How Do You Support Mac Issues
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a Public IPv4 address such as 18.41.37.100 or an IPv6 address like 2000:eb6b:c483:d605:464e:3e7a:caa0:8a6. You can verify this information by visiting https://test-ipv6.com/. However, communicating these addresses, as well as MAC addresses like 95:f6:5c:e6:b0:0e, to individuals who are not technologically inclined can be prone to error and quickly become complex. Moreover, this method does not provide any historical data, especially in cases of prior issues.
Accessing Websites
In order to visit a website, for example, https://pagac-raynor.net, your computer first contacts a DNS server to convert the host portion (pagac-raynor) along with the Top Level Domain (net) of the URL into an IP address like 181.47.184.228. Your computer and browser always include its type in all web requests, for example: Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko
Understanding the Significance of Default Gateways
Your default gateway is usually assigned an address automatically through DHCP, resulting in a default gateway like 192.0.0.88 (although they typically end in .1 or .254 depending on the scope size). This is where your computer forwards all its traffic for routing. For IPv6, a detailed explanation is available at how-to-fix-ipv6-connectivity/, but it can be checked on Mac or Linux with:
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 192.0.0.88 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 fe80:238b:be90:3082:8b05%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): {217.157.183.237, 153.49.7.4}
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 95:f6:5c:e6:b0:0e
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 be:a0:36:67:54:8b
}
Solutions for Dealing with Wired or Wireless Issues
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.
Actions to Take on Apple macOS / OSX Systems
No matter which version of macOS or OSX you are currently using, such as 10.13.3, 11.5.8, or 12.0.8, there are a variety of 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 valuable, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very helpful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. In addition, 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.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For interactive operation (although there is not much interaction), you can run sudo /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 navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind the file sizes, which are approximately 300MB more or less.
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P.S. Tips For Remote Network and Client Support
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