Nokia MPLS flashcards

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

SR OS base router vs VPRN

The base router holds global routes and interfaces; VPRN instances hold per-VPN routing tables. Routes cross only via explicit export/import policies, never automatically.

IS-IS NET address

A Network Entity Title combines area ID, system ID, and NSEL. Level 1 routers stay intra-area; Level 2 forms the backbone; L1/L2 routers set the ATT bit to advertise a default to L1-only neighbors.

OSPF NSSA vs stub area

A stub area blocks Type 5 external LSAs; an NSSA also blocks Type 5 but carries Type 7 LSAs internally, which the ABR translates to Type 5 when leaking into the backbone.

BGP best-path first criteria

SR OS selects highest local preference, then shortest AS path, then lowest origin, then lowest MED (same neighbor AS unless always-compare-med), then eBGP over iBGP, then lowest IGP metric.

SR OS route preference defaults

Lower preference wins: direct/local 0, static 5, OSPF internal 10, IS-IS L1 15, IS-IS L2 18, RIP 100, OSPF external 150, BGP 170.

Prefix-SID and SRGB

A prefix-SID is an index into the Segment Routing Global Block. All routers must agree on SRGB size for the same index to yield the same label value across the domain.

ECMP in SR OS

ECMP is enabled per interface with ecmp max-paths. Hashing uses configurable fields such as the IP 5-tuple or MPLS label stack to spread flows across equal-cost next hops.

SR OS service types

Epipe is point-to-point, VPLS is multipoint bridged, VPRN is routed VPN, IES is routed with SAPs, and EVPN variants provide EVPN-VPLS and EVPN-Epipe services.

SAP vs SDP

A SAP binds a service to a local port or LAG, written as port:encap (e.g., 1/1/1:100). An SDP binds a service to a far-end node over MPLS or GRE transport.

VPLS split-horizon rule

By default a frame received from one SDP is not forwarded to another SDP in the same VPLS. This prevents bridging loops between pseudowires without relying on STP.

LAG and LACP

A link aggregation group bundles member ports; LACP negotiates membership. In SR OS the LAG must be administratively enabled before member ports can come into service.

MSTP CIST root

MSTP maps VLANs to instances. The CIST root is the bridge with the lowest bridge ID across all instances, and each MST instance has its own regional root.

EVPN route types

Type 2 advertises MAC/IP, Type 3 is inclusive multicast (IMET) for BUM flooding, Type 4 is Ethernet segment, and Type 5 is IP prefix. Type 3 is required for EVPN-VPLS BUM.

QinQ SAP notation

QinQ stacks an outer S-tag over customer C-tags (802.1ad). In SR OS this appears as a qinq SAP such as 1/1/1:100.* on a dot1q-encapsulated port.

Aggregation layer boundary rule

Access rings typically run Layer 2 (VPLS/STP) while distribution runs Layer 3 (VPRN/IS-IS). Placing the L2/L3 boundary close to access limits broadcast domains and STP scope.

NSP architecture layers

NSP combines NSP Fabric for network modeling, NSP NFM-P for fault and performance management of IP/MPLS, and NSP Network Automation for intent-based provisioning.

NSP southbound interfaces

NSP talks to SR OS via model-driven interfaces such as NETCONF/MD-CLI or gNMI. SNMP is used for legacy polling but not for intent-based configuration.

SR OS YANG modules

Nokia publishes YANG modules such as nokia-conf, nokia-state, and nokia-li. They let controllers render configuration as a model instead of parsing CLI text.

Intent-based automation

An intent such as creating a VPN between sites is decomposed by NSP into device-level configuration. Validation is against the YANG model, not by parsing CLI output.

gNMI operations

gNMI supports Get, Set, Subscribe, and Capabilities. Streaming Subscribe replaces periodic SNMP polling for high-frequency counters and state changes.

SR OS telemetry setup

Streaming telemetry is configured under system grpc or telemetry. The collector endpoint and subscription paths such as /state/router are set per subscription.

Automation idempotency

Re-applying the same intent must produce no change. NSP diffs the intent against the current model and pushes only deltas, so a no-op intent yields no config change.

SR OS filter types

SR OS supports IP, MAC, and IPv6 filters. Entries are evaluated top-down, first match wins, and an implicit default action applies after the last entry.

Filter actions

Filter entries can forward, drop, or forward with a redirect to a next hop or policer. Filters can also mark DSCP or assign a forwarding class.

CPM filter purpose

A CPM filter configured under system security cpm-filter protects the management and control processor from DoS. It is separate from filters applied to transit traffic.

uRPF strict vs loose

Strict uRPF requires the packet to arrive on the interface used to reach the source. Loose uRPF accepts any route to the source; strict is used at the edge.

BGP and OSPF authentication

SR OS supports MD5 for BGP and OSPF authentication keys, and HMAC-SHA for TCP-AO. Keys must match on both peers or the session drops.

Management plane hardening

SSH and TLS replace Telnet and HTTP. SNMPv3 with auth and priv (SHA plus AES) is required where SNMP is used, and local users get profile-based privileges.

Lawful intercept in SR OS

LI uses an x-intercept source (mirror or filter based) and an x-intercept destination with mediation handoff. It is separate from normal port mirroring.

DWDM channel spacing

ITU-T G.694.1 anchors the DWDM grid at 193.1 THz. At 1550 nm, 100 GHz spacing equals 0.8 nm, 50 GHz equals 0.4 nm, and 25 GHz equals 0.2 nm.

OSNR cascade penalty

Each amplifier stage degrades optical SNR. For N identical spans the cascade penalty is roughly 10*log10(N) dB, so longer chains need higher per-span launch power or fewer amps.

Coherent modulation reach

Coherent DSP compensates chromatic dispersion and PMD electrically. Higher-order modulation such as 16QAM doubles capacity versus QPSK but roughly halves reach.

IPoDWDM 400ZR reach

IPoDWDM places coherent pluggables such as 400ZR or OpenZR+ directly in routers, removing a transponder layer but limiting reach to roughly 80 to 120 km for 400ZR.

EVPN-VXLAN DCI overlay

EVPN-VXLAN is the standard data center overlay. A 24-bit VXLAN VNI maps to an EVPN VPLS instance, and anycast gateway avoids traffic tromboning across the fabric.

DCI sub-50ms protection

Sub-50ms DCI protection requires optical protection switching (OLP) or MPLS FRR. IGP convergence alone is too slow, and dual-diverse conduits plus BFD improve failure detection.