Topics

What each topic covers

1. 01Models and how networks work 46

   OSI model layer by layer and what lives at each layer, TCP/IP model and how it maps to OSI, encapsulation and PDU names, what happens end to end when you open a website, hub vs switch vs router vs firewall, collision vs broadcast domains, unicast multicast broadcast anycast, bandwidth vs throughput vs latency vs jitter, LAN WAN MAN PAN WLAN, topologies star mesh ring, ARP basics, MAC vs IP addressing roles, client server vs peer to peer, control plane data plane management plane.

2. 02Ethernet and the physical layer 0

   Ethernet frame format preamble MACs EtherType FCS, MAC address structure OUI and unicast multicast bits, copper categories Cat5e Cat6 Cat6A and distances, straight through vs crossover and Auto-MDIX, single-mode vs multimode fiber and distances, connectors LC SC MPO, SFP SFP+ QSFP and transceiver types, speed duplex and autonegotiation, duplex mismatch symptoms late collisions, CSMA/CD and why full duplex removed it, MTU 1500 and jumbo frames, CRC errors runts giants, PoE standards 802.3af at bt and budgets, 10G 25G 40G 100G and lanes, optical power dBm and light levels.

3. 03Switching and VLANs 0

   MAC address table learning flooding aging, store-and-forward vs cut-through, VLANs and why, access vs trunk ports, 802.1Q tag and its fields, native VLAN and its risks, DTP and why to disable it, VTP modes and the revision number disaster, inter-VLAN routing router-on-a-stick vs SVI, EtherChannel LACP vs PAgP vs static and modes, EtherChannel load balancing hash, CDP and LLDP, voice VLAN, private VLANs, switch stacking, layer 3 switch vs router, unknown unicast flooding causes.

4. 04Spanning tree 0

   why STP exists broadcast storms and MAC flapping, BPDU contents, root bridge election bridge ID priority and system ID extension, root port and designated port selection and tie breakers, port costs short vs long, 802.1D port states and timers, RSTP port roles and proposal agreement, PVST+ vs Rapid PVST+ vs MST, MST regions and instances, PortFast, BPDU Guard, BPDU Filter, Root Guard, Loop Guard, UDLD, topology change notifications, root placement aligned with the gateway.

5. 05IPv4 and subnetting 0

   IPv4 header fields, classful addressing and why CIDR replaced it, RFC 1918 private ranges, special addresses loopback APIPA multicast broadcast 0.0.0.0, subnet mask and prefix math, subnetting network broadcast host range, hosts per subnet, VLSM design, route summarization and supernetting, /31 and /32 uses, ARP process and cache, gratuitous ARP, proxy ARP, ICMP types used by ping and traceroute, TTL, fragmentation and the DF bit, CGNAT 100.64.0.0/10.

6. 06IPv6 0

   why IPv6, address format and compression rules, global unicast link-local unique local multicast anycast, no broadcast, EUI-64, SLAAC, DHCPv6 stateful vs stateless, RA M and O flags, NDP NS NA RS RA redirect, DAD, IPv6 header and extension headers, fragmentation in IPv6, solicited-node multicast, dual stack, 6in4 tunnels and NAT64 DNS64, OSPFv3, RA guard and first hop security, privacy addresses, prefix sizes /48 /56 /64.

7. 07Routing fundamentals 45

   routing table and how a router chooses a path, longest prefix match, administrative distance values, metrics, connected and local routes, static default and floating static routes, recursive lookup, ECMP, RIB vs FIB, CEF and the adjacency table, distance vector vs link state vs path vector, route redistribution and loops, route maps, prefix lists vs ACLs, policy-based routing, VRF and VRF-lite, summarization tradeoffs, null0 routes, convergence.

8. 08OSPF 30

   link state and SPF, router ID selection, hello and dead timers, neighbor states Down to Full, what must match to form an adjacency, DR and BDR election and why, network types, LSA types 1 to 7, areas and why area 0, ABR and ASBR, stub totally stubby NSSA, cost and reference bandwidth, summarization at ABR and ASBR, virtual links, authentication, stuck in EXSTART or 2-WAY, passive interfaces, default-information originate, OSPF vs EIGRP vs IS-IS.

