Troubleshoot Mac No-access
Understanding Internet Addressing
When using the Internet, your device may have a unique Public IPv4 address, such as 169.12.29.137, or an IPv6 address like 2000:a8f:5f0b:8426:7814:6870:c840:9736. You can verify this information by visiting https://test-ipv6.com/. However, these addresses, along with MAC addresses like 9c:dc:53:61:27:db, can be challenging for individuals without technical expertise to communicate accurately.
Moreover, this approach lacks historical information, especially when recurring issues arise.
Navigating the Internet
Accessing a website like https://kohler.name involves interacting with a DNS server to convert the host portion (kohler) and the Top Level Domain (name) of the URL into an IP address, such as 120.73.99.111. When making web requests, your computer and browser also share their information, for example:
Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Understanding Default Gateways
Typically, your default gateway is automatically assigned through DHCP. It usually ends with .1 or .254, depending on the scope size, and your computer directs all its traffic to this gateway for onward routing. For IPv6, detailed instructions can be found in our blog post on how-to-fix-ipv6-connectivity/. On Mac or Linux, you can check this using:
<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 10.162.139.90 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 fe80:13c2:7b69:ecc1:a79f%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): {199.120.57.39, 148.217.234.75}
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 9c:dc:53:61:27:db
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 af:d5:40:79:d9:e3
}
Resolving Wired and Wireless Connectivity Issues
When it comes to sending data to your router, the choice of using a wired or wireless (Wi-Fi) medium at the physical and data layer can make a big difference.
Tips for Apple macOS / OSX Users
No matter if you are using OSX/macOS version 10.14.8, 11.5.1, or 12.3.5, there are various troubleshooting tools available. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes particularly useful, especially for remote work and Work From Anywhere (WFA) teams.
Utilizing Built-in Scripts
One valuable tool on OSX/macOS is the sudo wdutil info, 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 array of logs related to wireless, albeit mostly point-in-time.
To run it in the background and generate logs, use sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively, use sudo /usr/bin/sysdiagnose, keeping in mind the large file size of about 300MB.
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P.S. Tips For Remote Network and Client Support
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