How Can I Fix OSX Internet
Understanding Internet Address Allocation
When using the Internet, you may receive a Public IPv4 address such as 36.66.29.254 or an IPv6 address like 2000:1a13:2deb:4a61:185e:c16d:d9:e61. The website https://test-ipv6.com/ can verify this for you. However, explaining these addresses to those not well-versed in technology can be challenging, especially when dealing with MAC addresses like 94:c0:5d:c1:9a:8a. Furthermore, historical data is not provided, which is particularly important when addressing past issues.
Navigating the World Wide Web
In order to access a website such as https://wehner.net, you first consult a DNS server to convert the host segment (wehner) in combination with the Top Level Domain (net) of the URL into an IP address like 230.5.64.220. Every web request from your computer and browser contains its type, such as 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
Your default gateway is typically an automatically assigned address through DHCP. It could be a default gateway such as 192.168.208.225 (often ending in .1 or .254 depending on the scope size), which is where your computer directs all of its traffic to be forwarded. For details on IPv6, a comprehensive guide is available at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux, the status can be checked 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 192.168.208.225 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 fe80:37ee:dd32:869:aa97%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): {57.128.221.12, 120.246.181.123}
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 94:c0:5d:c1:9a:8a
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 e8:c2:27:16:b7:6f
}
Fixing Issues with Wired and Wireless Connections
When it comes to transmitting data towards your router, you might be using a wired or wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting on Apple macOS / OSX
No matter which version of OSX/macOS you’re running—whether it’s 10.11.9, 11.0.9, or 12.0.2—there are various tools available for troubleshooting. However, these manual actions and scripts fail to provide a set of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for teams that embrace remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
A very helpful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of current wireless-related 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 only relevant to wireless settings, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (even though there isn’t much interaction), you can use sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to point Finder to the path. Just be mindful of the file sizes, which are usually around 300MB.
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