How Do You Fix Mac Connectivity
Understanding Internet Addressing
When using the Internet, you are assigned a unique IPv4 or IPv6 address, such as 236.90.227.195 or 2000:ea49:b5d8:9da8:18e5:11cd:218a:4731. You can verify this information by visiting https://test-ipv6.com/. However, explaining and using these addresses or MAC addresses like 46:24:f4:3f:49:d2 can become complex, especially for those without technical expertise. Furthermore, this method does not provide any historical data, particularly when past issues occurred.
Navigating the World Wide Web
When accessing a website such as https://huel.io, your computer first connects to a DNS server to convert the website’s host (huel) and Top Level Domain (io) to an IP address, like 84.102.135.33. Moreover, your computer and browser include their specifics in all web requests, 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
The default gateway is usually automatically assigned through DHCP and manifests as an address like 172.22.218.141 (typically ending in .1 or .254, depending on the scope size). This is the point where your computer forwards all its traffic for routing. For IPv6, we offer an in-depth guide at how-to-fix-ipv6-connectivity/, or you can verify 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 172.22.218.141 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 fe80:2241:13ef:3879:5a7c%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): {96.80.98.174, 149.9.166.113}
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 46:24:f4:3f:49: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 15:4e:81:ee:0f:de
}
Troubleshooting Issues with Wired and 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.
Effective Solutions for Apple macOS / OSX
Regardless of whether you are using OSX/macOS version 10.14.3, 11.5.2, or 12.0.4, there are various tools available for troubleshooting. However, despite the availability of manual actions and scripts, they do not provide a series of correlated values over time. This is where automated remote troubleshooting comes in handy, particularly for teams that are adopting remote work and Work From Anywhere (WFA).
Utilizing Built-in Scripts for Assistance
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 create specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, although much of it is only relevant to wireless settings, similar to 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 sudo /usr/bin/sysdiagnose, but beware of the large file sizes, which are approximately 300MB or more.
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