9. 09EIGRP, RIP and IS-IS 15

   EIGRP DUAL successor and feasible successor, the feasibility condition, reported vs feasible distance, EIGRP metric and K values, EIGRP packet types and neighbor requirements, stuck in active and stub routers, named mode, unequal cost load balancing with variance, EIGRP summarization, RIPv2 basics and limits, split horizon poison reverse route poisoning, IS-IS levels L1 L2, IS-IS NET addressing, IS-IS vs OSPF at service providers.

10. 10BGP 0

    why BGP and what an AS is, eBGP vs iBGP, neighbor states, TCP 179, iBGP full mesh and its split horizon rule, route reflectors, confederations, next-hop-self, path attributes well-known and optional, best path selection order, weight vs local preference vs AS path vs MED, influencing inbound vs outbound traffic, AS path prepending, communities including well-known ones, multihoming to two ISPs, default routes in BGP, filtering with prefix lists and AS path ACLs, soft reconfiguration and route refresh, timers and BFD, eBGP multihop, private AS numbers, RPKI, hijacks and route leaks.

11. 11Gateway redundancy and high availability 0

    why first hop redundancy, HSRP v1 vs v2 virtual MAC and groups, HSRP states priority and preempt, interface and object tracking with IP SLA, VRRP differences, GLBP AVG and AVF, aligning the active gateway with the STP root, BFD, graceful restart NSF and SSO, stacking vs VSS vs StackWise Virtual, anycast gateway concept.

12. 12DHCP, DNS, NAT and NTP 31

    DHCP DORA and the messages, DHCP relay and ip helper-address, DHCP options 3 6 43 66 150, lease renewal T1 T2, DNS resolution recursive vs iterative, DNS record types A AAAA CNAME MX NS PTR SOA TXT SRV, TTL and caching, DNS over UDP and TCP 53, NAT static dynamic and PAT, inside outside local global, NAT order of operations, port forwarding, NAT and protocols that break, NTP strata and why time matters, file transfer TFTP FTP SCP SFTP.

13. 13TCP, UDP and applications 0

    three way handshake, four way close and TIME_WAIT, TCP header and flags, sequence and acknowledgment numbers, sliding window and window scaling, retransmission and RTO, fast retransmit, congestion control slow start avoidance CUBIC BBR, TCP vs UDP and when to use which, well known ports, MTU MSS and PMTUD black holes, MSS clamping, HTTP 1.1 vs 2 vs 3 and QUIC, TLS 1.3 handshake, certificates and the chain of trust, sockets and ephemeral ports, keepalives, what happens when you type a URL.

14. 14Network security 29

    standard extended and named ACLs, ACL placement, wildcard masks, implicit deny, AAA, RADIUS vs TACACS+, 802.1X EAP supplicant authenticator server, MAB, port security and violation modes, DHCP snooping, dynamic ARP inspection, IP source guard, stateful vs stateless firewalls, zone-based firewall, next generation firewall features, IDS vs IPS, DMZ design, defense in depth, device hardening, control plane policing, attacks MAC flooding VLAN hopping ARP spoofing DHCP starvation DDoS SYN flood, zero trust.

15. 15VPNs and tunnels 0

    site to site vs remote access, GRE and why GRE over IPsec, AH vs ESP, transport vs tunnel mode, IKEv1 phase 1 and phase 2 main vs aggressive mode, IKEv2 differences, security associations and SPI, crypto maps vs VTI, NAT traversal UDP 4500, Diffie Hellman groups, PFS, DMVPN phases 1 2 3 and NHRP, SSL VPN vs IPsec client, WireGuard, a tunnel that is up but passes no traffic, MTU and MSS in tunnels.

16. 16Wireless 45

    802.11 standards and Wi-Fi generations, 2.4 vs 5 vs 6 GHz, non-overlapping channels, channel width tradeoffs, CSMA/CA vs CSMA/CD, SSID BSSID ESS, autonomous vs controller vs cloud managed APs, CAPWAP and split MAC, AP modes, WPA2 vs WPA3 personal vs enterprise, 4 way handshake, roaming 802.11r k v, RSSI SNR and dBm, interference and site surveys, band steering, guest networks and captive portals.

