DiagnOSe Apple Internet
Understanding Internet Addressing
When connecting to the Internet, you are assigned a Public IPv4 address such as 58.25.30.185 or an IPv6 address like 2000:2691:a933:7fb:4b6b:c965:e96b:7764. A simple way to verify this information is by visiting https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even referencing MAC addresses like 0c:a9:1d:f0:b8:d8, can be prone to errors and quickly becomes complicated. Moreover, this method lacks historical data, especially when troubleshooting past issues.
Navigating the Web
Accessing a website such as https://dach.info begins with contacting a DNS server to translate the host portion (dach) and the Top Level Domain (info) of the URL into an IP address, for example, 201.199.14.212. Each web request from your computer and browser also includes its type, for instance: 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
The default gateway is commonly an automatically configured address obtained via DHCP. Typically, the default gateway is assigned an address like 172.26.46.28 (often ending in .1 or .254 based on the scope size) and it serves as the point where your computer sends all traffic to be routed further. For a comprehensive insight into IPv6 and how to address connectivity issues, refer to our detailed guide how-to-fix-ipv6-connectivity/. Additionally, you can perform the same check 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 172.26.46.28 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:df0a:bb0b:a266:4ee8%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): {159.97.21.51, 158.66.138.176}
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 0c:a9:1d:f0:b8:d8
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 ed:0d:a5:60:ca:6e
}
Solve Issues with Wired or Wireless Connections
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.
Troubleshooting Tips for Apple macOS / OSX
No matter which version of OSX/macOS you’re running, whether it’s 10.11.6, 11.6.4, or 12.1.9, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting comes in handy, especially for teams that are into remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One very useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless settings to the CLI and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, though much of it is only related to wireless settings and is not continuous like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. If you prefer to run it interactively, you can execute 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. However, keep in mind that the file sizes are approximately 300MB.
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P.S. Tips For Remote Network and Client Support
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