How Do You Support OSX Issues

Understanding the Functioning of Internet Addresses

When using the Internet, you are assigned a Public IPv4 address, such as 0.32.2.126, or an IPv6 address, like 2000:bab6:1ad3:6a87:ce00:44de:3756:3828. The validity of these addresses can be verified at https://test-ipv6.com/. However, attempting to communicate these addresses, or even mentioning MAC addresses like 3d:51:6b:9b:c4:58, can be prone to errors and can become complex rapidly. Moreover, this does not provide any historical data, particularly during previous instances of issues.

Navigating the Internet

When trying to access a website, such as https://beer.info, you first connect to a DNS server in order to translate the host portion (beer) combined with the Top Level Domain (info) of the URL into an IP address, like 251.196.1.73. Each web request from your computer and browser includes its type, for example,
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A.

Significance of Default Gateways

The default gateway is typically an automatically configured address via DHCP. You are provided with a default gateway, such as 172.25.115.98 (usually ending in .1 or .254 depending on the scope), where your computer forwards all its traffic to be routed further. For IPv6, we have an in-depth examination in our blog post how-to-fix-ipv6-connectivity/, but you can verify it 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  172.25.115.98    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   ce18:3264:1:2f1:a264:819a:5bf3:debd%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): {90.247.139.9, 135.47.135.194}
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 3d:51:6b:9b:c4:58
  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 f2:6f:ff:ab:b7:05
}

Resolve Issues with Wired and Wireless Connectivity

When attempting to transmit data to your router, you may use either a wired or wireless (Wi-Fi) medium at the physical and data layer.

Troubleshooting Options for Apple macOS / OSX

Regardless of your version of OSX/macOS, whether it’s 10.12.3, 11.4.2, or 12.2.5, there are various tools available for resolving issues. However, manual actions and scripts alone do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for teams that embrace remote work and Work From Anywhere (WFA).

Useful Built-in Scripts

One useful tool on OSX/macOS is the sudo wdutil info, which provides a dump of the current wireless 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 many of them are only relevant to the wireless network at a specific point in time, similar to wdutil.

sudo nohup /usr/bin/sysdiagnose -u & will run the tool in the background and write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can use
sudo /usr/bin/sysdiagnose, which will display a privacy warning. When not run in the background, the tool should open Finder in the correct location, or you can navigate to /var/tmp, or use Finder with Cmd+Shift+G to navigate to the path. Keep in mind that the file sizes are approximately 300MB or more.

Possibly Helpful Videos

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Table 1.0 - Video Help