OSPF Areas

Why more than one Area is used in an OSPF network?

there are multiple reasons, like following
*to reduce the LSA flood (Exchange of routing table)
*You can divide your network in to multiple area (example every campus will be the part of different area and the main campus become the area 0 means backbone area)
*You can configure the failover
*if one area occur the problem, it will not effect other areas

and many other reasons.

HiHi,

OSPF (Open Shortest Path First) is an Interior Gateway Protocol (IGP) that is used to decide routing within a single Autonomous System (AS).

It is a kind of implementation of link status routing protocol, which belongs to the Interior Gateway Protocol (IGP) and operates in an autonomous system.

OSPF supports load balancing, service type-based routing, and multiple routing forms, such as specific host routing and subnet routing.

NGAF devices enable and set OSPF dynamic routing protocol, including network configuration, interface configuration, parameter configuration, information display, debugging options, etc.

You can locate the detailed settings in the NGAF V8.0.47 User Manual.

Regards,

Multiple OSPF (Open Shortest Path First) areas are used in OSPF networks for several reasons:

Scalability: OSPF is designed to support large and complex networks. By dividing the network into multiple areas, each area can have its own link-state database and routing tables. This hierarchical structure reduces the size of the link-state database and the amount of routing information each router needs to process, making the network more scalable.

Reduced SPF Calculations: OSPF routers within an area only need to perform SPF (Shortest Path First) calculations based on the link-state information within their own area. This reduces the computational overhead compared to calculating routes for the entire OSPF domain, which would be the case in a single area network.

Controlled Routing Information: OSPF areas provide a boundary for the exchange of routing information. Routers within an area have detailed knowledge of the topology within that area but only summary information about other areas. This containment of routing information improves network stability and control.

Improved Convergence: When there is a change in the network topology, OSPF routers in an affected area can quickly converge by recalculating routes within their area without affecting routers in other areas. This localized recalculation reduces the impact of network changes on the entire OSPF domain.

Security and Policy Segmentation: Different areas can be used to implement security policies or route summarization. For example, you can isolate sensitive parts of the network in one area and apply access control lists (ACLs) or firewall rules more easily.

Redundancy and Fault Isolation: Multiple areas allow for greater redundancy and fault isolation. If there is a failure or congestion in one area, it is less likely to impact routers and traffic in other areas. This helps maintain network availability.

Administrative Boundaries: OSPF areas can also align with administrative boundaries within an organization. Different departments or geographical locations can be assigned to separate areas to reflect the organization's structure.

In summary, using more than one OSPF area in a network improves scalability, reduces routing overhead, enhances network stability, and provides flexibility for implementing security and policy controls. It allows network administrators to design OSPF networks that meet the specific requirements and constraints of their organization.

Using multiple OSPF (Open Shortest Path First) areas in a network offers several benefits:

Reduced LSA Propagation:

OSPF uses Link State Advertisements (LSAs) to exchange routing information. In a large OSPF network with a single area, every router needs to process LSAs from every other router. With multiple areas, LSAs are contained within their respective areas, reducing the amount of LSA processing overhead.
Reduced Link-State Database (LSDB) Size:

In a single OSPF area, all routers maintain a complete LSDB. As the network grows, the LSDB can become large and memory-intensive. Multiple areas allow each router to maintain a smaller LSDB containing only the information for its area.
Faster Convergence:

Smaller LSDBs and reduced LSA propagation result in faster OSPF convergence times. This means that the network can adapt more quickly to changes in the network topology.
Improved Scalability:

Large OSPF networks can be difficult to manage and can strain router resources. By dividing the network into areas, you can effectively compartmentalize the network, making it more manageable.
Isolation of Network Instabilities:

If there is a problem or instability in one area (like a network loop or a high rate of topology changes), it's less likely to impact routers in other areas. This isolation helps to contain issues and prevent them from spreading across the entire network.
Control over Summarization:

OSPF allows for route summarization at area boundaries. This can help to reduce the size of routing tables and control the propagation of routes between areas.
Hierarchical Network Design:

Multiple areas facilitate a hierarchical network design, which can be easier to manage and troubleshoot. It also allows for better route summarization and control over traffic flows.
Reduced SPF Tree Calculation:

With fewer routers participating in SPF tree calculations due to smaller LSDBs, the CPU and memory resources required for these calculations are reduced.
Improved Network Security:

Different areas can have different security policies, allowing for more granular control over access and routing.
It's important to note that the decision to use multiple OSPF areas should be based on the specific requirements and characteristics of the network. While multiple areas offer benefits, they also introduce additional complexity in terms of design, configuration, and troubleshooting. Therefore, the network design should be carefully planned to ensure it aligns with the organization's goals and requirements.

