Support Mac IP Settings
Explaining Internet Addressing
When using the Internet, you’re assigned a Public IPv4 or IPv6 address, such as 162.215.198.164 or 2000:eb44:9fd5:3a4a:a400:ceb9:5607:2484. You can verify these addresses at https://test-ipv6.com/. However, communicating these addresses, especially for those not well-versed in technology, and even referencing MAC addresses like c7:58:b8:5c:6c:b3, can be prone to errors and become complex quickly. Additionally, this method does not provide any historical data, particularly for past issues.
Navigating the World Wide Web
In order to access a website such as https://mann.io, your computer first contacts a DNS server to convert the host portion (mann) combined with the Top Level Domain (io) of the URL into an IP address, like 92.22.156.177. Your computer and browser also include their type in all web requests, for example: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
The default gateway is usually an address that is automatically configured via DHCP. This address, such as 10.16.68.151 (although it typically ends in .1 or .254 depending on the scope size), is where your computer sends all its traffic to be routed onwards. For IPv6, you can find a detailed guide on how-to-fix-ipv6-connectivity/, and on Mac or Linux you can check 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 10.16.68.151 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 fe80:2f6e:642c:4807:a800%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): {168.217.92.216, 88.255.149.163}
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 c7:58:b8:5c:6c:b3
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 25:38:f0:81:dd:01
}
Fixing Connectivity Issues for Wired or Wireless Network
When it comes to transmitting data to your router, you may be utilizing a wired or wireless (Wi-Fi) medium at the physical and data layer.
Resolving Problems on Apple macOS / OSX
Regardless of the version of OSX/macOS you are using, whether it’s 10.12.8, 11.5.5, or 12.0.4, there are multiple 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 beneficial, especially for teams that are involved in remote work and Work From Anywhere (WFA).
Useful Built-in Tools
One extremely useful tool on OSX/macOS is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can also be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is related to wireless only and is not continuous like wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute it in the background and write logs to /var/tmp/<blah>.tar.gz. For interactive use, you can run sudo /usr/bin/sysdiagnose, but be mindful of the large file sizes, around 300MB more or less.
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P.S. Tips For Remote Network and Client Support
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