Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2 flashcards

A technology that combines multiple network connections in parallel to increase throughput beyond what a single connection could sustain, and to provide redundancy.

• Increases bandwidth and reliability.
• Uses protocols like LACP or PAgP.
• Treats multiple physical links as one logical link.

Memory trick: LACP links, loads of lanes, less downtime.

An open-standard protocol (IEEE 802.3ad) that allows multiple physical Ethernet links to be bundled together to form a single logical channel, providing increased bandwidth and redundancy.

• Also known as EtherChannel (Cisco proprietary) or Port Channel.
• Provides load balancing across aggregated links.
• Ensures high availability; if one link fails, traffic is rerouted over others.

Memory trick: Links Unite for Strength and Safety.

The process of configuring a network device to synchronize its clock with an external NTP server, ensuring accurate timekeeping across the network.

• Uses the `ntp server` command.
• Router acts as a client, polling the server.
• Essential for logging, security, and time-sensitive applications.
• Can specify multiple servers for redundancy.

Memory trick: NTP: How devices keep time in sync.

A networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks.

• Provides highly accurate time synchronization.
• Uses a hierarchical system of stratum levels.
• Supports redundancy with multiple servers for resilience.

Memory trick: NTP's many clocks keep the network's time always right, even if one breaks.

A Layer 3 multicast routing protocol that efficiently routes multicast traffic in networks where receivers are sparsely distributed, using a receiver-driven model.

• Receiver-driven (explicit join).
• Uses a Rendezvous Point (RP) for initial joins.
• Builds shared trees and then switches to shortest-path trees.
• Efficient for sparse environments, conserves bandwidth.

Memory trick: PIM-SM is like a smart TV subscription: only send the channel to those who want it.

A Cisco IP Service Level Agreements (IP SLA) operation that measures performance metrics for UDP traffic, including jitter, latency, and packet loss.

• Sends UDP packets to a specified destination IP address and port.
• Useful for diagnosing real-time application performance issues (e.g., VoIP, video).
• Provides metrics like one-way/two-way delay, jitter, and packet loss.

Memory trick: UDP App Trouble? IP SLA Jitter Will Show the Route.

A wireless network design where access points are centrally managed by one or more wireless LAN controllers (WLCs).

• Offers centralized configuration, monitoring, and troubleshooting.
• Facilitates seamless roaming for clients across multiple APs.
• Provides advanced security features and centralized policy enforcement.

Memory trick: Wireless Architectures: Central Control for Campus Roaming.

An NTP operational mode where two peers actively exchange time information with each other, allowing both to synchronize and potentially serve time.

• Peers actively send and receive NTP packets to each other.
• Provides robust synchronization by allowing both devices to update each other.
• Often used between primary time servers or between a server and a highly critical client that also serves others.

Memory trick: NTP modes define how time flows: one-way, two-way, or peer-to-peer.

A Cisco-proprietary First Hop Redundancy Protocol (FHRP) that provides high network availability by providing a virtual default gateway for IP hosts on a LAN.

• Cisco proprietary.
• Active-standby redundancy model.
• Uses a virtual IP address and virtual MAC address.
• One router is Active, one is Standby, others are Listeners.

Memory trick: FHRPs: Your gateway always stays up.

A communication protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships.

• Operates at the network layer (Layer 3) but is critical for Layer 2 multicast forwarding decisions (e.g., IGMP snooping).
• Allows hosts to 'join' or 'leave' multicast groups.
• Routers use IGMP to determine which multicast groups have interested members on a given subnet.

Memory trick: Multicast Needs: PIM for Routing, IGMP for Joining.

A powerful and flexible feature on Cisco devices that provides the ability to automate tasks and customize event-driven actions.

• Monitors various system-level and network-level events.
• Triggers actions like executing CLI commands, sending emails, or generating SNMP traps.
• Allows for proactive issue resolution and customized automation.

Memory trick: EEM is the router's smart assistant, taking action when events happen.

A Layer 2 security feature on Cisco switches that restricts input to an interface by limiting and identifying MAC addresses of devices allowed to access the port.

• Controls access based on MAC addresses.
• Can be configured with static, dynamic, or sticky MACs.
• Violation modes include shutdown, restrict, protect.

Memory trick: Port Security is the bouncer at the club, only letting approved MACs in.

A powerful, distributed, and customizable event management system integrated into Cisco IOS and IOS XE that allows for automation of tasks based on various events or schedules.

• Automates tasks on the device itself.
• Triggers include syslog, interface status, counters, timer.
• Actions include CLI commands, sending email, Tcl scripts.
• Enhances network resilience and operational efficiency.

