How To Understand OSX No-access
Understanding Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 115.190.176.189, or an IPv6 address, like 2000:340a:2273:331:d969:278c:aebe:ae5a. Verify your address at https://test-ipv6.com/. However, conveying and managing these addresses, as well as MAC addresses like 35:af:77:c7:1e:6f, can be error-prone and complex, especially for those not well-versed in technology. Furthermore, this method lacks historical data for previous issues.
Navigating the World Wide Web
When accessing a website, such as https://dach.io, your computer initially contacts a DNS server to convert the host portion (dach) combined with the Top Level Domain (io) of the URL to an IP address, such as 99.129.117.97. Additionally, your computer and browser communicate their type with each web request e.g. 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 via DHCP, such as 192.168.247.39 (though typically ending in .1 or .254 depending on the scope size). This is where your computer directs all its traffic to be routed onwards. For IPv6, you can refer to our comprehensive guide on how-to-fix-ipv6-connectivity/ or check on Mac or Linux with 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 192.168.247.39 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 fe80:26eb:3d26:dba3:d4fb%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): {201.215.222.174, 114.17.30.249}
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 35:af:77:c7:1e:6f
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 58:4f:c5:64:0d:9e
}
Solutions for Wired and Wireless 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.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of whether you are using OSX or macOS versions such as 10.11.8, 11.3.7, or 12.1.3, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. For remote troubleshooting, especially for teams that embrace remote work and Work From Anywhere (WFA), automated solutions become more valuable.
Useful Built-in Scripts
A helpful tool on 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 wide variety of logs, although much of the information is only point-in-time in relation to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will write logs to /var/tmp/<blah>.tar.gz. For interactive use, you can run sudo /usr/bin/sysdiagnose to trigger a privacy warning, and then navigate to the correct location in Finder or use the path /var/tmp with Cmd+Shift+G in Finder. However, be cautious of the file sizes, which can be around 300MB or more.
Possibly Helpful Videos
P.S. Tips For Remote Network and Client Support
Digital work requires reliable connectivity. Whether for low latency or regular data streams, Wi-Fi, DNS, and network issues cause teams to lose time and productivity. Even worse is when support teams waste time trying to recreate and isolate issues! See how PanSift saves time, money, and frustration on all sides with instant remote troubleshooting 🏠🏝🛰.
