How Can I Support OSX IP Settings
Understanding How Internet Addressing Operates
When using the internet, you are assigned a Public IPv4 address, such as 182.205.162.89, or an IPv6 address, such as 2000:e5f1:8130:89f3:6f8:6db8:fa5:b6e5. You can verify these addresses at https://test-ipv6.com/. However, conveying these addresses to individuals who are not tech-savvy or referencing MAC addresses like 3e:48:90:f3:97:38 can quickly become complicated and error-prone. Moreover, it does not provide historical data, especially regarding past issues.
Navigating the World Wide Web
When attempting to access a webpage, such as https://labadie-kshlerin.biz, you first connect to a DNS server, which translates the host portion (labadie-kshlerin) along with the URL’s Top Level Domain (biz) to an IP address like 81.117.228.11. Additionally, your computer and browser automatically include its type in 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)
Significance of Default Gateways
Typically, your default gateway is an address that is automatically configured through DHCP. You receive a default gateway, such as 192.168.207.139 (usually ending in .1 or .254 depending on the scope size), and this is where your computer sends all its traffic to be routed onwards. For a thorough exploration of IPv6, you can read our article on how-to-fix-ipv6-connectivity/. Additionally, you can verify this on Mac or Linux using:
your command here
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 192.168.207.139 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:c9ac:6d36:eab0:57f6%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): {62.166.101.42, 61.213.103.119}
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 3e:48:90:f3:97:38
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 65:5e:d3:12:b2:93
}
Troubleshooting and Resolving Connectivity Issues
When it comes to the physical and data layer, you may find yourself using either a wired or wireless (Wi-Fi) medium to transmit data to your router.
Resolving Issues on Apple macOS / OSX Systems
Regardless of the version of OSX/macOS you are using, whether it’s 10.15.4, 11.0.1, or 12.1.7, there are various tools available for troubleshooting. However, these manual actions and scripts do not provide a set of correlated values over time. This is where automated remote troubleshooting becomes invaluable, particularly for teams that have adopted remote work and Work From Anywhere (WFA) practices.
Utilizing Built-in Scripts for Assistance
One extremely useful tool on OSX/macOS is the sudo wdutil info command, which produces a dump of current wireless settings to the CLI and can be configured to generate specific logs for troubleshooting. Additionally, the sysdiagnose tool can be used to generate a wide range of logs, albeit many of them providing only point-in-time information related to wireless, similar to wdutil.
Running sudo nohup /usr/bin/sysdiagnose -u & in the background will generate logs in /var/tmp/<blah>.tar.gz for you. If you prefer to run it interactively (although there isn’t much interaction), you can run sudo /usr/bin/sysdiagnose and it will display a privacy warning. When not run in the background, it should open Finder in the correct location, or alternatively, you can navigate to /var/tmp or use Finder with Cmd+Shift+G to direct Finder to the path. Keep in mind that the file sizes are approximately 300MB.
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