Memory trick: EEM is the router's personal assistant, always ready to do tasks on schedule or when something happens.

A Cisco technology that allows network devices to generate and analyze traffic to measure network performance and health proactively.

• Measures metrics like jitter, latency, packet loss, and connection setup times.
• Can be configured for various protocols (e.g., ICMP, UDP, TCP, HTTP).
• Used for network troubleshooting, performance baselining, and verifying QoS policies.

Memory trick: Proactive Performance: IP SLA Tests the Way.

A network protocol developed by Cisco for collecting IP traffic information. It provides statistics on network conversations flowing through a router or switch.

• Collects flow records (source/destination IP, ports, protocol).
• Used for network monitoring, security, billing, capacity planning.
• Requires a NetFlow collector to store and analyze data.

Memory trick: NetFlow is the traffic cop who counts every car and knows where it's going.

A form of Network Address Translation (NAT) that maps multiple internal private IP addresses to a single public IP address by using unique source port numbers.

• Also known as Port Address Translation (PAT).
• Most common type of NAT for Internet access.
• Significantly conserves public IP addresses.

Memory trick: NAT's Many Faces: One-to-One, Pool, or Many-to-One.

A form of network address translation where multiple private IP addresses are mapped to a single public IP address using different port numbers.

• Also known as NAT Overload.
• Allows many-to-one IP address translation.
• Conserves public IPv4 addresses.

Memory trick: PAT lets many private homes share one public post office.

The sequential steps involved in implementing an effective Quality of Service (QoS) policy to manage network traffic.

• Begins with identifying and categorizing different types of traffic.
• Involves marking traffic to indicate its priority level.
• Requires mechanisms to manage and avoid congestion based on these priorities.

Memory trick: VoIP Quality: Classify, Mark, Queue, Drop.

A Cisco feature that allows traffic from source ports or VLANs on one switch to be mirrored to a destination port on a different switch within the same network, using a dedicated RSPAN VLAN.

• Extends SPAN capabilities across multiple switches.
• Requires a dedicated RSPAN VLAN to transport mirrored traffic.
• Destination port must be on a switch participating in the RSPAN VLAN.

Memory trick: SPAN's Mirrors: Local, Remote, or Encapsulated.

Protocols that provide redundant default gateway services for end devices on a LAN, ensuring continuous network access even if a gateway router fails.

• Includes HSRP, VRRP, GLBP.
• Uses a virtual IP and MAC address.
• Transparent failover for end hosts.

Memory trick: FHRP is like having two doormen, if one rests, the other steps right in.

The practice by syslog servers to discard incoming messages if their timestamps fall outside an acceptable time window, often to prevent processing old or invalid data.

• Crucial for data integrity and preventing 'log floods' from misconfigured devices.
• Requires accurate time synchronization (e.g., via NTP) on logging devices.
• Can lead to legitimate log messages being dropped if the source device's clock is severely out of sync.

Memory trick: Old Clock, No Logs: The Server's Trust is Gone.

A table maintained by a network switch that maps MAC addresses to the specific ports on which they were learned.

• Used by switches to forward frames to specific destinations.
• Entries are learned dynamically when a frame arrives from a source MAC address.
• Can be used to identify Layer 2 loops if the same MAC address appears on multiple non-trunk ports.

Memory trick: Look for the Loop with Learned MACs.

A multicast routing protocol used in IP networks where multicast receivers are sparsely distributed and dynamically join/leave multicast groups, building distribution trees only where necessary.

• Designed for sparse receiver environments.
• Uses a Rendezvous Point (RP) to discover sources and receivers.
• Builds shared trees (RPT) and source trees (SPT).
• More scalable than PIM-DM for large networks.

Memory trick: Multicast: Efficiently sending data to many.

A form of Network Address Translation (NAT) that allows multiple devices on a private network to share a single public IP address by using unique source port numbers.

• Also known as NAT Overload.
• Most common NAT type for internet access in homes and small businesses.
• Conserves public IP addresses.

Memory trick: NAT: Many to One? PAT's the Fun!

A Layer 2 feature on Cisco switches that prevents traffic storms by monitoring incoming traffic levels and suppressing excessive broadcast, multicast, or unknown unicast traffic.

• Mitigates broadcast, multicast, and unicast storms.
• Configured per interface.
• Uses thresholds (e.g., percentage or pps) to trigger.

Memory trick: Storm Control stops the flood before it drowns the network.

The process of identifying specific types of network traffic and assigning them a priority level or class.

