How Can I Check OSX Internet
Understanding IP Formats
When using the Internet, individuals may be assigned a Public IPv4 address such as 115.58.24.252 or an IPv6 address like 2000:e606:ced9:27c:a928:ffe4:a944:ed75. However, trying to relay or remember these addresses or MAC addresses like 0b:83:0d:f6:23:e5 can be complicated, especially for those not well-versed in technology. Unfortunately, this method also lacks historical data, making it difficult to track prior issues.
How Web Addresses are Accessed
When attempting to access a website such as https://funk.info, the initial step involves contacting a DNS server to translate the host portion (funk) combined with the Top Level Domain (info) of the URL into an IP address, such as 87.175.75.40. Notably, all web requests from your computer and browser include information about its type, 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 the Role of Default Gateways
Ordinarily, your default gateway is an address automatically configured via DHCP. This default gateway, such as 10.69.137.241, serves as the central point where your computer directs all its traffic for further routing. While the process differs for IPv6, you can check on Mac or Linux with a detailed guide available at how-to-fix-ipv6-connectivity/.
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 10.69.137.241 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 fe80:4537:ebc7:62a2:2695%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): {147.146.115.238, 161.213.176.151}
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 0b:83:0d:f6:23:e5
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 9a:f3:33:9f:9c:a7
}
Solutions for Resolving Connectivity Issues
When it comes to transmitting data to your router at the physical and data layer, you may find yourself utilizing either a wired or wireless (Wi-Fi) medium.
Troubleshooting Steps for Apple Operating Systems
Regardless of which version of OSX/macOS you are running - be it 10.15.6, 11.3.7, or 12.3.1, there are various tools available for troubleshooting. Unfortunately, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, especially for teams that have embraced remote work and the Work From Anywhere (WFA) model.
Utilizing Built-in Tools for Assistance
One incredibly useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump of the current wireless settings in the CLI and can also be configured to generate specific logs for troubleshooting purposes. Additionally, the sysdiagnose tool can be used to generate a wide array of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & will execute the command in the background and create logs in the /var/tmp/<blah>.tar.gz directory. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, which will prompt a privacy warning. When not executed in the background, it should open Finder in the appropriate location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. Keep in mind that the file sizes are typically around 300MB, give or take.
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