JNCIS-ENT study guide
JNCIS-ENT · Work through your exam, one topic at a time.
JNCIS-ENT - exam code JN0-352 - is the specialist-level certification in Juniper Networks' Enterprise Routing and Switching track. It sits between JNCIA-Junos and JNCIP-ENT and is designed for experienced networking professionals with beginner-to-intermediate knowledge of routing and switching implementations in Junos. The JNCIS-ENT study guide has 9 sections and about 3,026 words.
01Layer 2 Switching and VLANs
Junos splits VLAN configuration into a definition and a membership decision. set vlans BLUE vlan-id 10 defines the VLAN and its 802.1Q tag; the port decides how frames enter it with interface-mode access or interface-mode trunk (older non-ELS EX code still says port-mode ).
342 words, about 2 min02Spanning Tree
On EX and QFX, RSTP (802.1w) is the usual choice: enable it with set protocols rstp interface all or per interface. RSTP computes one topology that serves every VLAN.
342 words, about 2 min03Layer 2 Security
Layer 2 attacks target ARP, DHCP, MAC tables, and broadcast capacity, so Junos exposes a matching set of features. DHCP snooping ( examine-dhcp on a VLAN) builds a binding table of MAC, IP, lease, and port.
333 words, about 2 min04Protocol Independent Routing
Protocol independent routing covers the pieces that do not belong to a dynamic protocol: static routes, aggregates, generated routes, martian filters, routing instances, and filter-based forwarding. A static route ( set routing-options static route 10.0.0.0/8 next-hop 192.0.2.1 ) can carry preference and metric , and a route with several next hops can use qualified-next-hop with a different preference per next hop for primary/backup behaviour.
339 words, about 2 min05OSPF
OSPF is enabled per area per interface: set protocols ospf area 0.0.0.0 interface ge-0/0/0.0 . Every router in an area builds an identical link-state database from type 1 (router) and type 2 (network, from the DR) LSAs.
369 words, about 2 min06IS-IS
IS-IS runs directly over Layer 2, so it needs no IP address to form an adjacency; identity comes from the NET: a 1-to-13-byte area, a 6-byte system ID, and the NSEL 00 , for example 49.0001.1921.6800.1001.00 . The system ID must be unique (usually derived from the loopback) and changing it breaks existing adjacencies.
350 words, about 2 min07BGP
eBGP peers across ASes and normally needs multihop (plus local-address ) when the peers are not directly connected, because the default TTL is 1. iBGP peers inside one AS must reach each other's next hops through the IGP, and iBGP does not rewrite the next hop by default, so next-hop-self on edge routers and route reflectors is essential.
321 words, about 2 min08Tunnels
Junos tunnel interfaces are named by type: gr- for GRE, ip- for IP-in-IP, vt- for virtual tunnels, lt- for logical tunnels, and st- . Configuration binds source and destination, then treats the tunnel as an ordinary interface: set interfaces gr-0/0/0 unit 0 tunnel source 10.1.1.1 destination 10.2.2.2 family inet address 192.168.1.1/30 .
311 words, about 2 min09High Availability
set protocols vrrp interface ge-0/0/0.0 virtual-address 10.0.0.254 gives hosts a shared gateway. Priority defaults to 100; the highest priority becomes master, and a tie is broken by the highest interface IP address.
319 words, about 2 min