• Classification identifies traffic based on criteria (e.g., port, protocol, IP address).
• Marking applies a QoS value (e.g., DSCP, CoS) to the packet header.
• Allows downstream devices to apply appropriate QoS policies.

Memory trick: Classify and Mark first, then manage the traffic flow.

A configuration where a switch automatically assigns IP phones to a dedicated VLAN (Voice VLAN) and provides them with the IP address of a TFTP server via DHCP Option 150.

• Separates voice traffic from data traffic for QoS and security.
• DHCP Option 150 is specifically used by Cisco IP phones to find their TFTP server.
• Simplifies IP phone deployment by automating configuration.

Memory trick: Phones Find Home: VLAN, DHCP, TFTP.

A high-performance, distributed Layer 3 IP switching technology used on Cisco devices to accelerate packet forwarding.

• Stores forwarding information (FIB) and adjacency tables in hardware.
• Eliminates the need for per-packet route lookups.
• Crucial for efficient inter-VLAN routing and overall router/switch performance.

Memory trick: CEF is the fast track for packets, bypassing the slow lane.

A First Hop Redundancy Protocol (FHRP) that provides automatic failover for the default gateway, ensuring high availability for end devices.

• Creates a virtual router with a virtual IP and MAC address.
• One router acts as master, others as backups.
• Standardized protocol, alternative to HSRP.

Memory trick: FHRP is like having a backup key for your front door.

The initial steps in a QoS policy where network traffic is identified (classified) based on various criteria and then assigned a QoS label (marked) for preferential treatment.

• Classification identifies traffic using ACLs, NBAR, etc.
• Marking applies DSCP, IP Precedence, or CoS.
• Enables downstream devices to apply QoS policies consistently.

Memory trick: First, you classify the cargo, then you mark it for special handling.

A group of protocols used to provide default gateway redundancy for IP hosts on a shared LAN segment.

• Ensures continuous network access even if the primary gateway fails.
• Protocols include HSRP, VRRP, and GLBP.
• Transparent to end-user devices, which see a single virtual gateway address.

Memory trick: FHRP: Redundancy for Your First Hop.

A QoS queuing mechanism that provides strict priority to delay-sensitive traffic within an output queue, ensuring it is transmitted before other traffic.

• Combines CBWFQ with strict priority queue.
• Ideal for voice and video (real-time applications).
• Minimizes latency and jitter for prioritized traffic.
• Guarantees bandwidth and low delay for critical applications.

Memory trick: Queues: Prioritizing packets for smooth sailing.

QoS mechanisms that deal with traffic when a link becomes congested, typically by using queuing algorithms to prioritize certain types of traffic over others.

• Queuing is a primary component.
• Ensures preferential treatment for critical traffic.
• Examples: LLQ, WFQ, CBWFQ.

Memory trick: Queues keep VoIP clear, like a VIP line at a concert.

A method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device.

• Translates private IP addresses to public IP addresses.
• Enables multiple devices to share a single public IP.
• Crucial for internet access from private networks.
• Provides a layer of security by hiding internal topology.

Memory trick: Internet: How local networks reach the world.

A Cisco IOS feature that provides active monitoring of network performance by generating and analyzing traffic to measure metrics like jitter, latency, and packet loss.

• Generates synthetic traffic (active measurement).
• Measures end-to-end delay, jitter, packet loss.
• Configurable operations (e.g., UDP Jitter, ICMP Echo).
• Can trigger events or track service levels.

Memory trick: IP SLA is the network's personal trainer, actively testing its speed and agility.

A routing strategy where next-hop packet forwarding to a single destination can occur over multiple best paths that have equal cost metric.

• Improves bandwidth utilization and provides redundancy.
• Relies on hashing algorithms to distribute traffic across paths.
• Requires the routing protocol to find multiple paths with identical costs.

Memory trick: Suboptimal Path? Check if ECMP is Missing from the Map.

A Cisco Catalyst switch feature that allows a single access port to carry traffic for both a voice device (VoIP phone) and a data device (PC) by placing them into separate VLANs.

• Uses CDP or LLDP to detect VoIP phones.
• Assigns phone to a dedicated voice VLAN.
• PC traffic remains in the native data VLAN.
• Ensures QoS for voice traffic.

Memory trick: VLANs: Organizing devices for network efficiency.

A Cisco feature that allows traffic from one or more source ports or VLANs to be mirrored to a destination port for analysis.

• Used for network monitoring, intrusion detection, and troubleshooting.
• Non-intrusive; does not affect the forwarding of production traffic.
• Can monitor ingress, egress, or both directions of traffic.

