Huawei HCIE-Datacom flashcards

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

OSPF Type 7 LSA

An NSSA external LSA flooded only within a not-so-stubby area. The ABR with the highest router ID translates it to a Type 5 LSA for the rest of the domain.

OSPF virtual link

A logical tunnel through a transit area that connects a remote area to the backbone. Both endpoints must be ABRs, and the transit area cannot be a stub area.

OSPF DR/BDR election

On broadcast and NBMA networks, the router with the highest interface priority wins; ties break by highest router ID. Priority 0 means the router never becomes DR.

OSPF stub area

An area that blocks Type 5 external LSAs. The ABR injects a default route as a Type 3 LSA, reducing the LSDB size on internal routers.

IS-IS NET address

A Network Entity Title in the form of an NSAP, typically 49.0001.xxxx.xxxx.xxxx.00. The last byte is the NSEL, which must be 00 for a router.

IS-IS DIS election

On broadcast links the Designated Intermediate System is chosen by highest interface priority, then highest subnetwork point of attachment (SNPA/MAC). Unlike OSPF, preemption is immediate.

BGP Local Preference

A well-known discretionary attribute propagated within an AS. Higher values are preferred, and it is the second tiebreaker after Weight in best-path selection.

BGP MED

Multi-Exit Discriminator, an optional non-transitive attribute. Lower values are preferred, and it is compared only among paths from the same neighboring AS by default.

BGP route reflector rules

Routes from a client go to clients and non-clients; routes from a non-client go only to clients. Originator_ID and Cluster_List prevent reflection loops.

BGP AS_PATH loop prevention

A router rejects any route whose AS_PATH already contains its own AS number. This is the primary loop-prevention mechanism for eBGP, checked before best-path selection.

MPLS implicit-null label

Label value 3, assigned by the egress router for directly connected prefixes. The penultimate hop pops the label so the egress router receives a plain IP packet.

MPLS LDP label distribution

LDP uses UDP 646 for discovery and TCP 646 for session establishment. Labels are advertised downstream-on-demand, mapping FECs to label bindings.

VXLAN VNI size

A 24-bit identifier allowing roughly 16 million segments, carried in the VXLAN header inside UDP port 4789. It maps to a bridge domain on the VTEP.

EVPN Type 2 route

A MAC/IP advertisement route used for host reachability and ARP suppression in BGP EVPN. It carries the MAC, optional IP, VNI, and next hop.

SRv6 locator

An IPv6 prefix advertised in IGP that represents a group of SIDs. Each SID is a locator plus a function, such as End.DT4 for IPv4 VPN decapsulation.

Segment Routing global block

The SRGB is the label range reserved for global SIDs, default 16000-23999. Each node advertises its SRGB and prefix SID in IGP extensions.

RSTP edge port

A port configured as edge (PortFast) skips listening and learning and enters forwarding immediately. It should only connect to end hosts to avoid loops.

MSTP instance mapping

MSTP maps VLANs to multiple spanning tree instances, each with its own root and topology. This enables load sharing across redundant links.

Eth-Trunk LACP mode

LACP negotiates link aggregation using LACPDUs. Up to 8 links are active; additional links stay in standby and take over if an active link fails.

VRRP virtual MAC

The master responds with MAC 0000-5e00-01XX, where XX is the VRID in hex. This allows hosts to keep a stable gateway MAC during failover.

DHCP snooping trusted port

Only trusted ports may forward DHCP OFFER and ACK messages. Untrusted ports drop server replies, preventing rogue DHCP servers on access ports.

IPSG binding table

IP Source Guard uses the DHCP snooping binding table to permit only matching source MAC-IP pairs on untrusted ports, dropping spoofed traffic.

IPv6 neighbor discovery

ND uses ICMPv6 NS/NA for address resolution and RS/RA for router discovery and SLAAC. It replaces ARP and provides stateless autoconfiguration.

NAT64 with DNS64

NAT64 translates IPv6 to IPv4 using a stateless prefix mapping. DNS64 synthesizes AAAA records from A records so IPv6-only hosts can reach IPv4 servers.

LLQ scheduling

Low Latency Queuing combines a strict-priority queue for voice with CBWFQ for other classes. The priority queue is policed to prevent starvation.

WRED congestion avoidance

Weighted Random Early Detection drops packets probabilistically before the queue is full. It prevents global synchronization and penalizes aggressive flows.

NETCONF transport

NETCONF runs over SSH on TCP port 830 and uses XML-encoded RPCs with YANG data models. It supports candidate configuration and confirmed commit.

gRPC telemetry

Model-driven telemetry streams operational data from devices to a collector using gRPC over HTTP/2, providing push-based, high-frequency monitoring.

RADIUS authentication ports

RADIUS uses UDP 1812 for authentication and authorization and UDP 1813 for accounting. Earlier implementations used UDP 1645 and 1646.

HWTACACS vs RADIUS

HWTACACS runs over TCP 49, encrypts the entire packet body, and separates authentication, authorization, and accounting, which suits device administration.

SNMPv3 security levels

SNMPv3 offers noAuthNoPriv, authNoPriv, and authPriv. authPriv uses both authentication (MD5/SHA) and encryption (DES/AES) for maximum security.

Syslog severity levels

Eight levels from 0 Emergency to 7 Debugging. Lower numbers are more severe, and the configured threshold determines which messages are logged or forwarded.