OSPF
Open Shortest Path First (OSPF) is a link state routing protocol that was developed for IPv4 and later IPv6 networks and is based on the Shortest Path First (SPF) algorithm. OSPF is an Interior Gateway Protocol (IGP).
OSPF Version 2 is defined in RFC 2328 for IPv4.
The updates for IPv6 are specified as OSPF Version 3 in RFC 5340.
For our entire OSPF course, take a look here:
https://networklessons.com/ospf
Basics
- OSPF packet types
- OSPF Path selection
- OSPF router ID
- OSPF Why it is not suitable for use on the Internet
- OSPF loop prevention
- OSPF ABR and Loop Prevention
Neighbor Adjacency
Before OSPF routers can exchange LSAs, we have to form a neighbor adjacency.
- OSPF requirements for forming adjacency
- OSPF DR BDR election and neighbor adjacencies
- OSPF DR BDR election criteria
- OSPF DR BDR election process
- OSPF duplicate router IDs
- OSPF Hello packets unicast and multicast
- OSPF immediate hello packet
- OSPF master slave election
- OSPF network types
Advertise
Notes related to how OSPF can advertise network information.
LSAs
OSPF uses Link State Advertisements (LSA) to advertise routing information.
- OSPF ABR Type 3 LSA filtering using access lists
- OSPF Determining which LSA is newer
- OSPF LSA Recursion
- OSPF LSA Sequence Numbers
- OSPF LSA Types
- OSPF Type 4 LSA
- OSPF Incremental SPF and receipt of LSAs
Areas
Everything related to OSPF areas.
- OSPF backbone area 0
- OSPF why is a backbone area 0 necessary
- OSPF - Stub areas and allowed LSAs
- OSPF area inactive
- OSPF area notation
- OSPF area type mismatch
- OSPF Discontiguous Area 0
- OSPF within what area is an OSPF router considered to be
- OSPF NSSA ABR advertises default route
Security
Notes related to making OSPF more secure.
IPv6
OSPFv2 is for IPv4. OSPFv3 supports both IPv4 and IPv6.
- OSPFv2 and OSPFv3 comparison
- OSPFv3 communication between routers and next hop addresses
- OSPFv3 instance ID
- OSPF router ID in an IPv6 environment
Advanced Features
Advanced features of OSPF that don't belong to any of the other topics.
- LFA, remote LFA, and how they work together in OSPF(
- OSPF sham-link
- OSPF sham-link cost
- VRF capability vrf-lite command
- Route-map matching OSPF router ID
- OSPF SPF Scheduling and throttling timers
Troubleshooting
How to troubleshoot OSPF when you can't form neighbor adjacencies or exchange routing information.
Misc
A collection of miscellaneous topics.
- OSPF IS-IS comparison
- OSPF in a GRE multipoint environment
- OSPF IP Unnumbered
- OSPF extent of reconvergence process
- OSPF Forwarding Address
- OSPF metric sum of outgoing interface costs
- OSPF Routing Bit
- OSPF where do you configure a virtual link
Links:
Links to this page:
- home
- BFD - with multiple routing protocols
- BGP - redistributing iBGP routes into an IGP
- BGP Route Reflector
- BGP
- Bidirectional Forwarding Detection (BFD)
- Career study advice
- CoPP - Best practices and operation
- DMVPN - OSPF and multiple areas
- DMVPN - Phase 2 BGP peerings
- DMVPN - Phase 2 EIGRP neighbor adjacencies
- DMVPN - Phase 2 OSPF neighbor adjacencies
- DMVPN - What is the best routing protocol to use
- DMVPN - using a default route
- DMVPN dual hub single cloud
- DMVPN
- Distribute-lists - using route maps to set attributes
- EGP
- EIGRP - Advertised metric is cumulative
- EIGRP - Source of values for metric calculation
- EIGRP unequal cost load balancing
- FHRP - interaction with routing protocols
- GRE - Recursive routing error
- IOS key chain feature
- IP Addressing on a Router
- IPv4 - header protocol field
- IPv4 point to point addresses
- IS-IS - DIS and Pseudonode
- IS-IS
- Interface speed and bandwidth
- Interior Gateway Protocol (IGP)
- LFA - Topology Independent LFA
- LFA, remote LFA, and how they work together in OSPF
- Loop-Free Alternate (LFA) Fast Reroute (FRR)
- Loop-Free Alternate (LFA) and remote LFA
- MPLS - L3VPN BGP OSPF Redistribution
- MPLS - multiarea OSPF in the core
- MPLS Label Edge Router
- MPLS advertising multiple customer subnets
- MPLS-TE - why are IGPs necessary
- Multi-Topology Routing