Memory trick: Packet Analysis: SPAN the Traffic for a Deep Scan.

A port-based network access control protocol that restricts unauthorized workstations from connecting to a LAN through publicly accessible switch ports.

• Uses a supplicant (client), authenticator (switch), and authentication server (e.g., RADIUS).
• Requires devices to authenticate before gaining network access.
• Can use various authentication methods like EAP (Extensible Authentication Protocol).

Memory trick: Access Control: Authenticate Everything at the Door.

A Cisco proprietary First Hop Redundancy Protocol (FHRP) that provides high network availability by providing a default gateway IP address that is always available.

• One router is Active, forwarding traffic.
• Another router is Standby, monitoring the Active router.
• Uses a virtual IP and MAC address for the default gateway.

Memory trick: FHRP: Your Gateway's Backup Plan.

A feature that allows network traffic to be monitored across multiple switches by mirroring traffic to a destination port on a different switch.

• Uses a dedicated RSPAN VLAN to carry mirrored traffic between switches.
• Requires configuration on both source and destination switches.
• Provides full packet capture for analysis but limited to Layer 2 domains.

Memory trick: SPAN is the mirror, RSPAN is the mirror across the room, ERSPAN is the mirror across the globe.

A Cisco technology that actively monitors network performance by generating and analyzing synthetic traffic to measure metrics such as latency, jitter, packet loss, and connectivity.

• Performs active, synthetic measurements.
• Can simulate various application traffic types (e.g., ICMP echo, UDP jitter, HTTP).
• Used for proactive monitoring, troubleshooting, and verifying QoS policies.

Memory trick: Performance: Measure, Simulate, Alert.

An STP enhancement that prevents alternate or root ports from transitioning to a forwarding state if they stop receiving BPDUs, thereby protecting against Layer 2 loops.

• Prevents blocking ports from becoming forwarding.
• Monitors BPDU reception on non-designated ports.
• Protects against unidirectional link failures or software errors.
• Enhances STP stability and loop prevention.

Memory trick: Loop Guard: Guards against rogue forwarding where BPDUs disappear.

A Cisco feature that allows mirroring traffic from source ports/VLANs on a switch and sending it to a destination port on a different switch or analyzer across a Layer 3 network by encapsulating the mirrored traffic in a GRE tunnel.

• Supports monitoring across Layer 3 boundaries.
• Encapsulates mirrored traffic using GRE.
• Requires source and destination ERSPAN sessions.

Memory trick: ERSPAN: Encapsulate Remotely, Span Everywhere

A logical interface on a multilayer switch associated with a VLAN, providing Layer 3 routing capabilities for that VLAN and serving as its default gateway.

• Enables inter-VLAN routing on a multilayer switch.
• Must be configured for each VLAN that requires Layer 3 routing.
• Acts as the default gateway for devices in its associated VLAN.

Memory trick: SVI: S for Switch, V for Virtual, I for Interface - the virtual router for VLANs.

A Cisco proprietary protocol that monitors the physical integrity of a link to detect if traffic is flowing in only one direction, which can prevent Layer 2 issues.

• Detects unidirectional links.
• Operates at Layer 1/2.
• Can disable a port upon detection.
• Prevents issues like loops and traffic blackholes.

Memory trick: UDLD: Unidirectional Link Detector, sees if the road is one-way when it should be two.

PIM Sparse Mode (PIM-SM) is a multicast routing protocol optimized for environments with sparsely distributed receivers. It builds explicit shortest-path trees from a Rendezvous Point (RP) to active receivers, avoiding unnecessary traffic flooding.

• Explicit join model.
• Uses a Rendezvous Point (RP).
• Minimizes unnecessary traffic flooding.
• Suited for sparsely distributed receivers.

Memory trick: Sparse receivers? PIM-SM's the choice, to deliver streams with a quiet voice.

DHCP Snooping is a Layer 2 security feature that filters untrusted DHCP messages and builds a binding database to prevent rogue DHCP servers and enhance network security.

• Prevents rogue DHCP servers.
• Builds a DHCP snooping binding table.
• Classifies ports as trusted or untrusted.
• Used by IP Source Guard and Dynamic ARP Inspection.

Memory trick: Snoop out the rogue, Guard the source, Inspect the ARP, Secure the port.

UniDirectional Link Detection (UDLD) is a Cisco proprietary Layer 2 protocol that monitors the physical integrity of a link to ensure bidirectional communication, detecting and disabling unidirectional links that can disrupt network protocols.

