Nokia NRS II flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Administrative distance

Trust ranking used to choose among routes to the same prefix learned from different sources. Lower values win; connected is most trusted, then static, eBGP, OSPF, IS-IS, iBGP.

OSPF area 0

The backbone area every other OSPF area must connect to. Inter-area routes pass through it, and all ABRs must maintain at least one interface in area 0.

IS-IS Level 1

Intra-area routing level. Level 1 routers share a single area's link-state database; L1/L2 routers advertise an attached bit so L1 routers forward external traffic toward Level 2.

BGP local preference

Well-known discretionary attribute propagated within an autonomous system. Highest value wins during best-path selection and is the primary tool for outbound traffic engineering.

BGP route reflector

Router allowed to reflect iBGP routes to other iBGP clients, removing the full-mesh requirement. Clients treat reflected routes as learned from the reflector; originator ID prevents loops.

BFD

Bidirectional Forwarding Detection: lightweight hello protocol giving sub-second link or path failure detection independent of routing protocol timers. Timers and multiplier must match on both peers.

Next-hop-self

iBGP command causing a router to advertise its own address as next hop for reflected or eBGP-learned routes, so peers can resolve the next hop through the IGP.

Route recursion

Process of resolving a route's next hop through another, more specific route in the routing table. If resolution fails, the route stays inactive and is not installed.

IPv4 private ranges

RFC 1918 address space not routed on the internet: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. They require NAT or tunneling to reach public destinations.

IPv6 link-local address

Address in fe80::/10 automatically configured on every IPv6 interface, used for NDP and next-hop resolution. It is never forwarded beyond the local link.

Neighbor Discovery Protocol

ICMPv6-based mechanism replacing ARP. It handles address resolution, duplicate address detection, router discovery and stateless address autoconfiguration using RS, RA, NS and NA messages.

Path MTU Discovery

Technique where a source learns the smallest MTU along a path from ICMPv4 Fragmentation Needed or ICMPv6 Packet Too Big messages, then sizes packets to avoid fragmentation.

802.1Q tag

Four-byte VLAN tag inserted in the Ethernet header carrying a 12-bit VLAN ID and priority bits. It reduces the payload budget available under a fixed interface MTU.

DHCP DORA

Four-message exchange: Discover, Offer, Request, Acknowledge. Relay agents insert the gateway address so the server can pick the correct address pool.

Subnet host formula

For a prefix with h host bits, usable addresses equal 2^h minus 2 for classic subnets. Point-to-point links may use /31 with two usable addresses under RFC 3021.

RSTP port states

Rapid Spanning Tree uses three states: discarding, learning and forwarding. Port roles are root, designated, alternate and backup, converging far faster than classic STP.

Root bridge election

Lowest bridge ID wins, where the ID combines configurable priority in 4096 steps with the switch MAC address. The root bridge has all ports designated.

LACP active mode

Link Aggregation Control Protocol mode where the port actively sends LACPDUs to negotiate a bundle. It interoperates with passive mode; all member links must match in speed and VLANs.

MC-LAG

Multi-chassis LAG: two aggregation switches coordinate to present a single logical LAG to an access device, providing redundancy without spanning-tree blocking.

Native VLAN mismatch

Condition where the untagged VLAN differs on the two ends of an 802.1Q trunk. Untagged frames then land in different broadcast domains, causing leaks and connectivity faults.

BPDU guard

Feature on edge or portfast ports that err-disables the port if a BPDU is received, preventing an unauthorized switch from joining and altering the spanning tree.

MAC address aging

Timer, typically 300 seconds, after which an unused dynamically learned MAC entry is removed from the forwarding table. Traffic to it is then flooded until relearned.

NETCONF transport

Protocol using SSH on TCP port 830 to exchange XML-encoded RPCs. It supports candidate datastores, locking, validation and confirmed commits against YANG-modelled devices.

YANG datastores

Data trees holding device configuration and state. Running is active, candidate holds uncommitted edits, startup persists across reload, and operational state is read-only.

gNMI

Model-driven interface over HTTP/2 using protobuf. It provides Get, Set, Subscribe for streaming telemetry and Capabilities, commonly paired with YANG models.

RESTCONF verbs

HTTP mapping of YANG data: GET reads, POST creates, PUT replaces, PATCH merges and DELETE removes. Payloads are JSON or XML and paths follow the YANG tree.

Idempotent automation

Property where running the same playbook or template repeatedly yields identical device state. Declarative templates plus diffs achieve this; raw command scripts generally do not.

Commit-confirmed

Two-step configuration change: the device applies edits and reverts automatically unless the operator confirms within a timer. It protects remote changes that could break management reachability.

Streaming telemetry

Model-driven push of operational data on change or at a dial-out interval, replacing periodic SNMP polling. It scales better and gives finer granularity for monitoring.

Unicast RPF strict mode

Anti-spoofing check that drops a packet unless its source address is reachable through the interface it arrived on. Loose mode only verifies the source exists in the routing table.

DHCP snooping

Builds a trusted binding table of MAC, IP, VLAN and port from DHCP exchanges. Untrusted ports cannot offer DHCP, and the bindings feed IP Source Guard and Dynamic ARP Inspection.

IPv6 RA Guard

First-hop security feature that blocks router advertisements arriving on untrusted access ports, preventing rogue devices from becoming the default gateway through SLAAC.

IPsec ESP

Encapsulating Security Payload provides confidentiality through encryption plus integrity and authentication. IKE negotiates the SAs; AH, by contrast, offers integrity without encryption.