How To Check OSX No-access
Demystifying Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 135.228.26.228, or an IPv6 address, like 2000:3af1:3284:f88:a113:2cdc:b328:1209. You can verify this information by visiting https://test-ipv6.com/. However, conveying these addresses to those who are not tech-savvy or even referring to MAC addresses, such as 19:24:d3:9b:26:c1, can be prone to errors and quickly become complex. Moreover, this does not provide any historical data, particularly when past issues occurred.
Navigating the World Wide Web
Accessing a web page, like https://koss.org, involves an initial request to a DNS server to translate the host portion (koss) combined with the Top Level Domain (org) of the URL into an IP address, such as 182.11.20.194. Every web request sent from your computer and browser includes the user-agent 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
Understanding the Significance of Default Gateways
Your default gateway is typically an automatically configured address via DHCP. It is a default gateway, like 192.168.57.243 (usually ending in .1 or .254, depending on the scope size), where your computer sends all of its traffic to be routed onwards. For IPv6, you can explore further in our detailed article on how-to-fix-ipv6-connectivity/, or verify on Mac or Linux 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 192.168.57.243 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 fe80:457b:ed3:dd94:fdd8%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): {245.111.198.5, 86.70.144.118}
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 19:24:d3:9b:26:c1
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 71:84:e8:72:11:e7
}
Fixing Connectivity Issues With Wired and Wireless Networks
When it comes to reaching your router, you might be utilizing either a wired or wireless (Wi-Fi) connection at the physical and data layer.
Solutions for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are running, whether it’s 10.11.9, 11.1.5, or 12.1.6, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a set of correlated values over time, which is where automated remote troubleshooting becomes invaluable, especially for teams that have adopted remote work and the Work From Anywhere (WFA) approach.
Useful Built-in Tools for Troubleshooting
One of the most useful tools for OSX/macOS users is sudo wdutil info, which provides a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting purposes. Another tool, sysdiagnose, offers a more comprehensive set of logs, although many are only relevant to wireless settings, similar to wdutil.
To run it 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, the command sudo /usr/bin/sysdiagnose can be used, but be cautious of the file sizes, which are typically around 300MB.
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