Troubleshoot Mcs Router Issues

Understanding Network Addressing

When using the Internet, you are assigned a unique Public IPv4 address such as 97.187.46.178 or an IPv6 address like 2000:3b7f:ba6e:4623:b246:5a3b:f366:e2d2. This information can be verified at https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or identifying MAC addresses like d2:f0:b4:81:e9:3c can be prone to errors and quickly becomes confusing. Furthermore, this method does not provide any historical data, particularly from the time when past issues occurred.

Navigating the World Wide Web

Accessing a website such as https://luettgen.com involves initially contacting a DNS server to convert the combination of the host portion (luettgen) and the Top Level Domain (com) of the URL into an IP address, for example 7.187.106.172. Whenever a web request is made, your computer and browser transmit their specifications, for instance:
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

By default, your computer is configured to utilize a gateway address that has been automatically assigned through DHCP. You are typically provided with a default gateway, such as 172.28.239.150 (often ending in .1 or .254 based on the scope size), to which your computer directs all its traffic for onward routing. Further information on configuring IPv6 can be found in our extensive guide on how-to-fix-ipv6-connectivity/. Additionally, you can verify this process on a Mac or Linux system 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  172.28.239.150    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:b179:a3b9:89d5:c943%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): {115.94.241.179, 40.224.12.189}
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 d2:f0:b4:81:e9:3c
  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 4c:8d:2d:78:32:5b
}

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Table 1.0 - Video Help