Check OSX Internet
An Overview of Internet Addressing
When using the Internet, you are assigned either a Public IPv4 address (e.g. 90.20.152.58) or an IPv6 address (e.g. 2000:9b3b:15ca:cfa9:3f03:7d03:9d8a:3082). You can verify this through https://test-ipv6.com/. However, for individuals who are not well-versed in technology, conveying these addresses or even mentioning MAC addresses like 80:f8:f6:6a:ba:0b can be prone to errors and quickly become complex. Moreover, this approach does not provide any historical data, especially from past occurrences of issues.
Navigating the Internet
When trying to reach a web page such as https://wolff-pagac.name, your computer initially connects to a DNS server to convert the host portion (wolff-pagac) combined with the Top Level Domain (name) of the URL to an IP address like 56.40.181.199. Your computer and browser transmits its type with all web requests, 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 Significance of Default Gateways
The default gateway is typically an automatically assigned address via DHCP. You receive a default gateway like 192.0.0.250 (although they usually end in .1 or .254 depending on the scope size), and this is where your computer transmits all its traffic to be routed onwards. We have an in-depth exploration of IPv6 on how-to-fix-ipv6-connectivity/, but you can verify on Mac or Linux using:
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 192.0.0.250 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:b167:1b0a:5817:8684%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): {207.75.67.103, 135.179.21.211}
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 80:f8:f6:6a:ba:0b
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 44:63:7e:2b:1e:3f
}
Fixing Connection Issues in Wired and Wireless Networks
When it comes to sending data to your router, you might encounter connectivity issues at the physical and data layer, whether you’re using a wired or wireless (Wi-Fi) medium.
Troubleshooting on Apple macOS / OSX
Regardless of whether you’re using OSX or macOS versions such as 10.13.3, 11.5.8, or 12.3.4, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a series of correlated values over time. This is where automated remote troubleshooting becomes especially valuable, particularly for teams that have embraced remote work and the Work From Anywhere (WFA) concept.
Utilizing Built-in Scripts
One beneficial tool available on OSX/macOS is the sudo wdutil info, which provides a dump to the CLI of current wireless settings and can be configured to generate specific troubleshooting logs. Additionally, the sysdiagnose tool can generate a wide range of logs, although much of it is only relevant to wireless settings at a specific point in time, similar to wdutil.
To run it in the background and write logs to /var/tmp/<blah>.tar.gz, you can use the command sudo nohup /usr/bin/sysdiagnose -u &. For an interactive run (which doesn’t involve much interaction), you can use sudo /usr/bin/sysdiagnose, but keep in mind that it will give a privacy warning. If not run in the background, it should open Finder in the correct location, or you can navigate to /var/tmp using Finder with Cmd+Shift+G. However, be cautious of the file sizes, which are roughly around 300MB.
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