Networking, one packet at a time
Free animated guides to how network protocols really work. Every mechanism plays out step by step, every configuration line is explained, and the exam notes show what CCNA, CCNP and CCIE expect.
| Frame | dst MAC | src MAC | TTL |
|---|---|---|---|
| 1 | R1 Gi0/0 | PC-A | 64 |
| 2 | R2 Gi0/1 | R1 Gi0/1 | 63 |
| 3 | Server | R2 Gi0/0 | 62 |
Inside all three: IP 10.1.1.10 to 10.2.2.20.
PC-A sends a packet to 10.2.2.20, on another subnet. So it puts the packet in a frame for its default gateway: the destination MAC is R1’s, learned through ARP.
Inside every guide
Animations you can step through
Each mechanism runs on a small topology. Pause it, go back a step or slow it down.
Configuration, line by line
Every line of configuration or code is explained, and highlighted when the animation uses it.
Simulators
Where one setting changes the outcome, you change it yourself and see what happens.
Exam notes
Notes in five colours, and a map of where each topic appears in CCNA, CCNP and CCIE.
All topics
50 guides in 8 chapters
- LAN & switching
- Routing
- IP services
- VPNs & tunnels
- Overlays & fabrics
- Security & access
- Monitoring & operations
- Automation & programmability
Continue where you left off
LAN & switching
How frames find their way inside a building: VLANs, loops, bundles and the layout of the campus.
- Unicast, broadcast, multicast, anycastWho receives the packet and who makes the copies15 sections
- VLANs and trunksSeveral networks on the same cable12 sections
- STPPhysical redundancy, a single logical path13 sections
- EtherChannelMultiple links, a single port12 sections
- Enterprise network architectureWho does what, and why there15 sections
Routing
How routers learn paths, pick the best one and forward packets without asking the CPU.
- OSPFThe same map for everyone, each with its own path16 sections
- EIGRPBackup routes computed before the failure18 sections
- BGPFrom the first session to EVPN19 sections
- MulticastOne stream, replicated only where it is requested18 sections
- CEFHow a packet gets from the RIB to the wire without touching the processor12 sections
- VRFSeveral routing tables, a single router14 sections
IP services
The services every network runs: address translation, time, quality of service and probes.
VPNs & tunnels
Packets inside packets: encapsulation, encryption and hub-and-spoke designs.
Overlays & fabrics
Labels, VNIs and controllers: MPLS, VXLAN/EVPN, LISP, SD-Access and SD-WAN.
- MPLSLabels instead of addresses, services on top of labels17 sections
- VXLANL2 over L3, with EVPN as the control plane15 sections
- EVPNBGP says where every host is, VXLAN takes it there16 sections
- LISPWho you are and where you are, kept apart15 sections
- SD-AccessThe campus fabric, the control, data and policy planes16 sections
- SD-WANAn encrypted overlay, run by controllers16 sections
Security & access
Who gets onto the network, what gets through and how the network spots trouble.
- ACLsWhat gets through, what doesn't, and why13 sections
- Zone-Based FirewallZones, sessions and what gets back in13 sections
- RADIUSWho you are, what you're allowed to do, what you did15 sections
- NACWho gets onto the port, with what proof and with what rights17 sections
- IBNS and 802.1XWho gets into the network and with what rights13 sections
- StealthwatchFrom NetFlow records to alarms and quarantine15 sections
Monitoring & operations
Logs, counters, flows, mirrored traffic, user-experience probes and the systems that run a service provider.
- SyslogThe logging agent, from the event to the server15 sections
- SNMPWhat the manager asks, what the device answers and what it says on its own15 sections
- NetFlowWho talks to whom, how much and when15 sections
- SPAN, RSPAN and ERSPANA copy of the traffic, without stopping it13 sections
- Assurance agentsWho measures the user's experience, and from where15 sections
- OSS/BSSFrom the customer's order to the configuration on the device and back to the invoice15 sections
Automation & programmability
Data formats, APIs, models and the tools that push configuration for you.
- JSONThe text all network APIs speak14 sections
- XMLTags, the tree and the procedure at the NETCONF counter14 sections
- YANGThe model behind network automation15 sections
- REST APIsWhat you ask for, what you get and why16 sections
- PostmanFrom an HTTP request to a test suite in CI15 sections
- NETCONFXML operations over SSH, on YANG models16 sections
- RESTCONFThe router's datastore, over HTTP16 sections
- Agent-based vs agentlessWho initiates, who holds the state15 sections
- AnsibleDesired state, applied without an agent16 sections
- PuppetWho asks, who compiles, who changes16 sections
- ChefHow the desired state reaches every node15 sections
- SaltThe master publishes, the minion decides, executes and reports16 sections
- EEMThe agent that reacts on the device15 sections
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