Network Tools
Test reachability and routing from the public internet: ping a host for latency and packet loss, trace the path with traceroute, check which TCP ports are open, and find out who operates an IP address.
The probes run from our servers, so they show what the outside world sees, which is often different from what you see inside your own network or VPN.
5 free network tools
Guides: Network Protocols
- IPv6 for People Who Know IPv4Address notation and the /64 rule, link-local and ULA and GUA, SLAAC vs DHCPv6, no NAT and what replaces it, NDP instead of ARP, dual-stack, and the firewall implications.
- 802.1Q VLANs ExplainedVLAN tags in the Ethernet frame, access vs trunk ports, the native VLAN, inter-VLAN routing, configuring tagged interfaces on Linux, and the security gotchas (VLAN hopping).
- VXLAN and Overlay NetworksWhy overlays exist, VXLAN encapsulation (VNI, VTEP, UDP 4789), MTU implications, multicast vs unicast/EVPN control planes, and how container/cloud networks use it under the hood.
- TCP Congestion Control BasicsSlow start, congestion avoidance, fast retransmit/recovery, the difference between loss-based (CUBIC) and model-based (BBR) control, bufferbloat, and picking an algorithm on Linux.
- VRRP and keepalived for Gateway/Service FailoverHow VRRP shares a virtual IP between routers, master election and priority, keepalived config for a floating VIP, adding health checks and LVS, and split-brain / ARP gotchas.
- DNS over TLS and DNS over HTTPSWhy plain DNS is a privacy and integrity problem, how DoT (port 853) and DoH (443) differ, where each fits, running a resolver with DoT upstream, and the enterprise visibility trade-off.
Checking a whole domain? The Super Scanner runs every DNS, email, website and security check at once and gives one score.