Cisco^® CCNP Routing Exam Notes : Scalable Networks, And Cisco Ios Features

The BSCI exam is of 75min duration and there will be approximately 65 questions. You need to score 690 or more to pass the exam. Visit the official website here

1. Scalable networks:

The key 5 characteristics of Scalable Internetworks are:

a. Reliable and available: An internetwork is usually up for 24 hours a day and seven days a week. b. Efficient: Efficiency means optimization of resources keeping in view available bandwidth. An internetwork should have less amount of overhead traffic, such as broadcasts, routing updates etc. c. Responsive: It is necessary that the internetwork meet QoS requirements for different protocols. Cisco IOS has been developed keeping in view the QoS demands. Different protocols may require different QoS standards. d. Adaptable: An internetwork should be able to accommodate variety of networks and protocols. The available protocols may include for example, TCP/IP, IPX, and SNA. An adaptable internet should be able to accommodate legacy as well as more recent technologies such as VOIP. e. Accessible and Secure: An internet should be accessible by using different access methods, such as dial-up, dedicated, switched connections. At the same time, it should provide secure environment.

2. The typical three-layer hierarchical internetworking model consists of the following:

a. Core layer: Core layer is responsible to provide an optimal and reliable transport structure. The core layer is the backbone network of the entire internetwork and may include LAN and WAN backbones. Core layer usually consists of fully redundant paths with technologies such as FDDI, Fast Ethernet, and/ or ATM. b. Distribution layer: Distribution layer is responsible to provide access to the internetwork as well as to the servers. Distribution layer sits between the Core layer and the Access layer. The policies such as ACLs are implemented at the distribution layer. Distribution layer is also known as workgroup layer. c.Access layer, provides the users, access to the resources on internetwork.

In real world, a single device may be functioning at both Access layer as well as distribution layer. This is true for even Core layer.

3. Network segmentation: Network congestion can be addressed by segmentation of the network. Network segmentation, also called micro segmentation, can be done by using:

a. Bridges, b. Routers, and c. Switches.

The primary purpose of segmentation is to reduce congestion in the network.

4. Bridges and switches forwards all broadcasts, which puts extra load on the network. In other words, though bridges divide the network into different collision domains, the broadcast domain remain only one. This increases the overhead on the network.

5. The Cisco IOS features that allow reduction in bandwidth are:

a. Access Control Lists: ACLs are used to permit or deny protocol update traffic, data traffic, and broadcast traffic. Cisco access lists are available for IP, IPX, and AppleTalk protocols. b. Snapshot routing: Snapshot routing can reduce WAN costs, by exchanging the routing table at predefined intervals. The routing tables for the distance vector protocols are kept frozen until the next update occurs. Snapshot routing is used only on distance vector protocols such as IP RIP. Snapshot routing is widely used on ISDN lines. c. Compression over WANs: Cisco IOS supports TCP/IP packet header, as well as data compression. Link compression is also supported, that compresses both header and data information in packets across point to point connections. d. DDR (Dial on Demand Routing): DDR are useful when the traffic flow is not continuous in nature. In DDR, channel is created only after intended traffic is detected by the router, by dialing the destination. e. Switched network access: Switched networks, such as Frame Relay, X.25 can share the bandwidth by establishing virtual circuits. f. Optimization of routing table size: Routing table entries consume bandwidth and processing power. These entries can be reduced by techniques such as route summarization, and incremental updates.

6. Snapshot routing builds routing table based on a snapshot of a dynamic routing table available when the network is active. The snapshot routing table is used until another activity occurs on the network, at which time the routing table is rebuilt. No routing information is exchanged when the network is quiet. Snapshot routing can be applied to distance vector protocols such as IP RIP, IGRP, IPX RIP, and RTMP.

7. Cisco IOS supports the following queuing methods:

a. Weighted fair-queuing: This is an automatic queuing method that provides fair bandwidth to all network traffic. b. Priority queuing: Here, one particular type of traffic is given priority over all other types of traffic. Thus this particular traffic, for which priority is given, is assured of bandwidth. All other types of traffic do not have assured bandwidth. c. Custom queuing: Here, each traffic type gets a pre-allocated bandwidth. Certain types of traffic can be allocated higher bandwidth depending on the requirement.

8. RIP

a.IP (and IGRP) always summarizes routing information by major network numbers. This is called classful routing. b. IP RIP based networks send the complete routing table during update. The default update interval is 30 seconds. c. RIP version 2 is a classless routing protocol, where as RIP version 1 (RIP 1) is a classful routing protocol. The disadvantage of classfull routing is that some address space may be wasted. In classless routing, routing protocols exchange the subnet mask information during periodic routing updates. This allows variable subnet masks to be used in the network, allowing better use of address space. For example, a WAN link may need only two IP addresses. If you use classless routing protocol with, say 6 bits for subnetting (62-2 subnets), only 2 subnet addresses are utilized and the remaining become wasted. On the other hand, if you use classless routing protocol, Variable Length Subnet Mask (VLSM) can be used within the network, giving only 2 valid addresses for the WAN link, thus saving valuable address space. (If you are using IP addresses, address space involves IP addresses).

9. Metric limit for link-state protocols is 65,533.

10. Convergence is the term used to describe the state at which all the internetworking devices, running specific routing protocol, are having the same information about the internetwork in their routing tables. The time it takes to arrive at common view of the internetwork is called Convergence Time.

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