CNEpv flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- OSI Layer 3
- Network layer, responsible for logical addressing and routing of packets between networks using IP addresses and routing tables.
- Subnet usable hosts formula
- Usable hosts equal two raised to the number of host bits minus two, excluding the network and broadcast addresses; a /26 yields 62 usable addresses.
- TCP three-way handshake
- Connection setup sequence of SYN, SYN-ACK, and ACK that synchronizes sequence numbers and confirms both endpoints are reachable before data transfer.
- APIPA address range
- Link-local range 169.254.0.0/16 that a host self-assigns when DHCP is unavailable, allowing local-segment communication only with no default gateway.
- Full mesh topology
- Every node connects directly to every other node, requiring N times N minus one divided by two links, giving maximum redundancy at maximum cost.
- Administrative distance
- Trustworthiness rating of a routing source; lower values are preferred, so a static route (1) beats OSPF (110) for the same destination.
- OSPF cost metric
- Interface cost computed as reference bandwidth divided by interface bandwidth, defaulting to 100 Mbps reference; total path cost sums outbound interface costs.
- EIGRP feasible successor
- A backup route whose reported distance is less than the current feasible distance of the successor, guaranteeing it is loop-free.
- BGP local preference
- Well-known discretionary attribute used inside an autonomous system; the highest local preference is chosen before AS path length comparison.
- STP root bridge election
- The switch with the lowest bridge ID wins, where bridge ID is the priority value followed by the base MAC address.
- 802.1Q trunk tag
- Four-byte tag inserted into Ethernet frames carrying a 12-bit VLAN identifier, marking frames for the correct VLAN across a trunk link.
- HSRP virtual MAC
- Cisco Hot Standby Router Protocol uses virtual MAC 0000.0c07.acXX, where XX is the hex standby group number, shared by active and standby routers.
- ESP versus AH
- IPsec ESP encrypts and authenticates payloads, while AH authenticates only without encryption; ESP is preferred for confidentiality.
- RADIUS versus TACACS+
- RADIUS uses UDP ports 1812 and 1813 and encrypts only the password; TACACS+ uses TCP 49 and encrypts the entire payload with separate AAA functions.
- 802.1X roles
- Port-based access control with three roles: supplicant (client), authenticator (switch or access point), and authentication server (typically RADIUS).
- Dynamic ARP Inspection
- Switch feature that validates ARP packets against the DHCP snooping binding table, dropping forged replies that would enable ARP spoofing attacks.
- Zero trust model
- Security posture that verifies every request explicitly, grants least privilege, and assumes breach rather than trusting traffic based on network location.
- Syslog severity 0
- Emergency level, the most severe syslog value, indicating the system is unusable; levels run from 0 emergency to 7 debug.
- SNMP trap port
- SNMP agents send unsolicited traps and acknowledged informs to the manager on UDP port 162, while polling requests use UDP 161.
- CRC error counter
- Interface statistic counting frames that failed the frame check sequence, usually indicating cabling faults, duplex mismatch, or interference.
- Path MTU discovery
- Technique where a sender relies on ICMP fragmentation-needed messages to learn the smallest MTU along a path and avoid fragmentation.
- REST HTTP status classes
- 2xx indicates success, 3xx redirection, 4xx client-side error such as bad request or unauthorized, and 5xx server-side failure.
- NETCONF transport port
- NETCONF exchanges XML-encoded remote procedure calls over an SSH session on TCP port 830, using YANG-modeled configuration data.
- YANG data model
- Structured modeling language that defines configuration and state data trees for NETCONF and RESTCONF, replacing unstructured CLI parsing.
- Ansible agentless design
- Configuration tool that connects over SSH without installed agents, executing YAML playbooks that declare desired device state idempotently.
- Idempotent automation
- Property where running the same automation repeatedly produces the same end state without making further changes after the first run.
- IaaS responsibility split
- Provider manages physical hosts, network fabric, and virtualization; customer manages operating systems, applications, and their own virtual network configuration.
- VXLAN VNI size
- A 24-bit VXLAN Network Identifier supports roughly 16 million overlay segments, far exceeding the 4094 VLAN limit.
- SDN control plane separation
- Architecture that moves forwarding decisions to a centralized controller, communicating with data-plane devices through southbound APIs such as OpenFlow.
- SD-WAN core function
- Centralized policy and application-aware path selection across multiple WAN transports, typically using encrypted overlays and zero-touch provisioning.
- Type 1 hypervisor
- Bare-metal hypervisor such as ESXi or Hyper-V that runs directly on hardware, offering better performance than hosted Type 2 alternatives.
- SASE convergence
- Framework combining SD-WAN with cloud-delivered security services such as secure web gateway, CASB, and zero trust network access.