OSPF
Open Shortest Path First (OSPF) is a link-state routing protocol that was developed for IP 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 - attributes and path selection
- 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
- 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
- IS-IS - DIS and Pseudonode
- IS-IS
- Interface speed and bandwidth
- Interior Gateway Protocol (IGP)
- LFA, remote LFA, and how they work together in OSPF
- 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 local subnetwork address range
- Network - control plane
- OSPF - Advertising point to multipoint networks
- OSPF - Cost of summarized routes
- OSPF - DR-BDR election priority of zero
- OSPF - ECMP across two different areas
- OSPF - HMAC-SHA Extended Authentication
- OSPF - NSSA P-bit
- OSPF - Stub areas and allowed LSAs
- OSPF - Type1 LSA
- 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 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 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 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 communication between routers and next hop addresses
- OSPFv3 instance ID
- Passive interface
- Protocols with LFA support
- 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 - 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 - 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