CCNP: ENCOR Exam 350-401

Understand how virtual LANs create smaller broadcast domains, grouping devices across switches and buildings, and use inter-VLAN routing to connect subnets mapped to IP networks.

Create a vlan by assigning a unique vlan id and optional name, note the 1000-1001 range with reserved blocks, and always use the vlan after creation.

Assign a port to a VLAN to place devices on the right network; use a single port for both a computer’s access VLAN and a phone’s voice VLAN, reducing cabling.

Create a VLAN, view its name and active status, and use commands to display specific VLAN information.

Create a VLAN (cont.) with a concise, quick overview in a shorter format for the CCNP: ENCOR exam 350-401.

Explore basic vlan concepts by inspecting interface details with the show interface command and viewing layer 2 settings, including access mode and voice vlan 20, using the switchboard view.

Discover how 802.1Q trunking efficiently carries multiple VLANs over a single link between switches, replacing the brute force approach of wiring separate VLAN cables.

Explore 802.1Q trunking that carries multiple VLANs over a single link by tagging frames with their VLAN and stripping the tag at the destination.

Explore VLAN tagging on trunks, where frames are encapsulated with a VLAN id, and understand how default VLAN 1 and native VLAN affect untagged traffic and security options.

Explain IEEE 802.1Q VLAN tagging, showing how a VLAN header with type 0x8100, priority, MAC address encoding flag, and the VLAN ID is added to frames, altering the frame checksum.

Learn how the native vlan handles untagged ethernet frames across a link, typically vlan 1, and how security settings may change it, with an incredibly easy configuration.

Configure an 802.1q trunk by setting the switchport mode trunk and optionally changing the native vlan to illustrate how the native vlan can be modified.

Configure and verify an 802.1q trunk on the switch interface, run the verification command, and confirm trunk mode is operating.

Configure an 802.1Q trunk, review trunk features, ensure trunking is on, and maintain the native vlan 99 or leave it unchanged when undefined, enabling multiple vlans over a single cable.

Learn how inter-VLAN routing enables communication between separate VLAN broadcast domains by routing traffic through a layer 3 device, assigning each VLAN a unique subnet, and making routing decisions.

The lecture compares using a separate interface for each VLAN with the router on a stick approach, showing how router on a stick simplifies handling multiple VLANs.

Compare router on a stick with a single trunk interface to layer 3 switches that perform inter-VLAN routing, highlighting scalability and routing capabilities across VLAN 10 and VLAN 20.

Demonstrates troubleshooting trunking issues and VLAN issues. Diagnose native VLAN mismatches and adjust allowed VLANs with show interfaces trunk.

Explore layer 2 switch operation, using MAC addresses and the CAM table to forward frames, flood unknown destinations within the VLAN, and handle broadcast, unknown unicast, and multicast frames.

Explain how a layer 2 switch processes inbound frames by consulting mac address table, floods when unknown, uses ternary content addressable memory for wildcard lookups, and applies quality of service.

Explain how the mac address table (cam table) guides layer 2 forwarding on Catalyst switches, and how tcam speeds processing with inbound/outbound access lists and wild card lookups.

Explore how a switch builds and inspects its CAM table, view learned MAC addresses, filter by interfaces, and adjust aging from 300 to 600 seconds.

Describe how the control plane learns routing information to build a routing table, then populates a forwarding table in the data plane to forward packets.

Process switching uses the CPU to handle every packet with layer 2 and layer 3 lookups, frame rebuild, and CRC, like a traditional bridge, making it the slowest switching method.

Explain fast switching: the first packet undergoes CPU processing, then hardware caching enables subsequent frames to be rewritten with addresses via a single lookup.

Compare switching mechanisms, focusing on sayef as the default, fastest hardware-based forwarding using a forwarding information base, which is faster than fast switching or process switching, with some compatibility limits.

Explore how process switching and fast switching decide packet handling, check the fast switch cache, process the first frame, and populate the cache for subsequent fast switching.

Explore Cisco Express Forwarding, a hardware-accelerated data plane that speeds routing via a forwarding information base and adjacency data, with exceptions handled in software.

Analyze Cisco express forwarding by examining the forwarding and adjacency tables with show ip cef and show adjacency, then enable or disable routing components to observe changes.

Aggregate multiple high-speed links into one logical connection to balance load, gain redundancy, and boost bandwidth, usable on routers, servers, switches, and clients.

EtherChannel aggregates multiple links for load sharing and high bandwidth, presenting as a single logical link to spanning tree and providing redundancy and failover.