17. 17WAN, MPLS and SD-WAN 0

    WAN options leased line MPLS broadband LTE 5G, PPP and PPPoE basics, Metro Ethernet, MPLS labels and label switching, LDP, PE P CE roles, penultimate hop popping, MPLS L3VPN with VRF RD RT and MP-BGP, MPLS vs internet VPN, SD-WAN overlay controllers and application aware routing, SD-WAN vs DMVPN, hub and spoke vs full mesh WAN, dual WAN failover, latency and SLAs.

18. 18Quality of service 0

    why QoS and when it does nothing, best effort IntServ DiffServ, classification and marking, DSCP CoS and IP precedence, EF AF and CS classes, trust boundary, queuing FIFO WFQ CBWFQ LLQ, policing vs shaping, tail drop vs WRED, voice and video requirements delay jitter loss, MQC class-map policy-map service-policy, QoS over the WAN and the internet, bandwidth vs priority commands.

19. 19Multicast 0

    why multicast vs unicast and broadcast, multicast address ranges 224/4 and SSM 232/8, mapping a group to a MAC address, IGMP v1 v2 v3, IGMP snooping, PIM dense vs sparse mode, rendezvous point and how routers learn it static auto-RP BSR, shared tree vs source tree and SPT switchover, RPF check, SSM, multicast in IPv6 MLD, troubleshooting multicast.

20. 20Data center 0

    three tier vs spine-leaf, east-west traffic, ECMP in the fabric, underlay vs overlay, VXLAN encapsulation VNI VTEP, flood and learn vs BGP EVPN, EVPN route types 2 and 5, anycast gateway, vPC and MLAG, oversubscription ratios, load balancers L4 vs L7 and algorithms, health checks, SNAT on load balancers, storage networking iSCSI FC FCoE, data center interconnect, microsegmentation.

21. 21Monitoring and operations 45

    SNMP v1 v2c v3 and security, MIB and OID, traps vs informs vs polling, syslog and severity levels 0 to 7, NetFlow IPFIX sFlow and what they tell you, streaming telemetry vs SNMP polling, NTP for logs, IP SLA, baselines and thresholds, monitoring tools and dashboards, change management and maintenance windows, backups of configs, MTTR and MTBF, incident response and postmortems, documentation and diagrams.

22. 22Automation and programmability 0

    why automate, SDN planes and controllers, northbound vs southbound APIs, REST methods and status codes, JSON YAML XML, YANG models, NETCONF vs RESTCONF vs gNMI, model driven telemetry, Ansible for network devices and idempotency, Python Netmiko NAPALM, Jinja2 templates, source of truth and NetBox, Git workflows and CI for network changes, Terraform, intent based networking.

23. 23Cloud networking 0

    VPC and VNet basics, public vs private subnets, route tables, internet gateway and NAT gateway, security groups vs network ACLs, VPC peering and why it is not transitive, transit gateway hub and spoke, site to site VPN to the cloud, Direct Connect and ExpressRoute, private endpoints and PrivateLink, cloud load balancers ALB NLB, cloud DNS, IP planning to avoid overlap, egress costs, Kubernetes pods services CNI ingress.

24. 24Linux networking 0

    ip addr ip link ip route, iproute2 vs net-tools, ss and netstat, policy routing ip rule, ip neigh, iptables chains and tables, nftables, conntrack, bridges and VLAN interfaces, bonding modes, network namespaces and veth pairs, tcpdump filters, dig nslookup resolv.conf, curl for debugging, sysctl ip_forward and rp_filter, MTU on Linux, systemd-networkd NetworkManager netplan.

25. 25Troubleshooting 0

    methodology top down bottom up divide and conquer follow the path, OSI layer approach, ping and extended ping, how traceroute works and reading it, first show commands, interface counters CRC input errors drops, SPAN RSPAN ERSPAN and packet capture, reading a TCP stream in Wireshark, slow network vs slow application, intermittent problems, asymmetric routing, MTU problems, DNS problems, duplicate IP, one-way traffic, root cause analysis.

26. 26Network design 0

    hierarchical core distribution access, collapsed core, campus and branch design, redundancy vs complexity, high availability and nines math, single points of failure, IP addressing plan for a company, VLAN and subnet design, choosing a routing protocol, internet edge with two ISPs, scaling as the company grows, capacity planning and oversubscription, a new office of 200 people, migration and cutover planning, behavioral questions about outages and mistakes.