JNCIS-ENT flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Access port
- A switch port that carries traffic for a single VLAN untagged; frames entering it are assigned to that VLAN and leave without a VLAN tag.
- Trunk port
- A switch port that carries multiple VLANs, tagging frames with 802.1Q VLAN IDs and optionally sending one native VLAN untagged.
- IRB interface
- A Layer 3 interface bound to a VLAN that provides routing between that VLAN and other subnets on Junos switches.
- Q-in-Q tunneling
- A technique that adds an outer service VLAN tag around customer VLAN tags, allowing a provider to transport multiple customer VLANs transparently.
- RSTP port roles
- Root, designated, alternate, and backup; alternate and backup roles provide rapid failover without waiting for STP timers.
- Bridge priority
- A spanning-tree value set in increments of 4096; the lowest value, followed by the lowest MAC address, determines the root bridge.
- MSTP region
- A group of switches sharing the same region name, revision level, and VLAN-to-instance mapping so they run a common MSTP topology.
- Edge port
- An RSTP port connected to an end station; it transitions to forwarding immediately and should not receive BPDUs.
- DHCP snooping
- A Layer 2 security feature that filters DHCP messages on untrusted ports and builds a binding table of leased IP addresses to MAC addresses and VLANs.
- Dynamic ARP inspection
- A security feature that checks ARP packets against DHCP snooping bindings and drops ARP messages with invalid IP-to-MAC mappings.
- IP source guard
- A filter that permits only source IP and MAC combinations found in DHCP snooping bindings, preventing IP address spoofing on access ports.
- Storm control
- A feature that limits broadcast, multicast, or unknown unicast traffic on an interface to a configured bandwidth or packet rate.
- Route preference
- A Junos value used to choose among routes to the same destination from different sources; lower values are preferred.
- Route filter match types
- Exact matches only the stated prefix, longer matches more-specific prefixes, orlonger includes the prefix, and upto sets a maximum length.
- Aggregate route
- A Junos route that is generated only when at least one contributing route is active, summarizing multiple prefixes into one advertisement.
- OSPF LSA types
- Type 1 router, type 2 network, type 3 summary, type 4 ASBR summary, type 5 external, and type 7 NSSA external link-state advertisements.
- OSPF DR election
- The router with highest interface priority becomes designated router; ties go to highest router ID, and priority 0 is never eligible.
- Stub area
- An OSPF area that blocks type 5 external LSAs; reachability to external networks is provided by a default route from the ABR.
- OSPF cost
- Calculated as reference bandwidth divided by interface bandwidth; Junos uses a 100 Mbps reference by default, so faster links need manual adjustment.
- IS-IS NET address
- A network entity title combining area ID, a 6-byte system ID, and an NSEL byte of 00 for routers, such as 49.0001.1921.6800.1001.00.
- IS-IS DIS
- The designated intermediate system on a LAN, elected by highest priority and then highest MAC address, that generates the pseudonode LSP.
- IS-IS levels
- Level 1 routes within an area, Level 2 forms the backbone between areas, and Level 1/2 routers attach an area to the backbone.
- BGP weight
- A local, non-transitive attribute; the route with the highest weight is preferred before all other BGP path selection steps.
- BGP local preference
- A transitive attribute advertised within an autonomous system; higher values are preferred for outbound path selection.
- BGP MED
- A multiexit discriminator sent to neighboring autonomous systems to suggest an entry point; lower values are preferred.
- Route reflector
- An iBGP router that reflects routes from clients to other clients and nonclients, reducing the need for a full iBGP mesh.
- GRE tunnel
- A generic routing encapsulation tunnel using a gr- interface that encapsulates packets in an outer IP and GRE header.
- Tunnel MTU
- The maximum packet size a tunnel interface can carry; encapsulation headers add overhead, so the tunnel MTU is lower than the physical MTU.
- VXLAN VNI
- A 24-bit identifier that maps traffic to a virtual network segment in VXLAN, enabling Layer 2 extension over an IP fabric.
- VRRP master
- The router with the highest VRRP priority that owns the virtual IP and forwards traffic for the virtual router.
- BFD multiplier
- The number of consecutive missed BFD control packets, multiplied by the negotiated interval, before a session is declared down.
- LACP active mode
- A link aggregation mode in which the local device actively sends LACP PDUs to negotiate and maintain a bundle with its peer.