JNCIP-ENT flashcards

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

OSPF LSA Type 5

AS External LSA originated by an ASBR to advertise routes redistributed into OSPF from outside the domain. It is flooded throughout the OSPF domain except into stub and NSSA areas.

OSPF virtual link

A logical tunnel through a transit area that connects a non-backbone area to area 0 when the ABR lacks a direct backbone connection. It must transit a non-stub area.

IS-IS wide metrics

24-bit metric TLVs (22, 23, 135) that allow interface metrics above the 6-bit narrow limit of 63. Required for traffic engineering and for links with metrics greater than 63.

OSPF DR/BDR election

Per multi-access segment, non-preemptive. Highest interface priority wins (0 means never DR); ties break on highest router ID. The DR floods LSAs to all neighbors on the segment.

BGP local preference

A well-known discretionary attribute used only within an AS. Higher values are preferred. It is set on iBGP edge routers to influence outbound path selection across the entire AS.

BGP MED

Multi-Exit Discriminator, an optional non-transitive attribute. Lower values are preferred. It suggests to an external peer which entry point to use into the local AS.

BGP route reflector

An iBGP router allowed to reflect routes from clients to other clients and non-clients. It removes the full-mesh requirement. Cluster ID and originator ID prevent loops.

BGP next-hop-self

A configuration on an iBGP edge router that rewrites the next hop of reflected or learned routes to its own address, ensuring internal peers can resolve the next hop.

PIM-SM shared tree

The (*,G) tree rooted at the Rendezvous Point. Last-hop routers join toward the RP. After receiving traffic, they may switch to the shortest-path (S,G) tree to the source.

PIM RPF check

A multicast router accepts a packet only if it arrives on the interface that the unicast route to the source selects. A failed check drops the packet and prevents loops.

IGMPv3 source-specific join

IGMPv3 lets a host request traffic from specific sources for a group. This enables PIM-SSM, where the last-hop router sends an (S,G) join directly to the source without an RP.

MSDP

Multicast Source Discovery Protocol connects PIM-SM domains by exchanging source-active (S,G) messages between RPs, enabling inter-domain multicast without a shared RP.

STP root bridge election

The switch with the lowest bridge ID (priority plus MAC) becomes root. Default priority is 32768; lowering it on one switch forces that switch to become root.

RSTP edge port

A port configured as an edge (PortFast) port transitions directly to forwarding and does not generate topology changes. It should connect only to end hosts, not switches.

MSTP region

A group of switches sharing the same region name, revision, and VLAN-to-instance mapping. Within a region, MSTP runs one spanning tree per instance instead of per VLAN.

BPDU Guard

A feature that err-disables a port if it receives a BPDU. It is applied to edge ports to prevent accidental or malicious switch connections from affecting the spanning tree.

802.1X supplicant

The client device that requests network access. It runs EAPOL to the authenticator switch, which relays EAP to the RADIUS server for authentication and authorization.

MAB authentication

MAC Authentication Bypass. The switch sends the device's MAC address to RADIUS as both username and password for devices that cannot run 802.1X, such as printers.

Dynamic VLAN assignment

RADIUS returns Tunnel-Type=13, Tunnel-Medium-Type=6, and Tunnel-Private-Group-ID=VLAN ID. The authenticator places the port into that VLAN after successful authentication.

DHCP snooping

A switch feature that trusts only configured uplink ports for DHCP server messages. It blocks rogue DHCP servers and builds a binding table used by IP Source Guard and DAI.

LLDP-MED voice VLAN

An extension to LLDP that advertises voice VLAN and QoS information to IP phones. The phone tags voice traffic with 802.1Q and can pass PC data untagged.

PoE 802.3at

PoE+ standard delivering up to 30 W at the PSE (25.5 W at the PD) over two pairs. It extends 802.3af (15.4 W) for devices such as video phones and access points.

G.711 codec bandwidth

A 64 kbps voice codec. With IP/UDP/RTP headers, a single call typically consumes about 80-87 kbps. It offers high voice quality but more bandwidth than G.729.

Voice QoS markings

RTP media is marked EF (DSCP 46) and call signaling CS3 (DSCP 24). These markings should be trusted at the phone or access port and prioritized in the queueing scheme.

DSCP EF

Expedited Forwarding, DSCP 46 (binary 101110). It is the recommended per-hop behavior for voice RTP. It is typically placed in a strict-priority or low-latency queue.

AF class formula

Assured Forwarding codepoints are AFxy, where x is class 1-4 and y is drop precedence 1-3. The DSCP value equals 8*x + 2*y, e.g., AF41 = 34.

Trust boundary

The point in the network where QoS markings are accepted from downstream devices. Typically set at the access port or IP phone; untrusted traffic is re-marked to a default class.

WRED

Weighted Random Early Detection. It drops packets probabilistically before a queue fills, using per-DSCP drop profiles, to signal congestion to TCP flows and avoid global synchronization.

EVPN Type 2 route

MAC/IP Advertisement route. It carries MAC address, optional IP, Ethernet tag, MPLS label or VNI, and extended communities. It enables MAC learning and mobility across the EVPN.

EVPN Type 5 route

IP Prefix route. It advertises IP prefixes (with MPLS label or VNI) for L3VPN-style routing in EVPN, supporting symmetric IRB and prefix-based forwarding.

EVPN multihoming ESI

Ethernet Segment Identifier identifies a multihomed segment. Type 4 routes elect the designated forwarder; All-Active mode uses LAG across PEs for redundancy and load sharing.

EVPN anycast gateway

All leaf switches use the same MAC and IP for the distributed IRB gateway. This avoids traffic tromboning and lets VMs move between leaves without changing their default gateway.