Test MacOS IP Settings
Understanding Internet Addressing
When connecting to the internet, you will receive an IPv4 or IPv6 address. These addresses can be complex and difficult for non-technical individuals to communicate or understand. Additionally, they do not provide historical data.
Navigating the World Wide Web
Accessing a website involves translating the URL to an IP address with the help of a DNS server. Your computer and browser also send specific information with each web request.
The Significance of Default Gateways
The default gateway, typically obtained through DHCP, is where your computer sends all its traffic to be routed onwards. There are also troubleshooting methods for IPv6 connectivity on Mac or Linux.
IPv4 Routes and the Host IPv4 Route Table (inc. VPN)
netstat -rn -f inet | egrep -i "default|0/1|128.0/1"
0/1 172.18.12.193 UGScg utun3 default 172.21.251.30 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 Routes and the Host IPv6 Route Table (inc. VPN)
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:c663:e050:1409:f6dc%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.
Debugging DHCP for both IPv4 and IPv6
To get a look at the low level DHCP configuration (Mac/Linux):
ipconfig getpacket en0
...
domain_name_server (ip_mult): {165.217.230.110, 184.53.161.103}
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 f6:6f:ab:60:01:62
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 27:e6:1f:5c:32:e3
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of whether you are running OSX/macOS version 10.14.1, 11.5.8, or 12.2.2, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have adopted remote work and the Work From Anywhere (WFA) concept.
Pre-installed Scripts for Assistance
A useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of current wireless settings and can also be configured to generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be utilized to produce a wide range of logs, although much of it is only relevant to wireless at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs at /var/tmp/<blah>.tar.gz. For an interactive run (even though there is minimal interaction), you can use sudo /usr/bin/sysdiagnose, which will trigger a privacy warning. If 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. Keep in mind that the file sizes are approximately 300MB.
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