EtherChannel bundles multiple physical ports into a single logical link between two switches, with ports of the same type (up to 16), and spanning-tree prevents loops.

Explore etherchannel modes: lacp, pagp, and static, including lacp negotiation across vendors, up to 16 links with 8 active, pagp desirable and auto modes, and static requires manual configuration.

Identify ports on each switch, configure etherchannel channel group, set the mode, and choose the protocol (PAgP or LACP) with auto or desirable and active or passive for basic configuration.

Identify port-channel interfaces and ensure identical speed, duplex, and model, with the same vlan on a trunk. Configure at the port-channel level to apply changes to all links and prevent mismatches.

Explore EtherChannel load-balancing options by using destination IP or destination MAC, and consider source IP or source MAC with port-based balancing for diverse traffic paths.

Examine how etherchannel load balancing uses a simple xor hash to select links, enabling third-channel load balancing and balancing traffic across two, four, eight, or sixteen links.

Identify and fix etherchannel issues by spotting and correcting configuration mismatches across both sides, whether in layer 2 or layer 3, so the link comes up.

Diagnose EtherChannel by checking physical connectivity and channel settings, verify manual versus aggregation protocol, and ensure both sides match active-active or desirable-desirable configurations.

Troubleshoot etherchannel by selecting a suitable load balancing algorithm, ensuring traffic uses multiple paths rather than a single gateway, and tailoring the policy to source ip, destination ip, or both.

Troubleshoot layer 2 port aggregation by reviewing the etherchannel summary and lacp status, configure lacp on both switches, and align trunk settings to bring the port channel up.

Examine EIGRP features, including classless routing with variable length subnet masking, fast convergence with backup routes, partial and bounded updates, and equal-cost load balancing across IP and IPv6 paths.

Explore how EIGRP uses RTP, the reliable transport protocol, not tcp or udp, to deliver messages with sequence numbers for multicast, including acknowledgments and a trailer for validation.

Explore how EIGRP forms neighbor relationships with hello packets, exchanges updates, and selects a successor and a feasible successor as backup routes.

Eigrp packet format uses hello, update, query, reply, and acknowledgement within a reliable transport protocol to enable conversational neighbor discovery, route updates, and on-demand information requests during link failures.

Establishes EIGRP neighbor adjacency by agreeing on the autonomous system number and K values for metrics. Sets the required subnet and optional authentication, using passive interfaces to suppress hellos.

Explore how EIGRP metrics use the lowest bandwidth across hops, sum delay, and ignore load and reliability; K-values shape the metric, with MTA in advertisements, not calculations.

Explain the classic EIGRP metric calculation using bandwidth and delay, where bandwidth is scaled by min bandwidth and the metric equals bandwidth plus delay times 256.

Enable wide metrics in EIGRP to support higher bandwidth links, from 100G to 400G and beyond, addressing limitations of the old metric.

Populate the neighbor table from directly connected routers and adjacencies for IPv4 and IPv6. Compute the feasible distance by adding the advertised distance to the cost to reach the neighbor.

Analyze how a diffusing update, driven by a finite state machine, uses feasible distances to select the successor and feasible successor as a loop-free routing backup.

Explore how EIGRP load balancing goes beyond equal-cost paths by enabling unequal-cost load balancing, letting a percent of traffic go over one path and the rest over the other.

Explain unequal cost load balancing and examine how equal costs yield the same outcome in balancing network traffic.

Enable unequal cost load balancing by applying a variance factor to include routes within a cost range multiplied by that factor, with default one for equal-cost routing, and leverage traffic sharing intelligence.

Explore traffic sharing and router load balancing by distributing traffic across links based on metric ratios, applying commands that configure the minimum-cost path routing even with multiple paths.

Examine how path costs and a variance factor drive traffic sharing and load balancing to maximize network throughput, illustrated by costs like 40+50=90, 80, and 105.

Explore the easy design of EIGRP for IPv6, showing how it operates like the familiar protocol while keeping databases separate and running another instance for the protocol.

Explore EIGRP components by establishing neighbor relationships, applying the dual algorithm to determine the best path, and enabling equal-cost and unequal-cost load balancing across IPv4 and IPv6.

Compare eigrp and ospf routing protocols, noting eigrp's quick convergence and easy setup, against ospf's suitability for medium to large networks and open-standard multi-vendor support, with IPv6 in both.

Demonstrates configuring EIGRP stub routing, verifying queries, and using route summarization and default routing with static redistribution to control routing behavior.

Configure EIGRP load balancing with unequal-cost routing using variance, then implement IP authentication on the link with MD5, using key chains on both green and red routers.

