Cisco® CCDA Exam Notes : Distribution Layer Responsibilities, Hsrp, Cdp, And Network Management.

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11. Distribution layer lies in between the Core layer and Access layer. It usually deals with the following:

  • Security
  • Access Control Lists
  • Route Summarization
  • Media translation

12. Some important port numbers to know:

  • HTTP uses port number 80.
  • FTP uses port number 21
  • SMTP uses port number 25
  • Telnet uses port number 23
  • TFTP uses port number 69

13. Hot Standby Router Protocol (HSRP) is used for selecting a standby router when one router fails. That is, HSRP allows IP workstations to continue uninterrupted communication over the internetwork even if their default router becomes unavailable.

14. The number of router hops from one edge to another edge in a network is called diameter. Limiting the diameter of an internetwork provides predictable and consistent performance and ease of troubleshooting. The network diameter is more appropriate at Core layer.

15. Cisco Discovery Protocol (CDP) is a proprietary protocol supported by Cisco devices and gives information about the devices. Used for automatic discovery of Cisco networking components in a network.

16. Widely used network management tools from Cisco are:

  • Cisco Works
  • Cisco View
  • Netsys Connectivity Service Manager
  • Netsys Performance Service Manager
  • Cisco FastStep
  • Cisco Works 2000

17. ISO defines five types of network management processes. These are (remembered as FCAPS):

1. Fault Management : This is a vital function of a network management system. Fault management consists of fault detection, correction, and verification checks on a fault. Since any fault directly impacts the quality of service, automatic fault detection and correction need to be implemented where possible. In addition, fault management should include virus prevention, and regular backups.

2. Configuration Management : Configuration management facilitates management of hardware and software resources more efficiently. In a large computer network, there can be several versions of software and hardware resources giving rise to difficulty in troubleshooting and/or upgrading the systems. The database is made easily accessible to attend to maintenance/ up gradation procedures in a timely and efficient manner.

3. Accounting Management : This function helps in fair use of resources. For example, network bandwidth utilization by individual groups can be measured and appropriate quotas can be assigned depending on the requirement and fair usage. It also enables billing based on the resource usage.

4. Performance Management : This includes collecting the network parameters of interest, such as bandwidth utilization, packet errors, retransmissions etc. A baseline is established during normal traffic flow. Performance threshold are established, against which the measured parameter values are compared for acceptable network performance. If any non-compliance is determined, the network management station is alerted by visual, audio, logger, and/or by email alerts.

5. Security Management : Security management refers to the control of access to the network resources. The internal network resources should be made available only to authorized users or systems as per the given criteria. All attempts to access the resources without appropriate authorization to a given resource need to be logged or an alarm may be given, depending on the requirement. There can be different levels of access, depending on the user type, such as internal or external. Also, if the corporate network is participating in Internet or extranet, added levels of security are required.

18. Frame Relay:

  • Frame Relay is well suited for intermittent and burst traffic.
  • Frame Relay can carry multiple PVCs over a single physical circuit.
  • CIR (Committed Information Rate) is the rate at which a Frame Relay network agrees (guaranteed) to transfer information under normal conditions, averaged over a minimum increment of time. Expressed in bits/ Sec. Any packets traveling over the CIR are subject to be discarded under certain conditions.
  • Frame Relay uses Data Link Connection Identifier (DLCI) to identify Layer 2 connections in a Frame Relay network.
  • Bc stands for Committed Burst. This is a negotiated tariff metric in FR network.
  • Cisco supports the use of a 10-bit DLCI field resulting in a maximum of 1024 data link connection identifiers with numbering starting at 0 and ending at 1023.

20. The catalyst 1900 series switches are equipped with 12 (1912) or 24 (1924) switched 10BaseT ports. These ports can be attached to hosts or hubs. These switches also have two 100BaseT ports. These high-speed ports can be used for attachment to Servers and backbones.

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