What is a totally stubby area in OSPF?

Published by Charlie Davidson on

What is a totally stubby area in OSPF?

You can define totally stubby areas. Routers in totally stubby areas keep their LSDB-only information about routing within their area, plus the default route. Not-so-stubby areas (NSSAs) are an extension of OSPF stub areas.

What is totally not-so-stubby area in OSPF?

The OSPF not-so-stubby area (NSSA) feature is described by RFC 1587. and is first introduced in Cisco IOS® Software release 11.2. It is a non-proprietary extension of the existing stub area feature that allows the injection of external routes in a limited fashion into the stub area.

What is NSSA stubby totally stubby?

Basically NSSA and NSSA totally stubby are comparable to stub area and totally stubby area, respectively, with the exception of external route redistribution capabilities. NSSA will allow all Type 3 LSAs, while a totally stubby NSSA will have only one Type 3 LSA, i.e. the default route.

What is the difference between stub and totally stubby?

A stub area is an area in which advertisements of external routes are not allowed, reducing the size of the database. A totally stubby area (TSA) is a stub area in which summary link-state advertisement (type 3 LSAs) are not sent. A stub area disables advertisements of external routes.

What is Area 0 called in OSPF?

backbone area
The backbone area (Area 0) is the core of an OSPF network. All other areas are connected to it and all traffic between areas must traverse it. All routing between areas is distributed through the backbone area.

Why We Use Area in OSPF?

In OSPF, a single autonomous system (AS) can be divided into smaller groups called areas. This reduces the number of link-state advertisements (LSAs) and other OSPF overhead traffic sent on the network, and it reduces the size of the topology database that each router must maintain.

Why do we need AREA 0 in OSPF?

Albeit OSPF is a link state protocol, the way OSPF handles inter-area traffic leaves it prone to routing loops. This is why OSPF must connect back to area 0 – to avoid routing loops.

What is not-so-stubby area?

The OSPFv2 not-so-stubby area (NSSA) enables you to configure OSPFv2 areas that provide the benefits of stub areas, but that also are capable of importing external route information. The ASBR inside the NSSA imports external routes from BGP into the NSSA as type 7 LSAs, which the ASBR floods throughout the NSSA.

What type of LSAs are blocked in the totally stubby area?

A stub area that only allows routes internal to the area and restricts Type 3 LSAs from entering the stub area is often called a totally stubby area. You can convert area 0.0. 0.3 to a totally stubby area by configuring the ABR to only advertise and allow the default route to enter into the area.

What is Type 3 LSA?

The Summary (Type 3) LSA is used for advertising prefixes learned from the Type 1 and Type 2 LSAs into a different area. The Area Border Router (ABR) is the OSPF device that separates areas and it is this device that advertises the Type 3 LSA.

Why do we use AREA 0 in OSPF?

How does OSPF avoid loops?

Because inter-area OSPF is distance vector, it is vulnerable to routing loops. It avoids loops by mandating a loop-free inter-area topology, in which traffic from one area can only reach another area through area 0.

How to configure the totally stubby area in OSPF?

To configure Totally Stubby area, we have to add the “ no-summary ” command after the “ stub ” command. And, this should be done on the ABR only and not to the routers inside the Totally Stub area. Since my ABR is Anopheles router, I am going to do it here and Aedes stays with my previously configured “stub” command.

Which is the default route in totally stubby area?

From what I’m reading – Stub area, allows LSA 1 and 2 within the stub area and the ABR sends LSA 3 into the stub area. This LSA 3 is a default route – 0.0.0.0 /0 pointing to the ABR A Totally stubby area is the same, LSA 1 and 2, but instead of LSA 3 – ABR injects a default route of 0.0.0.0 /0 pointing to itself?

What’s the difference between OSPF stub and NSSA?

Stub area is isolated area that does not receive External LSA. Routers in Stub areas do not receive type 4 and type 5 LSAs it is replaced by a default route to external autonomous system advertised by the area border router (ABR) Stub area can have type 1, 2, and 3 OSPF LSAs.

What’s the difference between a stub and a totally stubby area?

I suggest that stub areas present more information (about networks and subnets outside the area and within the OSPF routing domain) while the totally stub area presents no information about any resource outside the area.

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