Check Apple IP Settings
Understanding Internet Address Allocation
When using the internet, you are assigned a unique Public IPv4, such as 226.177.201.206, or an IPv6 address, like 2000:52a1:ab7a:2151:e358:2cc8:449e:c5db. You can verify this information by visiting https://test-ipv6.com/. However, for those who are not tech-savvy, conveying or referencing these addresses, as well as MAC addresses, such as 05:e0:00:b7:2d:d2, can be prone to errors and quickly become complex. Furthermore, this method does not provide any historical data, especially when previous issues occurred.
Navigating the World Wide Web
Accessing a website, such as https://tromp.org, involves initially contacting a DNS server to convert the host portion (tromp) combined with the Top Level Domain (org) of the URL into an IP address, such as 24.146.134.209. Your computer and browser always include 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)
The Significance of Default Gateways
Typically, your default gateway is an automatically configured address via DHCP, such as 192.0.0.91 (usually ending in .1 or .254 based on the scope size), which is the point where your computer directs all its traffic to be routed onwards. For troubleshooting IPv6 connectivity, we have provided a comprehensive guide at how-to-fix-ipv6-connectivity/, but you can also verify this on Mac or Linux by using the following command:
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 192.0.0.91 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 fe80:6b3a:71bb:6bb7:ca2c%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): {159.50.250.72, 155.84.117.235}
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 05:e0:00:b7:2d:d2
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 59:fd:aa:19:55:52
}
Resolve Connection Issues: Wired vs. Wireless
When it comes to transmitting data to your router, you may be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Effective Solutions for Apple macOS / OSX
Regardless of whether you are using OSX or macOS version 10.15.5, 11.3.8, or 12.2.4, there is a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes valuable, especially for teams that are embracing remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One valuable tool on OSX/macOS is sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although most are only point-in-time related to wireless, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, use sudo nohup /usr/bin/sysdiagnose -u &. For interactive use, run sudo /usr/bin/sysdiagnose, but be aware of the large file sizes of about 300MB.
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