How is area defined in OSPF?
By definition an OSPF area is a collection of networks, not a collection of routers. A backbone network segment is an IP subnet that belongs to the area identified by 0.0. 0.0. Areas that are not physically connected to the backbone are logically connected by a backbone ABR using an OSPF virtual link.
What is stub area network?
A stub network, or pocket network, is a somewhat casual term describing a computer network, or part of an internetwork, with no knowledge of other networks, that will typically send much or all of its non-local traffic out via a single path, with the network aware only of a default route to non-local destinations.
What is stub autonomous system?
A stub autonomous system is an AS that is connected to only one other AS. Service from an ISP is an example of this (or a lower-tier ISP that gets its service from another ISP). A transit autonomous system is one that offers the ability to route data from one AS to another AS.
What are the main features of OSPF?
OSPF supports/provides/advantages –
- Both IPv4 and IPv6 routed protocols.
- Load balancing with equal-cost routes for the same destination.
- VLSM and route summarization.
- Unlimited hop counts.
- Trigger updates for fast convergence.
- A loop-free topology using SPF algorithm.
- Run-on most routers.
- Classless protocol.
What is stub network in OSPF?
A stub network is a network that contains only a single router – its gateway to the rest of the topology. Typically, all Ethernet interfaces where only end stations are connected are considered as stub networks by OSPF.
What is the purpose of a stub area?
A stub area disables advertisements of external routes. By default, the ABR sends summary LSAs (type 3 LSAs) into stub areas. You can further reduce the number of LSAs sent into a stub area by configuring the device to stop sending type 3 LSAs into the area.
What is stub area flag in OSPF?
Stub area flag: Two routers have to also agree on the stub area flag in the Hello packets in order to become neighbors. OSPF allows certain areas to be configured as stub areas. External networks, such as those redistributed from other protocols into OSPF, are not allowed to be flooded into a stub area.
What is stub router in OSPF?
The OSPF Stub Router Advertisement feature allows you to bring a new router into a network without immediately routing traffic through the new router and allows you to gracefully shut down or reload a router without dropping packets that are destined for other networks.
What area in OSPF is considered AS backbone?
An OSPF backbone area consists of all networks in area ID 0.0. 0.0, their attached routing devices, and all ABRs. The backbone itself does not have any ABRs. The backbone distributes routing information between areas.
What is the purpose of OSPF?
Routers connect networks using the Internet Protocol (IP), and OSPF (Open Shortest Path First) is a router protocol used to find the best path for packets as they pass through a set of connected networks.
What is stub area in router?
What is the difference between backbone area and stub area in OSPF?
The backbone is considered a standard area. Stub areas can contain type 1, 2, and 3 LSAs. A default route is substituted for external routes. Totally stubby areas can only contain type 1 and 2 LSAs, and a single type 3 LSA.
What is a stub network in OSPF?
What is Area 0 called in OSPF?
Backbone Area
Backbone Area This is the central area in your OSPF routing domain which all areas must connect to. This area is labeled area 0 (or the longhand version 0.0. 0.0).
What layer is OSPF?
OSPF and BGP belong to the Application Layer.
What is the main importance of stub network?
Non-local stub network traffic uses a single logical path when traveling in and out of the network. Stub networks are essentially local area networks (LAN) that either do not connect to the outside and relay data packets internally or are dead-end LANs that know of only one network exit.
What is a stub area in OSPF?
In the middle you’ll find the backbone area and the other areas are configured as the different stub area types. If you configure an area as stub it will block all type 5 external LSAs. All the prefixes that you redistributed into OSPF from another routing protocol are not welcome in the stub area.
What is the default behaviour of OSPF prefixes?
What we’ve learned here is that the default behaviour in OSPF is to take all prefixes from one area, and advertise them to another area. The border router between Area 0 and Area 2 takes all the prefixes in Area 2, and redistributes them into the backbone.
What are the rules of OSPF?
Each OSPF network that is divided into different areas must follow these rules: A backbone area —which combines a set of independent areas into a single domain—must exist. The backbone area must not be partitioned—divided into smaller pieces—under any failure conditions, such as link or router down events.
What are the different OSPF LSA types?
Make sure you understand the different OSPF LSA types before you continue reading or it might be difficult to follow me. Let me start by summing up the special area types: Stub area. Totally stub area. NSSA (not so stubby area) Totally NSSA (totally not so stubby area)