- Multicast - Local Network Control Block
- Multicast - PIM
- Multicast local subnetwork address range
- Network - Discontiguous
- Network - Flapping
- Network - control plane
- Networks - Underlay Network
- OSPF - Advertising point to multipoint networks
- OSPF - Cost of summarized routes
- OSPF - DR-BDR election per broadcast domain
- OSPF - DR-BDR election priority of zero
- OSPF - ECMP across two different areas
- OSPF - Enabling authentication
- OSPF - HMAC-SHA Extended Authentication
- OSPF - Link State Updates (LSUs)
- OSPF - MPLS SuperBackbone
- OSPF - NBMA neighbors listen on 224.0.0.5
- OSPF - NSSA P-bit
- OSPF - Propagation of routes between areas
- OSPF - Stub areas and allowed LSAs
- OSPF - Type1 LSA
- OSPF - Update pacing timers
- OSPF - default-information originate always command
- OSPF - distribute-list filtering
- OSPF - manual neighbor configuration
- OSPF - point-to-multipoint network type
- OSPF - route filtering
- OSPF - route summarization
- OSPF - summary-address nssa-only on an ABR
- OSPF - what triggers a DR-BDR election
- OSPF ABR Type 3 LSA filtering using access lists
- OSPF ABR and Loop Prevention
- OSPF Authentication for v2 and v3
- OSPF DR BDR election and neighbor adjacencies
- OSPF DR BDR election criteria
- OSPF DR BDR election process
- OSPF Design - When to create new instance
- OSPF Determining which LSA is newer
- OSPF Discontiguous Area 0
- OSPF Forwarding Address
- OSPF Hello packets unicast and multicast
- OSPF IP Unnumbered
- OSPF IS-IS comparison
- OSPF Incremental SPF and receipt of LSAs
- OSPF LSA Recursion
- OSPF LSA Sequence Numbers
- OSPF LSA Types
- OSPF NSSA ABR advertises default route
- OSPF Path selection
- OSPF Routing Bit
- OSPF SPF Scheduling and throttling timers
- OSPF TTL Security Check
- OSPF Troubleshooting
- OSPF Type 4 LSA
- OSPF Type 5 LSA
- OSPF Type 7 LSA
- OSPF Why it is not suitable for use on the Internet
- OSPF advertising loopback network
- OSPF area inactive
- OSPF area notation
- OSPF area type mismatch
- OSPF backbone area 0
- OSPF default metric values
- OSPF design - when to create a new area
- OSPF does not redistribute default route
- OSPF downheap LSA
- OSPF extent of reconvergence process
- OSPF immediate hello packet
- OSPF in a GRE multipoint environment
- OSPF loop prevention
- OSPF message options field
- OSPF metric sum of outgoing interface costs
- OSPF modifying the router ID
- OSPF network command
- OSPF network types
- OSPF non directly connected neighbor adjacencies
- OSPF packet types
- OSPF point to point network type for Ethernet
- OSPF requirements for forming adjacency
- OSPF router ID in an IPv6 environment
- OSPF router ID
- OSPF sham-link cost
- OSPF sham-link
- OSPF virtual link and ABRs
- OSPF where do you configure a virtual link
- OSPF why is a backbone area 0 necessary
- OSPF within what area is an OSPF router considered to be
- OSPFv2 and OSPFv3 comparison
- OSPFv3 - router ospfv3 command
- OSPFv3 communication between routers and next hop addresses
- OSPFv3 instance ID
- Passive interface
- Prefix Lists
- Protocols with LFA support
- QoS - Classification by IP
- QoS - effects of bandwidth interface command
- RIP
- Route-map matching OSPF router ID
- Routers - what is a loopback interface
- Routing - Difference between IGPs and EGPs
- Routing - Administrative Distance
- Routing - Dynamic routing protocols
- Routing - How the routing table is populated
- Routing - Link State Routing Protocols
- Routing - Link-State vs Distance-Vector routing protocols
- Routing - Link-state routing protocol use cases
- Routing - address-family
- Routing - fully specified route
- Routing - ip default-network command
- Routing - link-local IPv6 next hop address needs exit interface
- Routing - network vs redistribute connected commands
- Routing - redistribute command
- Routing - route tagging
- Routing - seed metrics
- Routing NX-OS passive-interface default
- Routing Table
- Routing what if the administrative distance is the same
- Time to live
- Upgrade your R&S skills to modern networking
- VRF capability vrf-lite command