Interactive Simulators
Networking concepts only make sense when you can move them. These run in your browser — slide a CIDR mask, send a frame through a trunk, watch STP converge. No installs, no Packet Tracer required.
CDP / LLDP Neighbor Discovery
Three devices in a chain (two Cisco + one Aruba). Toggle CDP or LLDP on the timeline and watch the neighbor tables build up with real show cdp neighbors / show lldp neighbors output.
Open simulator →DHCP DORA Simulator
Walk through Discover, Offer, Request, Ack step by step, with source/destination IPs, UDP ports, and options for each packet. Toggle the ip helper-address relay scenario to see how cross-subnet DHCP works.
Open simulator →EIGRP Successor / FS Simulator
Live EIGRP topology table with three paths to one destination. Shows the Feasibility Condition (RD < FD) picking the Feasible Successor. Fail the Successor path and watch DUAL install the FS instantly with zero recomputation.
Open simulator →EtherChannel LACP Simulator
Two switches, four cables. Pick a channel-group mode on each side and watch whether the bundle forms — with a real show etherchannel summary printout per switch and STP behavior visualized on the links.
Open simulator →Extended ACL
Practice extended ACL syntax: protocol + source + destination + port. Build the entry, apply it, then run packets through and see which rule matches. Console output, ACL hit counters, and worked traffic scenarios.
Open simulator →HSRP Failover Simulator
Two routers share a virtual IP + virtual MAC via HSRP. Adjust priorities, toggle preempt + WAN tracking, then kill a router or its uplink — watch the standby take over and clients keep their gateway with no ARP change.
Open simulator →IPv6 SLAAC Boot Simulator
A host boots on an IPv6 network. Watch it derive its link-local from the MAC via EUI-64 (including the U/L-bit flip), send Router Solicitation, receive the RA, build its global address, then run Duplicate Address Detection.
Open simulator →NAT / PAT Translation Walkthrough
Send packets from inside hosts to the internet and watch R1 rewrite the source IP (and port for PAT/overload), build the translation table live, then untranslate the reply. Static NAT, dynamic pool, and the classic ip-nat-inside/outside + ACL misconfig scenarios included.
Open simulator →OSPF Neighborship
Cisco-IOS-style neighbor state machine. Click Advance Handshake, watch Hello/DBD/LSR/LSU envelopes move between R1 and R2, with live IOS syslog, packet analyzer, and show commands. Includes Hello mismatch + ACL block + MTU mismatch troubleshooting scenarios.
Open simulator →Route Summarization / CIDR Aggregation
Enter up to four contiguous subnets and see the shortest CIDR block that covers them all — plus a bit-by-bit walkthrough of exactly why the summary prefix is that length, and a warning when subnets don't line up cleanly.
Open simulator →Spanning Tree (STP)
Three switches in a triangle. Change the bridge priorities to elect any root, watch each port become Root / Designated / Blocked, then fail a link and watch the blocked port unblock and the tree reconverge in real time.
Open simulator →Standard ACL
Configure a numbered or named standard ACL on an interface, send test traffic, see permit/deny verdicts and matching IOS syslog. Includes implicit deny visualization and common-pitfall scenarios.
Open simulator →Subnetting Visualizer
Practice quiz on top. Below: slide a CIDR prefix and watch network, broadcast, host range, masks and the 32-bit boundary update live. VLSM splitter included.
Open simulator →TCP Handshake Simulator
Walk through a full TCP connection — SYN, SYN-ACK, ACK to open; a single byte of data; then the four-way FIN close. Sequence + acknowledgment numbers update live; both endpoints' states advance through the classic state machine (LISTEN → SYN-RECEIVED → ESTABLISHED → FIN-WAIT → TIME-WAIT).
Open simulator →VLAN + Trunk Frame Walkthrough
Send a frame from one PC to another across a switch trunk. Watch the 802.1Q tag get added on ingress and stripped on egress, with native VLAN and inter-VLAN scenarios included.
Open simulator →Want this drilled into reflex?
1:1 mentorship around real labs, live debugging, and US interview prep. Free first session.