Support OSX Internet Connection
The Functioning of Internet Addressing
When using the Internet, individuals may be assigned a Public IPv4 address such as 124.213.226.58 or an IPv6 address like 2000:fae3:f107:54d7:8109:2cdb:c2ac:277c. It is possible to verify this information by visiting https://test-ipv6.com/. However, attempting to relay these addresses to individuals who are not technologically savvy, even mentioning MAC addresses like f4:e8:63:a0:0a:bf, can be prone to error and become complex quickly. Moreover, this method does not provide historical data, notably when past issues arise.
Navigating the Internet
In the process of accessing a webpage like https://muller.info, the initial step involves connecting to a DNS server to convert the host portion (muller) and the Top Level Domain (info) of the URL into an IP address such as 131.6.35.89. In fact, every web request originating from your computer and browser includes its type, for example: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A
Significance of Default Gateways
Typically, the default gateway is an address configured automatically through DHCP. A default gateway, such as 192.168.178.63 (usually ending in .1 or .254 based on the size of the scope), is where your computer dispatches all its traffic to be routed further. For IPv6, an in-depth explanation is available at how-to-fix-ipv6-connectivity/, while it can be verified on Mac or Linux using:
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 192.168.178.63 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:f77f:7ff:91ec:92bf%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): {130.104.172.133, 213.5.70.87}
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 f4:e8:63:a0:0a:bf
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 5f:b6:c6:45:99:1d
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting data to your router, you might be using either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple’s macOS / OSX
Regardless of the version of OSX/macOS you’re using, whether it’s 10.14.4, 11.3.9, or 12.1.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have embraced remote work and the Work From Anywhere (WFA) concept.
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info command, 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 produce 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 generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there isn’t much interaction), you can execute the command sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. It’s important to be aware of the file sizes, which are typically around 300MB.
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