
Both [stub and totally stub areas](/ospf-stub-areas-allowed-lsas) in [OSPF](/ospf) are designed to reduce the amount of [routing](/routing) information within an area, which can improve performance and reduce resource usage. However, they differ in the type of routing information they filter and the use cases they are suited for. Here's a detailed comparison:

| **Feature**                 | **Stub Area**                                                                                                                                                | **Totally Stub Area**                                                                                                                            |
| --------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------ |
| **Definition**              | A stub area prevents [Type-5 LSAs](/ospf-type-5-lsa) (External routes) from being flooded but allows [Type-3 LSAs](/ospf-type-3-lsa) (Inter-area routes).  | A totally stub area prevents both Type-5 (External routes) and most Type-3 LSAs (Inter-area routes) from being flooded.                          |
| **Default Route Injection** | Receives a [default route](/ip-routing-table-default-route) (0.0.0.0/0) from the [ABR](/ospf-area-border-router-abr) to reach external destinations. | Receives a default route (0.0.0.0/0) from the ABR to reach both external and inter-area destinations.                                            |
| **Type of LSAs Allowed**    | Allows [Type-1](/ospf-type-1-lsa), Type-2, and Type-3 LSAs. Type-5 LSAs are blocked.                                                                      | Allows Type-1 and Type-2 LSAs. Blocks Type-3, [Type-4](/ospf-type-4-lsa), and Type-5 LSAs.                                                      |
| **Configuration**           | `area <area-id> stub`                                                                                                                                        | `area <area-id> stub no-summary`                                                                                                                 |
| **Main Use Case**           | Useful when external routes are not needed in the area, but inter-area routes are required.                                                                  | Useful for areas that need minimal routing information and rely on a single default route for all non-local destinations.                        |
| **Traffic Optimization**    | Reduces external route advertisements, optimizing performance for areas with less interest in external destinations.                                         | Maximizes simplicity and performance by drastically reducing routing information, suitable for edge areas with simple connectivity requirements. |
| **Resource Savings**        | Moderate reduction in routing table size and CPU/memory usage.                                                                                               | Significant reduction in routing table size and CPU/memory usage.                                                                                |
| **Example Scenario**        | A branch office that requires access to other OSPF areas but not to external networks.                                                                       | A remote office that connects only to a single central office and relies entirely on default routes.                                             |

## Similarities

1. **Default Route**: Both receive a default route from the ABR.
2. **Filtered LSAs**: Both reduce the size of the routing table by filtering [specific LSAs](/ospf-lsa-types).

## Differences

1. **Type-3 LSAs**: Stub areas allow Type-3 LSAs (inter-area routes), whereas totally stub areas block them.
2. **Configuration Syntax**: Totally stub areas require the `no-summary` keyword, while stub areas do not.

## Links

https://networklessons.com/ospf/introduction-to-ospf-stub-areas
https://networklessons.com/ospf/how-to-configure-ospf-stub-area
https://networklessons.com/ospf/how-to-configure-ospf-totally-stub-area

OSPF Stub Area vs Totally Stub Area

OSPF - OSPFv3 authentication

OSPF - Propagation of routes between areas

OSPF - Stuck in ATTEMPT neighbor state

OSPF - Stuck in ExStart or Exchange states

OSPF - Type 1 LSA

OSPF - Type 5 LSA filtering on an ASBR

OSPF - Update pacing timers

OSPF - capablity vrf-lite

OSPF - control plane vs data plane loops

OSPF - default-information originate always command

OSPF - distance command

OSPF - distribute-list filtering

OSPF - manual neighbor configuration

OSPF - network type mismatch

OSPF - non-zero Forwarding Address example

OSPF - point-to-multipoint network type

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 BDR to DR Transition Time

OSPF DR BDR election and neighbor adjacencies

OSPF DR BDR election criteria

OSPF DR BDR election process

OSPF Database Exchange Process Master Slave Election

OSPF Design - When to create new instance

OSPF Determining which LSA is newer

OSPF Discontiguous Area 0

OSPF Do Not Age (DNA) Flag

OSPF E1 E2 N1 N2 routes

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 Persistence with DNA flag

OSPF LSA Recursion

OSPF LSA Sequence Numbers

OSPF LSA Types

OSPF NSSA ABR advertises default route

OSPF Not So Stubby Area NSSA

OSPF Packet Types and Their Transmission Methods

OSPF Path selection

OSPF Prefix Suppression Considerations

OSPF Route Filtering

OSPF Routing Bit

OSPF SPF Scheduling and throttling timers

OSPF Stub areas allowed LSAs

OSPF Summarization Restrictions Within an Area

OSPF TTL Security Check

OSPF Troubleshooting

OSPF Type 3 LSA

OSPF Type 4 LSA

OSPF Type 5 LSA

OSPF Type 7 LSA

OSPF Understanding LSA Aging and Refreshing

OSPF Virtual Link Network Type Considerations

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 duplicate router IDs

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

OSPF

OSPFv2 and OSPFv3 comparison

OSPFv3 - router ospfv3 command

OSPFv3 communication between routers and next hop addresses

OSPFv3 instance ID

Offset-list

PAT (overloading) maximum number of translations per inside global address

PAgP

Feature	Stub Area	Totally Stub Area
Definition	A stub area prevents Type-5 LSAs (External routes) from being flooded but allows Type-3 LSAs (Inter-area routes).	A totally stub area prevents both Type-5 (External routes) and most Type-3 LSAs (Inter-area routes) from being flooded.
Default Route Injection	Receives a default route (0.0.0.0/0) from the ABR to reach external destinations.	Receives a default route (0.0.0.0/0) from the ABR to reach both external and inter-area destinations.
Type of LSAs Allowed	Allows Type-1, Type-2, and Type-3 LSAs. Type-5 LSAs are blocked.	Allows Type-1 and Type-2 LSAs. Blocks Type-3, Type-4, and Type-5 LSAs.
Configuration	`area <area-id> stub`	`area <area-id> stub no-summary`
Main Use Case	Useful when external routes are not needed in the area, but inter-area routes are required.	Useful for areas that need minimal routing information and rely on a single default route for all non-local destinations.
Traffic Optimization	Reduces external route advertisements, optimizing performance for areas with less interest in external destinations.	Maximizes simplicity and performance by drastically reducing routing information, suitable for edge areas with simple connectivity requirements.
Resource Savings	Moderate reduction in routing table size and CPU/memory usage.	Significant reduction in routing table size and CPU/memory usage.
Example Scenario	A branch office that requires access to other OSPF areas but not to external networks.	A remote office that connects only to a single central office and relies entirely on default routes.