How Do You Understand MacOS Issues

Understanding Internet Addressing When connecting to the Internet, you are assigned a Public IPv4 address such as 7.255.134.107 or an IPv6 address like 2000:93ae:d469:f442:cce2:1d2c:dffa:aa03. This can be verified at https://test-ipv6.com/. However, conveying these addresses to individuals who may not be technologically savvy, or even referring to MAC addresses like c7:be:e8:40:61:85, can be prone to errors and can become complex quickly. Understanding Internet Addressing When connecting to the Internet, you are assigned a Public IPv4 address such as 7.255.134.107 or an IPv6 address like 2000:93ae:d469:f442:cce2:1d2c:dffa:aa03. This can be verified at https://test-ipv6.com/. However, conveying these addresses to individuals who may not be technologically savvy, or even referring to MAC addresses like c7:be:e8:40:61:85, can be prone to errors and can become complex quickly.

Understanding Internet Addressing

When connecting to the Internet, you are assigned a Public IPv4 address such as 7.255.134.107 or an IPv6 address like 2000:93ae:d469:f442:cce2:1d2c:dffa:aa03. This can be verified at https://test-ipv6.com/. However, conveying these addresses to individuals who may not be technologically savvy, or even referring to MAC addresses like c7:be:e8:40:61:85, can be prone to errors and can become complex quickly. Additionally, this method lacks historical data, especially when previous issues arose.

When attempting to reach a webpage such as https://doyle.name, the first step is to access a DNS server to convert the host portion (doyle) combined with the Top Level Domain (name) of the URL to an IP address, such as 140.208.90.129. Each web request sent by your computer and browser includes its type, for example
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko

Significance of Default Gateways

A default gateway is typically an automatically configured address through DHCP. This gateway, such as 192.0.0.11 (usually ending in .1 or .254 based on scope size), is where your computer directs all of its traffic to be routed onwards. For IPv6, a detailed guide is available at how-to-fix-ipv6-connectivity/, and can be checked on Mac or Linux using:

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  192.0.0.11    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:fb41:1e59:c0f:9f6d%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): {126.5.199.173, 5.80.236.82}
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 c7:be:e8:40:61:85
  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 28:93:2f:0b:de:15
}

Fixing Connection Issues in Wired or Wireless Networks

When it comes to transferring 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 running 10.11.4, 11.5.1, or 12.2.1, there are various troubleshooting tools available for macOS users. 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).

Helpful Built-in Scripts

One useful 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 wide range of logs, although much of it is only relevant to wireless settings, similar to wdutil.

Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, you can use
sudo /usr/bin/sysdiagnose, although 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 or use Finder with Cmd+Shift+G to point Finder to the path. Keep in mind that the file sizes are approximately 300MB.

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