How Do You Fix Mac IP Settings
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 or an IPv6 address, such as 153.115.239.63 or 2000:b1a8:970a:713e:9c13:a67c:3131:2d13. You can verify this information at https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even referencing MAC addresses like ea:9a:53:23:60:82, can be prone to errors and can become complex. Moreover, this method does not provide any historical data, especially regarding past issues.
Navigating the World Wide Web
When trying to access a website such as https://schuppe-smitham.com, your browser first communicates with a DNS server to convert the host portion (schuppe-smitham) combined with the Top Level Domain (com) of the URL into an IP address, such as 92.56.51.39. Your computer and browser also transmit their type with all web requests, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
The Significance of Default Gateways
Default gateways are typically automatically configured addresses through DHCP. You are assigned a default gateway, such as 10.88.69.46 (usually ending in .1 or .254 based on the scope size), which is where your computer sends all its traffic to be routed onward. For IPv6, you can refer to our in-depth guide on how-to-fix-ipv6-connectivity/. Alternatively, you can verify this information on Mac or Linux 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 10.88.69.46 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:b1d9:edad:f117:8467%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): {161.158.244.36, 178.168.175.4}
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 ea:9a:53:23:60:82
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 74:a6:02:59:96:bf
}
Diagnosing and Resolving Connectivity Issues
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.
Tips for Resolving Issues on Apple Operating Systems
Regardless of whether you’re running MacOS or OSX, whether it’s version 10.13.6, 11.3.2, or 12.2.9, there is a variety of troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time, making automated remote troubleshooting particularly valuable for teams embracing remote work and Work From Anywhere (WFA).
Useful Built-in Tools
A highly useful tool for 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 logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a comprehensive set of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
To run the sysdiagnose tool in the background and write logs to /var/tmp/<blah>.tar.gz, use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run, you can use sudo /usr/bin/sysdiagnose, but beware of file sizes of approximately 300MB.
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