Networking Fundamentals
8-10%of exam
Junos OS Fundamentals
7-10%of exam
User Interfaces
18-22%of exam
Configuration Basics
18-23%of exam
Monitoring + Maintenance
12-15%of exam
Routing Fundamentals
15-20%of exam
Policy + Firewall Filters
8-12%of exam
Quick Facts
- Exam
- JN0-106
- Credential
- JNCIA-Junos
- Questions
- 65 multiple choice
- Time
- 90 min
- Cost
- $200 USD
- Validity
- 3 years
- Delivery
- Pearson VUE
- Result
- Pass/fail shown
Networking Basics
- Collision domain
- Per switch port
- Broadcast domain
- Per VLAN/subnet
- Switch
- Layer 2 forwarding
- Router
- Layer 3 forwarding
- MAC address
- 48-bit Layer 2
- IPv4
- 32-bit address
- IPv6
- 128-bit address
Addressing + Subnetting
- /24
- 256 addresses
- /30
- Point-to-point link
- Network bits
- Left of mask
- Host bits
- Right of mask
- Longest match
- Most specific wins
- Connectionless
- UDP no handshake
- Connection-oriented
- TCP handshake
RE vs PFE
RE thinks, PFE forwards
RE = control planePFE = data planeRE runs protocolsPFE moves packets
Transit vs Exception
Transit
- Through device
- PFE only
- Forwarded
Exception
- To/from RE
- Protocol/local
- Punted up
Pass vs process
Junos Architecture
- RE
- Routing engineControl plane
- PFE
- Forwarding engineData plane
- Control plane
- Protocols + mgmt
- Forwarding plane
- Packet forwarding
- FreeBSD kernel
- Junos foundation
- Internal link
- RE to PFE
- Single train
- One Junos image
Traffic Processing
- Transit traffic
- PFE forwards through
- Exception traffic
- Sent to RE
- Local traffic
- Destined to device
- Protocol traffic
- OSPF/BGP to RE
- ICMP to RE
- Exception path
- Forwarding table
- PFE lookup copy
Commit Flow
Edit, compare, check, commit, confirm
set/deleteshow | comparecommit checkcommitrollback if bad
Candidate vs Active
Candidate
- Being edited
- Not yet live
- Discardable
Active
- Running config
- Live on device
- After commit
Edit then commit
Which CLI Mode
- Prompt ends >→Operational mode(show/monitor)
- Need to change config→configure(Enter config)
- Prompt ends #→Configuration mode(set/delete)
- Run op command in config→run command(No exit needed)
- Done editing→commit(Activate config)
- Leave config mode→exit(Back to >)
CLI Modes + Navigation
- Operational mode
- Prompt ends >
- Configuration mode
- Prompt ends #
- configure
- Enter config mode
- exit / quit
- Leave current level
- top
- Go hierarchy root
- up
- Move one level
- edit
- Move into level
Operational vs Config
Operational
- Prompt >
- show/monitor
- View state
Configuration
- Prompt #
- set/delete
- Change device
Look vs change
Which Commit Action
- Apply changes now→commit
- Validate only→commit check
- Risky remote change→commit confirmed(Auto rollback)
- Change worked→commit(Confirm it)
- Add commit note→commit comment
- Schedule later→commit at
Help + Filtering
- ?
- Context help list
- Spacebar
- Complete command
- Tab
- Complete variable
- | match
- Show matching lines
- | count
- Count output lines
- | display set
- Show as set
- | no-more
- Disable pager
commit vs commit confirmed
commit
- Permanent now
- No timer
- Stays active
commit confirmed
- Temporary
- Auto rollback
- Confirm to keep
Permanent vs safety net
Recover Config State
- Discard candidate edits→rollback 0
- Undo last commit→rollback 1
- Go further back→rollback n(Up to 49)
- Device broken badly→rollback rescue
- Forgot to commit→commit(After rollback)
- Reset everything→load factory-default
Config Management
- set
- Add config statement
- delete
- Remove config statement
- show | compare
- Candidate vs active
- commit
- Activate candidate
- commit check
- Validate no apply
- rollback 0
- Discard candidate edits
- rollback n
- Previous active config
J-Web
- J-Web
- Browser GUI
- HTTPS access
- Secure J-Web
- Dashboard
- Device status view
- Point-and-click
- GUI configuration
- CLI parity
- Same commit model
Interface Format
type dash FPC slash PIC slash port
ge = Gigabitxe = 10Gfxp0 = mgmtlo0 = loopback
Initial Setup
- Factory default
- Out-of-box config
- root user
- No default password
- set root-authentication
- Required first commit
- Console port
- Initial CLI access
- load factory-default
- Reset candidate
- Hostname
- set system host-name
User Authentication
- Login class
- Permission set
- Predefined classes
- operator/read-only/super-user
- Local password
- On-box auth
- RADIUS
- External auth server
- TACACS+
- External auth server
- Authentication order
- Method fallback list
