How Can I Test Mac No-access
The Fundamentals of Internet Address System
When using the Internet, individuals may receive a Public IPv4 address such as 177.196.229.3 or an IPv6 address like 2000:bd4:9c2c:d023:f7ff:8550:7ed6:18a9. A convenient way to verify this information is through https://test-ipv6.com/. However, explaining or referencing these addresses, including MAC addresses like 3a:6b:ab:2f:c6:58, can be prone to errors and rapidly become complex, particularly for those without technical expertise. Furthermore, this method does not provide any historical data, especially for past issues.
How Web Pages are Accessed
When accessing a website such as https://rolfson.info, the first step involves connecting to a DNS server in order to convert the combination of the host part (rolfson) and the Top Level Domain (info) of the URL into an IP address, for example, 157.133.14.54. It is important to note that the computer and browser automatically transmits its type with all web requests, e.g. Mozilla/5.0 (Windows NT x.y; Win64; x64; rv:10.0) Gecko/20100101 Firefox/10.0.
Understanding the Significance of Default Gateways
The default gateway is typically an automatically assigned address provided through DHCP. An example of a default gateway would be 10.209.190.213, with the last digits typically being .1 or .254 depending on the scope size. This is where all of the computer’s traffic is directed for further routing. To delve deeper into configuring this for IPv6, comprehensive instructions can be found at how-to-fix-ipv6-connectivity/. On Mac or Linux, this can also be verified.
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 10.209.190.213 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 fe80:72ce:d45b:b842:db99%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): {188.128.130.156, 28.162.191.91}
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 3a:6b:ab:2f:c6:58
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 46:aa:69:ea:51:f0
}
Fixing Connectivity Issues
When it comes to transmitting data to your router, you may encounter connectivity issues at the physical and data layer, whether you are using a wired or wireless (Wi-Fi) medium.
Troubleshooting Tips for Apple macOS / OSX
Regardless of which version of OSX/macOS you are using, be it 10.11.6, 11.1.5, or 12.2.8, there are various tools available for troubleshooting. However, these 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 have adopted remote work and Work From Anywhere (WFA).
Useful Built-in Tools
One of the helpful tools on OSX/macOS is sudo wdutil info, 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 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/
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