Exam notes for CCDA Exam

Cisco Certified Design Associate

(Exam Code: 640-864)

The CCDA certification is a foundation exam for testing Cisco network design fundamentals for the small office/home office (SOHO) market. CCDA certified professionals will be able to design simple routed and switched networks involving LAN, WAN, and dial up access for small businesses. The exam is of 2 hours duration and there will be approximately 65 questions. Many questions are scenario based. Click here to visit official Cisco website to know more about this certification. CCDA is a pre-requisite for CCDP (Cisco Certified Design Professional) certification offered by Cisco Systems.

1. When designing a network, document the application characteristics. This should include present and future applications. Following are some important characteristics that need to be documented.

• Application name

• Application type: Browser (HTTP), e-mail, database etc.

• Protocols - IP, IPX, SNA, AppleTalk etc.

• Number of users

• Number of hosts

2. Ethernet, Token Ring, and Fiber Optic:

• Token ring frame doesn't have a preamble, whereas Ethernet frame has 7/8 bytes preamble for each frame transmitted. A Token Ring frame starts with an SD (Starting Delimiter) of size 1 byte. FDDI frame have a preamble of 8 bytes (64 bits).

• Maximum size of collision domains for 100BaseFX multimode fiber is 412 meters in half duplex and 2000m if full duplex is used.

• Loop back and collision detection should be disabled when you are running full duplex Ethernet.

• The Routing Information Field (RIF) of a Token Ring frame contains the Route Descriptor. The route descriptor in turn contains the Ring Number and Bridge Number.

• In Source Route Bridging (SRB), the source node finds the routes to the destinations on a network using explorer frames. This is different from Ethernet transparent bridging; the bridges build and maintain tables (MAC tables) containing paths to destinations.

• Source Route Transparent bridging (SRT) enables a bridge to function as both a source-routing bridge and a transparent bridge.

• In Token Ring network, when an explorer frame arrive at the destination, the destination node sets the D - bit (Direction bit) to 1 and sends the frame back to the source node, indicating successful route discovery.

• There are four different Ethernet framing types. Although several encapsulation types can share the same interface, clients and servers with different types cannot communicate without a router.

  • Ethernet_802.3 - The default for NetWare versions 2.x through 3.11. This is also the default for Cisco routers. Cisco refers to this as Novell-ether.

  • Ethernet_802.2 - The default for NetWare 3.12 and later versions. Cisco refers to this as SAP.

  • Ethernet_II - This is also used with TCP/IP and DECnet. Cisco refers to this as ARPA.

  • Ethernet_SNAP - This is also used with TCP/IP and AppleTalk. Cisco refers to this as SNAP.

• The specification 802.3z describes gigabit Ethernet over fiber or shielded copper.

• The specification 802.3ab (1000BaseT) describes gigabit Ethernet over Category 5 UTP.

3. Traffic pattern:

• Terminal / Host: Applications based on Terminal / Host are low - volume character traffic. The traffic from the terminal will be a few characters while the Host returns screen full of characters.

• Client / Server: The traffic flow in Client / server environment is bi-directional and asymmetric. Traffic sent to the host is usually less than 100 bytes and the return traffic from the host can be more than 1500 bytes. HTTP, FTP are examples of Client / Server Protocols.

• Peer/ Peer: In peer-to-peer environment, traffic flow is bi-directional and symmetric. Peer to peer communication is commonly used in work groups.

4. Routing protocols:

• RIP is useful for small networks.

• OSPF is a standards based, scalable protocol.

• IGRP and EIGRP are Cisco proprietary routing protocols. EIGRP is preferred when there are multiple routed protocols such as IP, IPX etc. Cisco's IGRP and EIGRP can load balance traffic across multiple routes that have unequal metrics by using "variance" command.

• Category	Routing Protocol
  a. Classless/ VLSM support	EIGRP, OSPF, ISIS, RIP v2, BGP
  b. Classful / No VLSM	RIP v1, IGRP

• Category	Routing Protocol
  a. Distance Vector	IP RIP, IPX RIP, IGRP, RTMP
  b. Link - State	OSPF, NLSP, ISIS
  c. Hybrid	EIGRP

• NLSP (Netware Link Services Protocol) is a Link State Routing Protocol, and supports hierarchical routing with area, domain, and global internetwork components. Group of networks form an area. A group of areas form a domain. A group of domains form a global internetwork. Novell NetWare networks have three options for routing:

  • IPX RIP

  • NetWare Link Services Protocol (NLSP)

  • Enhanced IGRP for IPX

• APPN stands for Advanced Peer-to-Peer Networking. IBM introduced APPN to overcome the limitations of traditional Systems Network Architecture (SNA).

• IP RIP based networks send the complete routing table during update. The default update interval is 30 seconds. Major distance vector protocol Update timers are as below:

• Routing protocol Default update time (Sec)

  • IP RIP : 30

  • IP IGRP: 90

  • RTMP : 10

  • IPX RIP : 60

• 10. AppleTalk networks have three possible routing protocols:

  • Routing Table Maintenance Protocol (RTMP)

  • Apple Talk Update - Based Routing Protocol (AURP)

  • Enhanced IGRP for Apple Talk

• Of these, RTMP is the most commonly used routing protocol

• 11. IGRP, EIGRP metrics:

  • Bandwidth: This is represents the maximum throughput of a link.

  • MTU (Maximum Transmission Unit): This is the maximum message length that is acceptable to all links on the path. The larger MTU means faster transmission of packets.

