How To Check Common Wifi Router Issues
Understanding Internet Protocol Addressing
When using the Internet, you are assigned a Public IPv4 address, such as 73.54.121.114, or an IPv6 address, like 2000:1dd0:5fec:8a67:5d17:93a4:f3df:39b0. You can verify this information by visiting https://test-ipv6.com/. However, it can be challenging for individuals who are not tech-savvy to convey these addresses accurately or to reference MAC addresses, like 33:7e:30:61:9c:4d, due to the potential for errors and complexity. Furthermore, it does not provide historical data, particularly relating to previous issues.
Navigating the Internet
Accessing a web page, such as https://wiegand.org, requires initially connecting to a DNS server to translate the host portion (wiegand) and the Top Level Domain (org) of the URL into an IP address, such as 223.65.69.172. Your computer and browser send their type with all web requests, for example:
Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36
Understanding the Significance of Default Gateways
Typically, your default gateway is an automatically configured address via DHCP. This gateway, such as 192.168.84.16, (although typically ending in .1 or .254 depending on the scope size), is where your computer sends all of its traffic to be routed onwards. For IPv6, an in-depth explanation is available at how-to-fix-ipv6-connectivity/. However, you can also check on Mac or Linux systems using the following command:
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 192.168.84.16 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 fe80:4550:6ca3:972:88cd%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): {194.148.37.78, 28.127.116.243}
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 33:7e:30:61:9c:4d
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 a7:9c:5d:02:bf:da
}
Resolving Issues with Wired and Wireless Connections
When it comes to transmitting 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’s macOS / OSX
Regardless of whether you are running OSX/macOS version 10.12.8, 11.5.5, or 12.1.8, 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 valuable, particularly for teams that adopt remote work and Work From Anywhere (WFA).
Useful Built-in Scripts
One useful tool on OSX/macOS is the sudo wdutil info command, which provides a dump to the CLI of the current wireless settings and can also generate specific logs for troubleshooting. Furthermore, the sysdiagnose tool can be used to generate a wide range of logs, although much of it pertains to wireless settings and is point-in-time only, similar to wdutil.
To run sysdiagnose in the background and generate logs in /var/tmp/<blah>.tar.gz, you can use sudo nohup /usr/bin/sysdiagnose -u &. If you prefer to run it interactively, you can use sudo /usr/bin/sysdiagnose, but be mindful of the large file sizes of about 300MB.
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