How Can I DiagnOSe Apple IP Settings

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### IPv4 Routes and the Host IPv4 Route Table (inc. VPN)
```netstat -rn -f inet | egrep -i "default|0/1|128.0/1"```

<pre>
0/1      172.18.12.193  UGScg  utun3
default  10.44.77.6    UGScg  en0
128.0/1  172.18.12.193  UGSc   utun3</pre>

**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. 

<pre>
default   fe80:99d0:eb91:c11b:d3bd%en0  UGcg   en0
default   fe80::%utun0                   UGcIg  utun0
default   fe80::%utun1                   UGcIg  utun1
default   fe80::%utun2                   UGcIg  utun2
2000::/3  utun3                          USc    utun3</pre>

**Note:** We are not just looking for the default but also for any VPN that overrides the public v6 address space.
<br>

## Debugging DHCP for both IPv4 and IPv6

To get a look at the low level DHCP configuration (Mac/Linux): 

```ipconfig getpacket en0```

<pre>
...
domain_name_server (ip_mult): {173.138.218.182, 236.55.55.15}
end (none):
...</pre>

So, in the above we are not getting IPv6 DNS servers from the DHCPv4 reply but...

```ipconfig getv6packet en0```

<pre>
DHCPv6 REPLY (7) Transaction ID 0x80940b Length 76
Options[4] = {
  CLIENTID (1) Length 14: DUID LLT HW 1 Time 668691856 Addr 1e:2f:91:14:67:92
  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 ee:33:fe:b3:a3:e1
}</pre>




## Resolving Connectivity Issues: Wired vs. Wireless
When it comes to transmitting data to your router, you may be utilizing either a wired or wireless (Wi-Fi) medium at the physical and data layer.
### Troubleshooting Methods for Apple macOS / OSX
Irrespective of the version of OSX/macOS you are running, whether it's ```10.12.3```, ```11.3.4```, or ```12.1.9```, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that adopt remote work and the Work From Anywhere (WFA) concept.
#### Utility Scripts Offered by Operating System
An extremely useful tool on OSX/macOS is ```sudo wdutil info```, which provides a dump to the CLI of current wireless settings and can also be configured to generate specific logs for troubleshooting purposes. Furthermore, the ```sysdiagnose``` tool offers a more comprehensive option for generating a wide range of logs, although much of it is limited to point-in-time data in relation to wireless, similar to wdutil.

By running ```sudo nohup /usr/bin/sysdiagnose -u &``` in the background, logs will be written to ```/var/tmp/<blah>.tar.gz```. For an *interactive* run (although not much interaction is required), you can execute ```sudo /usr/bin/sysdiagnose```, which will display 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 the Finder's Cmd+Shift+G shortcut. However, be cautious of the file sizes, which are approximately 300MB.
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