Explore inter-domain routing with BGP between autonomous systems, contrasted with interior gateway protocols inside an autonomous system, highlighting exterior gateway protocols as a key characteristic.

BGP prioritizes reliability and stability with keepalive messages and incremental updates, avoiding full-table advertisements. It handles many routes via a TCP sliding window, favoring slower, stable convergence.

Explore how BGP uses path vector to advertise a path through autonomous systems, enabling loop-free destinations. Understand how an autonomous system path preserves loop-free routing and guides reachability across networks.

Explore how BGP routing policies empower autonomous systems to control path selection and traffic handling with fine-grained control and scalable internet routing.

Establish BGP neighbors with TCP 179, exchange routes, and populate forwarding and IP routing tables; advertise the best routes to peers for equal-cost load balancing.

BGP establishes a neighbor relationship after a TCP connect by an open message with version, autonomous system, and router IDs, then exchanges keepalives and updates to manage reachability.

Understand how two BGP speakers form peer relationships with neighbors, distinguishing internal neighbors within the same autonomous system from ebgp across different autonomous systems.

Explore how eBGP neighbor relationships establish peering between routers in different autonomous systems, using exact neighbor IP addresses and TCP port 179 to exchange reachability information and route data.

In BGP path selection, evaluate multiple exits in a multi-homed deployment to determine the best path using diverse policies and criteria beyond simple metrics.

Explore the BGP best path selection algorithm, balancing weight and local preference while comparing origin, MED, and AS-path attributes to choose the best route across two ISP connections.

Explore how BGP path attributes shape routing decisions by distinguishing well-known attributes, optional well-known, and mandatory versus discretionary attributes used in path selection.

Learn how BGP path attributes shape routing decisions, including origin, AS path, next hop, local preference, atomic aggregate, and the roles of mandatory, discretionary, transitive, and non-transitive attributes.

Explore the weight attribute in Cisco tools to influence path selection by assigning weights, such as preferring a 300 path with weight 200 over a 200 path with weight 100.

Learn how weight and local preference influence route choice across multiple paths. Local preference is an autonomous system wide metric updated across the network.

The as-path attribute is a sequence of autonomous system numbers that shows how to reach a destination, and it prevents loops by not re-adding its own number.

Master the med attribute and its role in shaping inbound traffic by advertising preferred paths with discriminators. Learn how lower med values influence path selection within vpe path attributes.

Configure eBGP between two routers, using neighbor and network commands to advertise networks. Verify neighbors with show ip bgp summary and show ip bgp neighbors, then test connectivity with ping.

Describe how ospf, a link-state interior gateway protocol, models interfaces with ip addresses, uses lsa to share link state with neighbors, and builds a topological map via spf.

Describe OSPF components by explaining the autonomous system, backbone area zero, and other areas, and how areas group devices within an administration and connect to external networks.

On a router, OSPF runs as a single, locally significant process identified by a process id. You can choose any value, and this keeps OSPF processes isolated from each other.

Configure a single device to run two separate OSPF processes, each connecting to a different OSPF network, and share routes by redistributing between them.

Understand how the OSPF process selects the router ID: manual config, then the highest loopback IP, then the highest active physical IP, and how loopback IDs appear in link-state advertisements.

Explore configuring the ospf process across routers, choosing and verifying a correct process id (255) and setting interface priority, with alternative approaches discussed.

Use the lookback interface to avoid router ID changes, allow the OSPF process to figure out its router ID, and start participating in state advertisements to prepare to discover neighbors.

discover how ospf neighbor adjacencies form by exchanging hello packets with multicast addresses 224.0.0.5 and 224.0.0.6, and why both sides must agree on area id, authentication, and hello/dead intervals.

Learn how OSPF neighbor adjacencies form by exchanging hello information, detect mismatches that prevent neighbors from forming, and proceed to build the link-state database once neighbors are established.

Explore how routers exchange database descriptions to build a link-state database and establish neighbor relationships. Use link-state requests, updates, and acknowledgments to synchronize topology information.

Explore the five basic OSPF packet types, including type 1 and type 2 (databases), type 3 for data propagation, and type 5 (acknowledgement), with emphasis on flooding.

Explore the OSPF packet header format, including version, type, router ID, and authentication. See how the data breaks into LSA types that feed the link-state database.

Explore the main OSPF LSA types, including network LSA and summary LSA, and learn how LSA 3 and LSA 5 support larger environments with autonomous system boundary routers.

