How To Troubleshoot Apple Internet

Understanding Internet Addressing When using the Internet, you are assigned either a Public IPv4 address, such as 126.100.237.49, or an IPv6 address, like 2000:e645:4d36:b3c3:35f6:243:859:610e. You can verify your address at https://test-ipv6.com/. However, communicating these addresses to those unfamiliar with technology, or even sharing MAC addresses like b2:02:e0:53:1d:83, can be prone to errors and quickly become complex. Understanding Internet Addressing When using the Internet, you are assigned either a Public IPv4 address, such as 126.100.237.49, or an IPv6 address, like 2000:e645:4d36:b3c3:35f6:243:859:610e. You can verify your address at https://test-ipv6.com/. However, communicating these addresses to those unfamiliar with technology, or even sharing MAC addresses like b2:02:e0:53:1d:83, can be prone to errors and quickly become complex.

Understanding Internet Addressing

When using the Internet, you are assigned either a Public IPv4 address, such as 126.100.237.49, or an IPv6 address, like 2000:e645:4d36:b3c3:35f6:243:859:610e. You can verify your address at https://test-ipv6.com/. However, communicating these addresses to those unfamiliar with technology, or even sharing MAC addresses like b2:02:e0:53:1d:83, can be prone to errors and quickly become complex. Moreover, this information does not provide any historical data, especially when trying to diagnose past issues.

In order to access a website such as https://gottlieb.com, you first reach out to a DNS server to convert the host portion (gottlieb) combined with the Top Level Domain (com) of the URL into an IP address, such as 212.155.204.35. Your computer and browser include their type in all web requests, as shown here:
Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko

The Significance of Default Gateways

Your default gateway is typically an address that is automatically provided through DHCP. This is where your computer sends all its traffic to be routed onwards. For IPv6, you can check on Mac or Linux using the deep dive available at how-to-fix-ipv6-connectivity/. The default gateway address usually ends with .1 or .254, depending on the scope size.

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  10.5.189.236    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:f239:b909:c851:94eb%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): {147.24.229.59, 127.61.75.213}
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 b2:02:e0:53:1d:83
  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 c1:c0:b8:38:6a:66
}

Fixing 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.

Tips for Troubleshooting on Apple macOS / OSX

Regardless of the version of OSX/macOS you are running, be it 10.15.2, 11.2.8, or 12.0.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time, which is where automated remote troubleshooting becomes essential, especially for remote work and Work From Anywhere (WFA) teams.

Utilize the Native Scripts for Assistance

One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Moreover, the sysdiagnose tool can be used to generate a comprehensive range of logs, although many are only related to wireless settings. To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. Alternatively, if you prefer to run it interactively, use the command sudo /usr/bin/sysdiagnose, but be mindful of the large file sizes of about 300MB.

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