Network toolkit
Subnet and address arithmetic, what your browser actually measured about this connection, and the exact ping, traceroute and dig command for your platform — since a browser cannot run those itself.
A browser cannot ping. No ICMP, no raw sockets, no way to set a TTL — a “ping” written in JavaScript is an HTTPS request wearing a costume. So this does the arithmetic, reads what your browser already measured loading this page, and writes the command for the rest. Nothing here contacts anything.
This connection
Reading.
Address or subnet
- Network
- 192.168.1.0/24
- Netmask
- 255.255.255.0wildcard 0.0.0.255
- Usable range
- 192.168.1.1 – 192.168.1.254
- Broadcast
- 192.168.1.255
- Addresses
- 256 total · 254 usable
Commands
Port 443 — HTTPS
Is it reachable
ICMP echo. Silence is not proof it is down — plenty of networks drop it.
ping -c 5 example.com
ping -c 5 -M do -s 1372 example.com
with fragmentation forbidden, to find the path MTU
What is the path
Each hop, and where the latency appears. Stars are usually a router declining to answer, not a break.
traceroute -q 1 example.com
mtr --report --report-cycles 20 example.com
continuous, and the better tool for intermittent loss
What does DNS say
The first thing to rule out, and the answer depends on who you ask.
dig +short example.com A
dig +short example.com AAAA
dig @1.1.1.1 +short example.com
asking a public resolver instead of yours
dig +trace example.com
the whole delegation chain, when the answer is wrong
Is port 443 open
Reachable and listening are different questions. This asks the second.
nc -vz example.com 443
curl -sS -o /dev/null -w '%{http_code} %{time_total}s\n' https://example.com/if it speaks HTTP
What is the certificate
Expiry and the name on it are behind a lot of “the site is down”.
openssl s_client -connect example.com:443 -servername example.com </dev/null 2>/dev/null | openssl x509 -noout -subject -issuer -dates