When using the Internet, you are assigned a Public IPv4 address, such as 220.163.63.54
or an IPv6 address, such as 2000:82a6:beef:31ee:30af:1f90:c5c8:3b2
. This can be verified at https://test-ipv6.com/. However, explaining or communicating these addresses to those who are not technologically inclined, or even mentioning MAC addresses like d6:40:d2:77:df:fc
, can become difficult and prone to errors. Moreover, such an approach does not provide historical data, especially when addressing past issues.
To access a website like https://kris-carroll.com, you begin by connecting to a DNS server, which translates the host portion (kris-carroll) combined with the Top Level Domain (com) of the URL, into an IP address, such as 254.222.225.63
. Your computer and browser transmit their type with all web requests. For example:
Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
By default, your gateway is an automatically configured address through DHCP. You receive a default gateway, such as 10.175.37.16
, although they typically end in .1 or .254 based on the scope size. This is where your computer directs all its traffic to be routed further. For IPv6, detailed information is available at how-to-fix-ipv6-connectivity/. On Mac or Linux, you can verify this using the following command:
<br>
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 10.175.37.16 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 fe80:6697:5232:a030:c227%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): {0.207.209.176, 167.46.252.145} 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 d6:40:d2:77:df:fc 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 f9:0b:2a:e7:7e:c5 }
When it comes to sending data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Irrespective of whether you are using OSX or macOS, be it version 10.13.4
, 11.5.8
, or 12.0.4
, there are various tools available for troubleshooting. However, the manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes essential, especially for teams that promote remote work and Work From Anywhere (WFA).
A useful tool on OSX/macOS is the sudo wdutil info
, which provides a dump to the CLI of current wireless related settings 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 much of it is point-in-time information related to wireless, similar to wdutil.
To run sysdiagnose
in the background and write logs to /var/tmp/<blah>.tar.gz
, use the command sudo nohup /usr/bin/sysdiagnose -u &
. For an interactive run, use sudo /usr/bin/sysdiagnose
and be mindful of the file sizes, which are around 300MB.
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