Discover how OSPF uses type 1 and type 2 LSAs, with type 3 summaries and type 5 ASBA advertisements to manage external routes inside an area.

Compare single-area and multi-area OSPF, showing how small networks stay simple, while larger ones use area border routers and backbone area 0 to summarize routes and confine advertisements.

Explore the differences between single-area and multi-area OSPF, including backbone area 0, areas 1 and 2, autonomous system border routers, and how external routes are advertised with the E designation.

Explore ospf area structure, focusing on backbone area (area 0) that all areas connect to. Understand how routes transit via area 0 and how Dijkstra's algorithm finds best path.

Design your OSPF structure by selecting area border routers and an autonomous system boundary router, connect area zero to other areas, plan the SPF design, and configure virtual links.

Explore OSPF network types, including point-to-point, point-to-multipoint, and broadcast or NBMA segments, and how designated router and backup designated router elections occur, with loopback aiding router IDs.

Demonstrates migrating from legacy OSPF to OSPFv3 using the newer syntax for IPv4 and IPv6. Verifies configuration through show commands, sets passive interfaces, and confirms neighbors and routing tables.

Compute the ospf cost by dividing the reference bandwidth by the interface bandwidth, yielding a numeric cost where lower values indicate better routes.

The lesson explains how OSPF uses the shortest path first algorithm to compute topology costs and select the least-cost path from a router to a destination.

Explore how ospf cost is calculated from learned link states and the link-state database, using dijkstra's algorithm to select the path, and adjust cost via manual settings or bandwidth command.

Design OSPF areas intelligently in networks to minimize inter-area advertising, using the area range command to summarize address ranges and the summary address command on the ABR for external routes.

Route summarization enhances network stability by consolidating many routes into a single summary (type three LSA), reducing advertisements between areas and containing changes, with filtering available later.

Apply a distribute list to filter traffic using a standard access list, denying specific source addresses, inbound or outbound, while noting performance considerations.

Explore how a prefix list enables high-performance filtering by translating prefixes into a tree structure that rapidly tests sequence numbers to permit or deny traffic.

Explore route maps to gain advanced control with named maps, a top-down process, and flexible match and set criteria beyond prefix lists and access lists.

Master route map applications to exercise powerful control, enabling policy-based routing in BGP and flexible use for redistribution and other routing tasks.

Explore how route map operations combine match and set statements with sequence numbers to permit or deny routes in BGP contexts.

Explore how route match statements in a brand map evaluate multiple criteria in a top-down order, where the first match applies and sets metrics and interface actions.

Configure route maps by matching criteria and setting metrics to implement policy-based routing, controlling route sharing and redistribution based on source and destination criteria.

Explore how OSPF stub and totally stubby areas reduce routing table size by using default routes and the default-information originate command, with IPv4 and IPv6 configurations.

Explore how private addresses translate to public addresses using overload as port address translation, enabling multiple hosts to share a single external address while highlighting security benefits and traceability trade-offs.

Cisco defines nat address types such as inside local, inside global, outside local, and outside global, explaining how location and translation affect address visibility.

Explore NAT implementations: static one-to-one mappings, dynamic NAT with address pools, many-to-many, and PAT, enabling multiple devices to share a single public IP.

Understand static NAT as a one-to-one translation between internal and public addresses, translating inbound and outbound traffic, and exposing whole IPs or specific ports for public services.

Explore dynamic nat, mapping many inside addresses to outside addresses with automatic reciprocal entries, enabling return traffic, and note its limited use.

Explore port address translation, the most common form of NAT. Learn how the NAT table maps source IP and port to a global address and how replies match conversations.

Learn how the NAT virtual interface (NVI) removes the need to identify inside and outside interfaces, and see a step-by-step config example of using a virtual interface.

Explain NAT virtual interface by using access-list 10 to match 192.168.1.x sources and translating them to the address on interface fastethernet0/1, enabling flexible source-to-interface translation.

Configure static network address translation on the router, mapping inside local to inside global, and verify translations with show ip nat translations and ping tests.

Explore how to implement first-hop redundancy for default gateways to maintain traffic when a gateway or link fails, and understand why redundant gear alone isn’t enough.

Define fhrp and explain how a primary gateway handles traffic with a standby router taking over on failure, using hrp, brp, and glbp for redundancy and load balancing.

Configure FHRP to create a virtual router with a shared default gateway IP address. Switch traffic to the backup router when the primary fails, keeping the same gateway for hosts.

Explore how HSRP interface tracking lets multiple devices share a single default gateway and automatically fail over when the upstream interface to the destination is down.

