How Do You Troubleshoot Apple IP Settings
Understanding How Internet Addresses Function
When using the Internet, individuals may be assigned a Public IPv4 or IPv6 address. The former, such as 84.165.68.144, or the latter, as in 2000:ecf8:9fef:4e81:875c:b7fa:6b7f:ec74, can be verified on https://test-ipv6.com/. However, for those unfamiliar with technical jargon, conveying these addresses or even referring to MAC addresses like 5f:bc:a5:9a:d1:c2 can be prone to errors and become complex. Furthermore, this method does not offer historical data, especially relating to previous issues that have occurred.
Navigating the Internet
To access a webpage, such as https://rogahn.org, one must initially connect to a DNS server in order to translate the host portion (rogahn) combined with the Top Level Domain (org) of the URL to an IP address like 38.184.113.244. What’s more, the computer and browser send their type with every web request, for example: Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Significance of Default Gateways
Generally, the default gateway is automatically configured through DHCP and usually ends in .1 or .254, depending on the scope size. This is the location where all computer traffic is sent to be routed onwards. For those seeking further information on IPv6, refer to our comprehensive guide on how-to-fix-ipv6-connectivity/. Additionally, Mac or Linux users can verify their default gateway 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 192.0.0.187 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 fe80:2d7a:47da:af00:e325%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): {149.142.156.163, 10.50.69.102}
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 5f:bc:a5:9a:d1:c2
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 71:71:f6:4f:7d:83
}
Fixing Issues with Wired and Wireless Connections
When sending data to your router, you may utilize a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Techniques for Apple macOS / OSX
Whether you’re using OSX/macOS versions like 10.15.4, 11.5.8, or 12.3.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. Automated remote troubleshooting becomes essential, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very beneficial tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless related settings to the CLI and can also generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although many of them are point-in-time only in relation to wireless, just like wdutil.
To run sysdiagnose in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose, which 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 that the file sizes are approximately 300MB.
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