There are some key reasons of multiple areas in OSPF network:

Scalability: OSPF networks with large numbers of routers can become difficult to scale and manage. Dividing the network into multiple areas can help to reduce the complexity of the network and make it easier to manage.

Performance: Routing updates in OSPF networks can be bandwidth-intensive. By dividing the network into areas, routers only need to exchange routing information with other routers in the same area. This can help to reduce the amount of bandwidth used for routing updates and improve the overall performance of the network.

Security: Dividing the network into areas can help to improve security by isolating different parts of the network from each other. This can make it more difficult for attackers to gain access to the entire network.

Reliability: If a problem occurs in one area of an OSPF network, it is less likely to affect other areas. This can help to improve the overall reliability of the network.

OSPF, or Open Shortest Path First, is a routing protocol that is used to distribute routing information within a single autonomous system (AS) in a network. One of the key features of OSPF is its ability to divide the network into multiple areas. This allows for more efficient and scalable routing, as well as improved network security and stability. Each OSPF area is a separate routing domain, with its own unique routing table. This allows for more efficient use of network resources, as well as reducing the size of the overall routing table.

Additionally, OSPF areas can be used to separate different parts of the network, such as different departments or locations, providing a degree of isolation and security. It's also possible to connect different areas together using a backbone area, which allows for communication between the different areas. This allows for a more efficient routing of traffic throughout the entire network, while still maintaining the benefits of separating the network into multiple areas. Overall, OSPF's use of multiple areas provides a powerful and flexible way to organize and manage large and complex networks.

Question 4:OSPF Areas?

Answer:

BackBone Area:

The backbone area is area 0. It plays the role of the central node in the OSPF network and the link information of other areas is transmitted through area 0. so generally OSPF area consists of all networks in area ID 0.0.0.0 which are attached to the routing devices.
Standard Area:

In this type of area, OSPF packets can be normally transmitted and they can support up to 1,2,3,4, and 5 LSAs(Link State Advertisements). Ensure optimal routing since all routers know about all routes
Stub Area:

As the name defines this type of area does not accept external routes and does not accept the link information of the other routers outside the area. these areas do not receive type 4 or 5 LSAs from their ABRs(Area Border Router).
Totally stubby area:

These are completely stub areas same as sub-area this type of area does not accept external routes and does not accept the link information of the other routers outside the area. It should be noted here that since the default route is sent using Type 3 LSAs, the complete stub area does not allow ordinary Type 3 LSA packets, but it supports this type of LSA with default routes. This area supports Type 1, Type 2 LSAs, and Type 3 LSAs with default routes.
Not so Stubby area:  

It also has to send external routes to other areas. This area supports 1, 2, 3, and 7 LSAs. An NSSA makes use of type 7 LSAs.The functionality of NSSA is to designate a normal (stub) NSSA, all routers in the area must be so configured: This allows an ASBR to advertise external links to an ABR, which converts the type 7 LSAs into type 5 before flooding them to the rest of the OSPF domain.

Multiple areas are used in an OSPF (Open Shortest Path First) network to improve scalability, reduce routing overhead, and enhance network performance. Using multiple areas in an OSPF network provides benefits such as reduced LSA flooding, faster convergence, enhanced scalability, easy summarization, and improved security and fault isolation.

There are several reasons why more than one area is used in an OSPF network:

To improve performance. In some cases, dividing the network into areas can improve performance by reducing the amount of routing traffic that is generated. This is because OSPF routers only need to exchange routing information with routers in their own area.

To improve security. By dividing the network into areas, it is possible to restrict the flow of routing information between areas. This can help to improve security by preventing unauthorized access to routing information.

To isolate critical networks. For example, a company might choose to use a separate OSPF area for its critical production networks. This would help to protect the production networks from routing problems that might occur in other parts of the network.

To reduce the size of the link-state database (LSDB). Each OSPF router maintains a copy of the LSDB for its area. By dividing the network into areas, each router only needs to maintain a copy of the LSDB for its own area. This can significantly reduce the memory and CPU requirements on each router, especially in large networks.

To separate different departments or business units. For example, a large company with multiple departments might choose to use a separate OSPF area for each department. This would allow each department to have its own routing policy and would also help to improve security.