Configure hsrp interface tracking to adjust priority when a link fails, using the preamp command to determine active and standby roles.

Configure HSRP interface tracking, learn about group designation (including group zero), assign interface types and numbers, and set interface priorities (default 10) for multi-interface scenarios.

Learn to implement hsrp multigroup for load sharing across vlan 10 and vlan 20, with spanning-tree roots guiding vlan 10 to the top switch and vlan 28 to the bottom.

Explore a multigroup HSRP configuration with primary and secondary gateways for subnets 10.1 and 20.1, using priorities 110 and 90 for load sharing on device one.

Configure two devices to share load with HSRP multigroup, assigning one as primary for one gateway and the other as primary for the second gateway across VLANs.

Implement modified authentication in hsrp to verify device identities and prevent rogue devices from joining the group.

Explore HSRP versions, with version two dominating modern environments, offering IPv6 support and group numbers up to 4095, and note that omitting a version defaults to version one.

Explore Cisco switch high availability by examining redundant supervisors and modes such as R, R plus, and SSL, contrasting failover times from partial to boot with stateful set and SSO.

Enable Cisco nonstop forwarding with stateful switchover on Catalyst 9400 to rapidly rebuild the forwarding information base after failover, achieving about 150 ms switchover and under 200 ms traffic interruption.

Configure HSRP to enable quick failover between routers by setting standby groups, a virtual IP, and preemption, then verify with show standby and timer adjustments.

Explore configuring VRRP to establish a virtual router redundancy group, assign virtual IPs, set interface priorities to elect a master, and verify with show commands.

Explore how the spanning-tree protocol prevents broadcast storms and mac address table instability by blocking ports and placing ports in standby to stop loops.

Explore how spanning-tree protocol elects a root bridge by MAC address, assigns root and designated ports, and blocks non-designated ports to prevent loops.

Explore the bridge protocol data unit (BPDU) used by the spanning tree protocol, including message types, topology change notifications (TCN), and fields like root bridge, cost, and flags.

Explain how BPDU and TCN propagate topology changes, with topology change acknowledgments and root-driven configuration BPDUs updating bridges during a triggered network event.

Explain how the root bridge is elected by the lowest bridge ID, formed from bridge priority and MAC address. Adjust the priority in 4096 increments to influence the election.

Discover how a root bridge election uses the lowest cost and port ID tie-breakers to select the best port, and how equal-cost paths, including port channel behavior, are resolved.

Identify the designated port on each segment by choosing the lowest cost; in ties, use the lowest center bridge and then the lowest port ID as tie-breakers.

Explore the STP port states, from admin down and shut down to blocking, listening, learning, and forwarding, and observe how links transition through these states as they come up.

Explore spanning tree protocol types and features, from the original STP to PVST+ with per-VLAN instances, and rapid spanning tree variants for faster convergence across VLANs.

Compare stp protocols and decide when to use mstp versus rsvp, noting mstp provides multiple instances while often offering a single, more efficient instance in a Cisco environment.

Identify the default spanning-tree configuration, PVST+ as the default, its trade-offs, and how VLANs can be split 50/50 across two paths for load balancing.

Group traffic destinations to reduce simultaneous MCP instances, route data center traffic and internet traffic separately, and preserve backward compatibility while ensuring all links are utilized.

Explore multiple spanning tree protocol recommended practices to optimize trunk port behavior and automatic failover, moving beyond manual configurations to determine what traffic is allowed across trunks during failures.

Assign VLANs to separate mst instances and set per-tree link preferences to balance traffic and provide redundancy, preventing dead links.

Configure and verify multiple spanning tree protocol (MST) across switches, create instances, and assign root and secondary roles. Use show commands and port priorities to validate MST.

PortFast and BPDU Guard affect how switch ports move through blocking, listening, and learning states, with total startup delays around 50 seconds, impacting user connectivity when plugging in a laptop.

PortFast brings the link up quickly on access ports connected to PCs, bypassing listening states. BPDU Guard prevents misconfiguration by shutting down an access port if a switch is detected.

Configure PortFast and BPDU Guard by choosing per-port settings or applying defaults to all ports to simplify port protection configurations.

Enable PortFast and BPDU Guard on four access ports connecting servers and endpoints, then verify by inspecting the interface which shows it is enabled.

Verify PortFast and BPDU Guard on the interface, recognizing PortFast as a useful protocol for us.

Explore different ways to verify that PortFast and BPDU Guard are enabled for me when I take a look.

Explore the commands to enable and verify PortFast and BPDU Guard, and learn how to confirm correct configuration and protective behavior in the network.