Test Mac Issues
Understanding the Functioning of Internet Addressing
When using the Internet, you are assigned a Public IPv4 or IPv6 address. Checking your IP address can be done through https://test-ipv6.com/. However, conveying these addresses to non-technical individuals, or even mentioning MAC addresses, such as 9b:19:8e:f3:cb:cf, can be prone to errors and can become complex quite quickly. Moreover, historical data is not provided, particularly for past issues.
Navigating the World Wide Web
In order to access a website like https://von-ohara.net, your computer first contacts a DNS server to convert the host portion (von-ohara) combined with the Top Level Domain (net) of the URL into an IP address, such as 233.159.1.180. Every web request from your computer and browser contains information about its type, for example: Opera/9.80 (X11; Linux i686; Ubuntu/14.10) Presto/2.12.388 Version/12.16
Understanding the Significance of Default Gateways
Commonly, your default gateway is an automatically assigned address via DHCP. This default gateway, like 10.233.218.82 (usually ending in .1 or .254 depending on the scope size), is where your computer forwards all its traffic to be routed further. For IPv6, a detailed explanation is available in our blog: how-to-fix-ipv6-connectivity/ but it can also be checked on Mac or Linux.
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 10.233.218.82 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:b50d:a63:ef60:f8b0%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): {171.131.224.61, 129.99.13.203}
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 9b:19:8e:f3:cb:cf
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 1f:92:f6:ad:6c:17
}
Resolving Connectivity Issues in Wired and Wireless Networks
When it comes to sending data to your router, you may be utilizing either a wired or a wireless (Wi-Fi) medium at the physical and data layer.
Troubleshooting Tips for Apple macOS / OSX Users
Regardless of the version of OSX/macOS you are currently using, whether it’s 10.11.2, 11.6.5, or 12.3.3, 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 particularly valuable, especially for remote teams and those practicing Work From Anywhere (WFA).
Utilizing Built-in Tools for Assistance
One particularly useful 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. Another comprehensive tool is the sysdiagnose, which can generate a wide range of logs, although much of it is only relevant at a specific point in time in relation to wireless, similar to wdutil.
To run sudo nohup /usr/bin/sysdiagnose -u & in the background and write logs to /var/tmp/<blah>.tar.gz. For those who prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, although it will prompt a privacy warning. When not running in the background, it should open Finder in the correct location, or you can navigate to /var/tmp or use Finder with Cmd+Shift+G to locate the path. However, bear in mind that the file sizes are approximately 300MB or more.
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