Check Mac Connectivity
Demystifying Internet Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 177.67.91.48, or an IPv6 address, like 2000:aab4:6f2d:e653:6241:f1d0:eaa4:a2b4. You can easily check this at https://test-ipv6.com/. However, explaining these addresses, and even MAC addresses like 52:c4:aa:f1:b5:6d, to individuals not well-versed in technology can become cumbersome and error-prone. Moreover, this method lacks historical data, especially from past issues.
Navigating the World Wide Web
When accessing a web page, such as https://wilderman.name, you first contact a DNS server to convert the host portion (wilderman) and the Top Level Domain (name) of the URL into an IP address, for example, 149.198.205.76. Your computer and browser also include its type in all web requests, like Mozilla/5.0 (compatible; MSIE 9.0; AOL 9.7; AOLBuild 4343.19; Windows NT 6.1; WOW64; Trident/5.0; FunWebProducts)
Exploring the Significance of Default Gateways
The default gateway is typically an address automatically configured via DHCP. It often ends in .1 or .254 depending on the scope size, such as 192.168.149.80. This is the point where your computer forwards all its traffic to be routed further. For IPv6, you can delve deeper into this topic in our article how-to-fix-ipv6-connectivity/, and for Mac or Linux, you can verify using 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 192.168.149.80 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:aeac:bb22:456a:dbf7%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): {21.248.127.159, 33.120.44.43}
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 52:c4:aa:f1:b5:6d
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 ac:38:a4:9c:bb:87
}
Fixing Network Connectivity Issues
Whether you are using a wired or wireless connection, the physical and data layer play a crucial role in transmitting data to your router.
Troubleshooting Tips for Apple macOS / OSX
Regardless of whether you are running OSX/macOS version 10.13.1, 11.0.3, or 12.3.2, 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 invaluable, especially for remote teams and Work From Anywhere (WFA) environments.
Helpful Built-in Scripts
A useful tool on OSX/macOS is sudo wdutil info, which provides wireless-related settings and can be configured to generate specific troubleshooting logs. Furthermore, the sysdiagnose tool can generate a wide range of logs, though many are only relevant to wireless settings, similar to wdutil.
To run sysdiagnose in the background, use the command sudo nohup /usr/bin/sysdiagnose -u &, which will write logs to /var/tmp/<blah>.tar.gz. For an interactive (though not highly interactive) run, use the command sudo /usr/bin/sysdiagnose with a privacy warning. When not run in the background, it will open Finder in the correct location, or you can navigate to /var/tmp using Finder or Cmd+Shift+G. Note that the file sizes are approximately 300MB.
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P.S. Tips For Remote Network and Client Support
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