How Can I Support Mac IP Settings
Functioning of Internet Addressing
When using the internet, it is common to have a Public IPv4 address such as 112.29.2.22 or an IPv6 address like 2000:8954:fc3d:73da:9c95:3dc5:e759:7264. Verification of this information can be done at https://test-ipv6.com/. However, relaying these addresses and MAC addresses such as 26:69:85:b0:b9:76 to individuals who are not technologically savvy can be prone to errors and can become complex very quickly. Furthermore, it does not provide any historical data, especially when dealing with past issues.
Navigating the World Wide Web
In order to access a webpage, such as https://prosacco.org, the first step is to contact a DNS server to convert the host portion (prosacco) combined with the Top Level Domain (org) of the URL into an IP address, such as 200.40.219.125. Each web request from your computer and browser includes its type, for example Mozilla/5.0 (Windows; U; Win 9x 4.90; SG; rv:1.9.2.4) Gecko/20101104 Netscape/9.1.0285
Significance of Default Gateways
The default gateway is typically an address that is automatically configured through DHCP. It usually comes in the form of a default gateway like 192.168.208.54, with the final number often being either .1 or .254, depending on the size of the scope. This is the destination where all traffic from your computer is sent to be routed onwards. Additional information on IPv6 can be found in a detailed analysis on how-to-fix-ipv6-connectivity/, and can be verified on Mac or Linux through the following code:
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 192.168.208.54 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 fe80:6bb5:8d12:c6c:da9b%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): {203.160.127.18, 172.104.35.42}
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 26:69:85:b0:b9:76
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 62:7f:f7:92:c4:e3
}
Resolving Connectivity Issues for Wired and Wireless Networks
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.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.15.4, 11.2.2, or 12.0.2, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, which is crucial for effective troubleshooting. This is where automated remote troubleshooting proves to be beneficial, particularly for teams that are working remotely or embracing a Work From Anywhere (WFA) setup.
Utilizing Built-in Scripts for Assistance
One valuable tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a comprehensive range of logs, although many of these logs only capture point-in-time data in relation to wireless, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, you can 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. However, be mindful of the large file sizes, usually around 300MB.
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