Interfaces + System Services
- NTP
- Time synchronization
- SNMP
- Monitoring + traps
- DNS
- Name resolution
- Config groups
- Reusable config blocks
- apply-groups
- Inherit group config
- unit
- Logical interface
- family inet
- IPv4 on unit
Logging Archival Rescue
- syslog
- System event logging
- messages file
- Default syslog file
- traceoptions
- Per-feature debugging
- Config archival
- Auto save on commit
- Rescue config
- Known-good fallback
- rescue save
- Store rescue config
- rollback rescue
- Load rescue config
Interface Naming
- ge-0/0/0
- Gigabit Ethernet port
- xe-
- 10-Gigabit Ethernet
- et-
- 40/100-Gigabit Ethernet
- ae0
- Aggregated Ethernet
- lo0
- Loopback interface
- fxp0
- Management interface
- type-fpc/pic/port
- Naming format
Monitoring Commands
- show interfaces
- Interface status/stats
- show route
- Routing table
- show chassis
- Hardware status
- show system uptime
- Boot + commit time
- show log
- View log file
- monitor interface
- Live counters
- monitor traffic
- Packet capture
Network Tools
- ping
- Reachability test
- traceroute
- Path discovery
- show arp
- IPv4 MAC bindings
- clear interfaces statistics
- Reset counters
- input/output errors
- Interface fault counters
Maintenance + Upgrades
- request system software add
- Install Junos image
- request system reboot
- Safe reboot
- request system halt
- Safe shutdown
- request system snapshot
- Backup boot media
- Password recovery
- Single-user boot
- Recovery requires console
- Physical access
Preference Order
Direct 0, Static 5, OSPF 10, RIP 100, BGP 170
Lower winsDirect/Local 0Static 5OSPF int 10BGP 170
RIB vs FIB
RIB
- Routing table
- On RE
- All routes
FIB
- Forwarding table
- On PFE
- Active only
Choose vs forward
Which Route Wins
- Compare two routes→Lowest preference(Tiebreak first)
- Static vs OSPF→Static(5 beats 10)
- OSPF vs BGP→OSPF(10/150 beats 170)
- Same preference→Protocol metric(Lower wins)
- Need active route→show route(Asterisk marked)
- What PFE uses→Forwarding table(FIB only)
Route Tables + Forwarding
- RIB
- Routing table (RE)
- FIB
- Forwarding table (PFE)
- inet.0
- IPv4 unicast RIB
- inet6.0
- IPv6 unicast RIB
- Active route
- Installed into FIB
- show route
- Display RIB
- show route forwarding-table
- Display FIB
Static vs Dynamic
Static
- Manual config
- Preference 5
- No protocol
Dynamic
- Learned via protocol
- Auto adapts
- Higher preference
Manual vs learned
Route Preference Values
- Direct
- 0Most preferred
- Local
- 0
- Static
- 5
- OSPF internal
- 10
- IS-IS L1 internal
- 15
- RIP
- 100
- OSPF external
- 150
- BGP
- 170
Static + Routing Instances
- static route
- Manual next hop
- next-hop
- IP forwarding target
- discard
- Drop silently
- reject
- Drop send ICMP
- 0.0.0.0/0
- Default route
- Routing instance
- Separate route table
- Lower preference
- More preferred route
Filter Default
No match means discard
First match winsImplicit denyOrder mattersthen accept needed
Routing Policy vs Filter
Routing policy
- Acts on routes
- Import/export
- Control plane
Firewall filter
- Acts on packets
- Match traffic
- Data plane
Routes vs packets
Routing Policy
- Import policy
- Routes into RIB
- Export policy
- Routes out advertised
- Term
- from + then block
- from
- Match condition
- then accept
- Allow route
- then reject
- Deny route
- Default policy
- Per-protocol behavior
Firewall Filters
- Firewall filter
- Packet match action
- Filter term
- from + then
- then accept
- Permit packet
- then discard
- Drop packet
- Implicit deny
- Unmatched dropped
- First match
- Top-down evaluation
- uRPF
- Source address check
Common Traps
Edit vs apply
set edits candidate ≠ commit makes active
rollback 0 vs rollback 1
0 discards candidate ≠ 1 prior active config
RIB vs FIB
RIB on RE ≠ FIB on PFE
Preference vs metric
Preference compared first ≠ Metric breaks ties
Lower preference better
Lower = preferred ≠ Not highest value
Policy vs filter
Policy on routes ≠ Filter on packets
commit confirmed timer
Auto rolls back ≠ Must commit again
Last Minute
- 1.Exam = JN0-106 now
- 2.65 questions, 90 minutes
- 3.set edits; commit activates
- 4.rollback 0 = discard candidate
- 5.commit confirmed auto-rolls back
- 6.Direct 0, Static 5, OSPF 10
- 7.BGP preference = 170
- 8.Lower preference = preferred
- 9.RIB = RE; FIB = PFE
- 10.Policy = routes; filter = packets
- 11.Filter unmatched = discard
- 12.fxp0 = management interface
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