensive range of logs, although many are only related to wireless settings. To run it in the background and write logs to /var/tmp/<blah>.tar.gz
, use the command sudo nohup /usr/bin/sysdiagnose -u &
. Alternatively, if you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose
, but be mindful of the large file sizes of about 300MB.
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