Chapter 3 Configuring Open Shortest Path First

OSPF Overview

Area Border Routers

ABRs have multiple interfaces that connect directly to networks in two or more areas. An ABR runs a separate copy of the OSPF algorithm and maintains separate routing data for each area that is connected to it, including the backbone area.

ABRs also send configuration summaries for their attached areas to the backbone area, which distributes this information to other OSPF areas in the autonomous system. In Figure 3-1, there are two ABRs. ABR 1 interfaces area 1.1.1.1 to the backbone area. ABR 2 interfaces the backbone area to area 1.1.1.2, a stub area.

Note ABRs are always backbone routers. You must configure ABRs to the backbone area.

Stub Area

A stub area is an area that does not accept or distribute detailed network information external to the area. A stub area has only one router that interfaces the area to the rest of the AS. The ABR attached to the stub area advertises a single default external route into the area. Routers within a stub area use this route for destinations outside the autonomous system, as well as for inter-area routes. This relationship conserves LSA database space that would otherwise be used to store external LSAs flooded into the area. As shown in Figure 3-1, area 1.1.1.2 is a stub area that is reached only through ABR 2.

Autonomous System Boundary Routers

ASBRs provide connectivity from one autonomous system to another system. ASBRs exchange their autonomous system routing information with boundary routers in other autonomous systems. Every router inside an autonomous system knows how to reach the boundary routers for its autonomous system.

ASBRs can import external routing information from other protocols like RIP and redistribute them as AS-external LSAs to the OSPF network. If the CSS is an ASBR, you can configure it to advertise VIP addresses for content as AS external routes. In this way, ASBRs flood information about external networks to routers within the OSPF network.

 

 

Cisco Content Services Switch Routing and Bridging Configuration Guide

 

 

 

 

 

 

OL-8241-02

 

 

3-5

 

 

 

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Cisco Systems OL-8241-02 manual Area Border Routers, Stub Area, Autonomous System Boundary Routers
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OL-8241-02 specifications

Cisco Systems OL-8241-02 is a significant component of Cisco's extensive portfolio, catering specifically to the needs of enterprise-level networking. This module is designed to provide advanced routing capabilities, aiding organizations in achieving robust connectivity and efficient data transmission across their networks. It is particularly popular among businesses that require reliable performance and scalability.

One of the main features of the OL-8241-02 module is its support for multiple protocols, including OSPF, EIGRP, and BGP, which allows for seamless integration into various network configurations. This flexibility ensures that organizations can adapt to evolving networking demands without undergoing complete infrastructure overhauls. Furthermore, the module includes advanced security features, such as IPsec VPN support and integrated firewall capabilities, enhancing overall network security and protecting sensitive data from potential threats.

Another noteworthy characteristic of the OL-8241-02 is its exceptional performance metrics. With high throughput rates and low latency, the module can handle significant amounts of data traffic without compromising on speed. This efficiency is particularly critical for businesses that rely heavily on real-time data applications, such as video conferencing and online collaboration tools.

The OL-8241-02 also incorporates cutting-edge technologies like Quality of Service (QoS), which prioritizes network traffic based on application requirements. This feature is essential for ensuring that critical applications receive the bandwidth they need, while less critical tasks can be deprioritized during peak usage times. Additionally, the module supports IPv6, which is vital for organizations looking to future-proof their network infrastructure amid the global transition from IPv4.

The ease of management is another highlight of the OL-8241-02, with user-friendly interfaces and compatibility with Cisco's robust management software. This capability allows IT teams to monitor performance metrics, troubleshoot issues, and configure settings with minimal complexity.

In summary, the Cisco Systems OL-8241-02 module stands out for its versatility, performance, and security features. Equipped with the ability to support various protocols, advanced security measures, and efficient traffic management, it proves to be a reliable choice for enterprises aiming to enhance their networking capabilities and ensure seamless operational continuity.
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