Fix Mcs Connectivity
Understanding Internet Addressing
When connecting to the Internet, you are assigned a unique identifier, such as the Public IPv4 address 88.46.129.111 or the IPv6 address 2000:9688:25e6:1900:cfa2:96ae:6a6:91f6. These addresses can be verified at https://test-ipv6.com/. However, the process of communicating these addresses and MAC addresses such as 6c:a9:a5:b4:73:47 can be error-prone and complex, especially for those who are not tech-savvy. Furthermore, there is often a lack of historical data regarding past issues.
Navigating the World Wide Web
When accessing a website, such as https://weber-schiller.info, the initial step involves querying a DNS server to translate the domain name (weber-schiller) and the Top Level Domain (info) into an IP address, such as 159.194.48.187. The web requests from your computer and browser also include information about their 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
The default gateway is typically assigned through DHCP and is usually an automatically configured address, such as 192.0.0.18 (commonly ending in .1 or .254 based on the scope size). This gateway serves as the central point through which your computer forwards all its outgoing traffic. For IPv6, detailed information on troubleshooting can be found at how-to-fix-ipv6-connectivity/. Additionally, on Mac or Linux systems, the default gateway can be verified 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 192.0.0.18 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:e9b:2c4a:c69c:71a8%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): {182.236.67.25, 29.156.37.159}
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 6c:a9:a5:b4:73:47
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 c5:5d:4d:ff:a2:0c
}
Resolving Issues with Wired or Wireless Connections
When it comes to transmitting data to your router, you could be using 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 running OSX/macOS version 10.13.5, 11.2.3, or 12.1.3, there are various troubleshooting tools available. Unfortunately, these manual actions and scripts do not provide a set of interconnected values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have embraced remote work and Work From Anywhere (WFA).
Useful Built-in Utilities
One extremely helpful tool on OSX/macOS is sudo wdutil info, 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 generate a wide range of logs in a more comprehensive manner. However, many of these logs are only relevant to the wireless connection, similar to wdutil.
To run sysdiagnose in the background and have the logs written to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use the command sudo /usr/bin/sysdiagnose. Keep in mind that the file sizes can be around 300MB.
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