Fix IP
Internet Addressing
On the Internet you may get a Public IPv4 address like 210.220.118.239 or an IPv6 address like 2000:d5f8:fda2:83b5:ffb6:1977:af97:f2bd. You can check this from https://test-ipv6.com/. Yet, for ‘non-techies’ to try and communicate these addresses, or even call out MAC addresses like b6:0d:b2:ef:c0:60, it can be error prone and gets complicated quickly. Additionally, this doesn’t give you any historical data (especially back when previous problems occured).
Accessing the Web
To get to a web page like https://jones-stehr.info you initially access a DNS server to translate the host portion (jones-stehr) combined with the Top Level Domain (info) of the URL, to an IP address like 146.74.63.80. Your computer and browser actually sends its type with all web requests e.g. Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Default Gateways
Your default gateway is normally an automatically configured address via DHCP. You get a default gateway like 192.168.236.182 (though they normally end in .1 or .254 depending upon the scope size) and this is where your computer sends all its traffic to be routed onwards. For IPv6 we have a deep dive on how-to-fix-ipv6-connectivity/ but you can check on Mac or Linux with:
IPv4 (inc. VPN)
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 192.168.236.182 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.
IPv6 (inc. VPN)
netstat -rn -f inet6 | egrep -i "default|2000::/3"
If you have IPv6 actvive the above should return at least one route (as per below) via a known interface such as “en0 " on a Mac.
default fe80:1ba4:1cf:e1d8:a7d5%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.
DHCP for IPv4 and IPv6
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
...
domain_name_server (ip_mult): {145.52.210.210, 10.33.113.165}
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 b6:0d:b2:ef:c0:60
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 a7:07:53:a1:7e:4e
}
Wired or Wireless
At the physical and data layer you may be using a wired or wireless (Wi-Fi) medium to send this data towards your router.
Apple macOS / OSX
No matter what version of OSX/macOS you are on, 10.12.4, 11.4.6, or 12.2.9, there are a range of tools for troubleshooting. Unfortunately, between these manual actions and scripts, they don’t give you a series of correlated values over time. This is where automated remote troubleshooting comes in to its own, especially for teams that embrace remote work and Work From Anywhere (WFA).
Scripts
One very helpful tool on OSX/macOS is sudo wdutil info which gives a dump to the CLI of current wireless related settings, and this can be configured to also generate specific logs for troubleshooting. Additionally, and perhaps more comprehensively the sysdiagnose tool can be used to generate a whole host of logs (though much is point in time only in relation to wireless just like wdutil).
sudo nohup /usr/bin/sysdiagnose -u & will run it in the background and it will write logs to /var/tmp/<blah>.tar.gz for you. If you want to run it interactively (though there is not much interaction) you can runsudo /usr/bin/sysdiagnose and it will give a privacy warning. When not run in the background it should open Finder in the correct location or you can then navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Just beware the file sizes of about 300MB more or less.
Possible Helpful Videos
P.S. PanSift Tip
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