• Cisco proprietary.
• Detects unidirectional links.
• Prevents STP issues (loops, black holes).
• Operates in normal or aggressive mode.

Memory trick: UDLD sees if flow goes both ways, preventing silent network disarray.

A controller-based wireless architecture uses a centralized Wireless LAN Controller (WLC) to manage and configure multiple lightweight Access Points (APs), providing centralized control, seamless roaming, and consistent policy enforcement.

• Centralized management via WLC.
• Seamless roaming for clients.
• Consistent security and QoS policies.
• Scalable for large deployments.

Memory trick: For control and roam, the controller makes the home.

IP Service Level Agreements (IP SLA) is a Cisco feature that generates and analyzes traffic to measure network performance metrics like jitter, latency, packet loss, and more, for proactive monitoring and troubleshooting.

• Generates synthetic traffic.
• Measures end-to-end performance metrics.
• Supports various operation types (UDP Jitter, ICMP Echo).
• Used for baselining, QoS verification, and troubleshooting.

Memory trick: To know the 'SLA' of your 'IP' path, generate traffic and measure its wrath.

A Network Time Protocol (NTP) mode where a device (client) requests time from an NTP server and adjusts its own clock based on the server's responses, without acting as a time source for other devices.

• Most common mode for end devices to synchronize time.
• Unidirectional time synchronization (client pulls from server).
• Simple to configure and provides accurate time.

Memory trick: Clients Connect, Servers Serve Time

A DHCP option specifically used by Cisco IP phones to obtain the IP address of the TFTP server from which they download configuration files and firmware.

• Crucial for Cisco IP phone registration.
• Points to the Cisco Unified Communications Manager (CUCM) or a dedicated TFTP server.
• Ensures phones receive necessary configuration for operation.

Memory trick: 150 for TFTP Phone Setup

FlexLink is a Cisco proprietary Layer 2 feature that allows configuration of a primary and a backup interface pair, enabling rapid failover (sub-second) when the primary link goes down, bypassing Spanning Tree Protocol convergence.

• Cisco proprietary.
• Primary/backup interface pair.
• Sub-second failover.
• Bypasses STP convergence time.

Memory trick: Flex your links for a fast switch, no STP delay, no hitch.

ERSPAN (Encapsulated Remote SPAN) is a Cisco feature that allows monitoring of traffic from source ports/VLANs and encapsulates it into a GRE tunnel for forwarding across Layer 3 networks to a remote destination for analysis.

• Mirrors traffic from source to destination.
• Encapsulates traffic in GRE.
• Transports across Layer 3 boundaries.
• Ideal for remote monitoring by IDS/analyzers.

Memory trick: ERSPAN's the tunnel, L3's the way, for IDS to see traffic far away.

Per-VLAN Spanning Tree Plus (PVST+) is a Cisco proprietary enhancement to STP that runs a separate Spanning Tree instance for each VLAN, allowing for independent root bridges and load balancing across redundant links.

• Cisco proprietary.
• Runs an STP instance per VLAN.
• Allows load balancing per VLAN.
• Prevents Layer 2 loops.

Memory trick: For each VLAN, a PVST+ path, preventing loops and Wrath.

A core component in Cisco SD-Access responsible for maintaining the host database (EID-to-RLOC mapping) using LISP, enabling host mobility and IP address persistence within the fabric.

• Based on LISP Map-Server/Map-Resolver functionality.
• Stores information about where endpoints are connected.
• Facilitates seamless roaming and IP address retention for endpoints.

Memory trick: Control Plane 'knows' where everyone is, Border 'guards' the edge.

A wireless network architecture where access points (APs) are managed and controlled by a central wireless LAN controller (WLC).

• Centralized management and configuration.
• Advanced RF management and optimization.
• Seamless roaming and QoS enforcement.

Memory trick: Autonomous APs are 'lone wolves', controllers are the 'pack leaders'.

A feature of Cisco SD-Access that enables granular security segmentation within the campus network, applying policies based on user identity and device posture, independent of network topology.

• Uses Virtual Networks (VNs) for macro-segmentation.
• Uses Scalable Group Tags (SGTs) for micro-segmentation.
• Enables dynamic policy enforcement and limits blast radius.

Memory trick: SD-Access tags users, firewall guards doors, VLANs draw lines.

A network virtualization technology that creates multiple independent routing and forwarding tables within a single router or switch, enabling complete Layer 3 isolation.

• Each VRF acts as a separate virtual router.
• Provides complete isolation of routing tables and forwarding instances.
• Allows overlapping IP addresses between different VRFs.

Memory trick: VLANs divide LAN, VRFs divide Routers.