  • Reliability: This is a measurement of reliability of a network link. It is assigned by the administrator or can be calculated by using protocol statistics.

  • Delay: This is affected by the bandwidth and queuing delay.

  • Load: Load is based among many things, CPU usage, packets processed per sec.

5. IP, IPX are examples of routed protocols. RIP, EIGRP are examples of routing protocols.

6. Identifying information and traffic flows is part of characterizing the customer's application. The following fields can help identify the traffic flows:

• Application: Identify the applications that run on your customer's network

• Application type: Categorize the application as a database, groupware, Web etc.

• Number of Servers, hosts, and users: Note the number of servers, hosts, and users using the specified application.

• Segments: Locate the segments that the application flows.

7. Hierarchical layer model:

• Core layer: Designed for high availability and redundancy. Core layer is the high-speed switching backbone of any network. The core layer has the following characteristics:

  • High reliability

  • Adapt to changes quickly

  • Lower latency

• Distribution layer: Address summarization and media translation are applied in the distribution layer. Distribution layer lies in between the Core layer and Access layer. It usually addresses the following:

  • Security

  • Access Control Lists

  • Route Summarization

  • Media translation

• Access layer: The access layer consists of the remote office sites using ISDN, Frame Relay etc. Local area networks segments are also part of the access layer.

8. Cisco ConfigMaker is used for configuring networks using Cisco Switches and Cisco routers. At present, ConfigMaker can't support some high-end devices like 7000 series routers. It can be used to configure small networks of Cisco routers (800, 1000, 1600, 1700, 2500, 2600, 3600, and 4000 series), 1500 series switches, and Hubs from a single PC.

9. CiscoWorks is a suite of integrated network management tools that will help an administrator in maintenance of small to medium sized business networks.

Cisco View is a GUI based device management software application that provides dynamic status, statistics, and configuration information. Cisco View graphically displays a real time physical view of Cisco devices.

TACAC+ (Terminal Access Controller Access Control System +): provides complete network access security (NAS) for dial-in connections.

10. Configuration management refers to base lining, modifying, and tracking configuration changes of network devices.

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 a significant parameter 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):

• 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.

• 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.

• 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.

• 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.

• 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.

21. ISDN: The ISDN Primary Rate Interface (PRI, also known as 23B+D1) service delivers 23 B channels and one 64KBPS D channel for a total bit rate of up to 1.544 MBPS.

ISDN BRI will have 2B + 1D channels, the total bandwidth is 64X2 +16 = 144 KBPS

22. The most important design rule for 100MBPS Ethernet is that the round trip collision delay must not exceed 512 bit times, which is same as that of 10BaseT. However, a bit time in 100BaseT is 10 times smaller. Therefore, a bit time on a 100 MBPS Ethernet is 0.01 microseconds, compared to 0.1 microseconds on a 10 MBPS Ethernet. Therefore, the maximum round trip delay for a 100 MBPS Ethernet is 5.12 microseconds whereas that of 10BaseT is 51.2 microseconds.

23. Cisco switches support the following trunking protocols:

• ISL (Inter Switch Link) and

• 802.1q

24. Class I repeaters have a latency of 0.7 microseconds and only one repeater hop is allowed.

Class II repeaters have a latency of 0.46 microseconds and one or two repeater hops are allowed.

25. Cisco Routers:

• 1600 series access routers: These are inexpensive, easy to use, multiprotocol routers. Cisco 1600, and 2600 series routers have optional expansion modules.

• The 4000 series routers have the following features:

  • High-density LAN connectivity

  • Medium-density WAN and dial up connectivity: Up to 16 ISDN BRI / 32 sync/ async serial ports or combination

  • FDDI / IBM internetworking connectivity

26. CiscoView can be integrated with several other network management platforms like HP OpenView, IBM NetView, CiscoWorks etc. to provide a better system to manage Cisco devices.

27. Route summarization reduces the route distribution and route-processing overhead in a network.

28. The HSSI interface on a Cisco router can support speeds up to 52 MBPS.

29. Catalyst switches:

• Catalyst 1800 is a Token Ring switch that has 16 dedicated or shared ports in the base unit plus two feature -card slots.

• Catalyst 2900 Fast Ethernet switch is a 14 port, fixed configuration, fast Ethernet switch. Catalyst 1900 Ethernet switch features 25 switched Ethernet ports providing attachment to individual workstations and 10BaseT hubs. It also has two 100BaseT ports for high-speed connectivity to servers and backbones.

• The catalyst 2820 Ethernet switch has 25 switched Ethernet ports and two high-speed expansion slots.

30. Bandwidths (typical):

• Dial up: up to 56 KBPS

• ISDN BRI: up to 2 numbers of 64 KBPS B channels and 16 KBPS D channels

• T1: 1.544 MBPS

• E1: 2.048 MBPS

• DS3: 44.736 MBPS

31. The use of traffic shaping limit the congestion due to surges in network traffic. Traffic shaping is used in ATM, Frame Relay, and other types of networks.

32. IGMP (Internet Group Management Protocol) is a protocol used by IP hosts to report their multicast group memberships to an adjacent multicast router.

33. LAN related protocols:

• IEEE 802.5 in IEEE LAN protocol that uses token passing access at 4 or 16 MBPS over STP cabling and is similar to IBM Token Ring.

• 802.3 uses CSMA/CD.

• 802.1 describes an algorithm that prevents bridging loops by creating a spanning tree.

34. HDLC: Each vendor’s implementation of HDLC is unique. Cisco's HDLC uses proprietary, default encapsulation. When you are using a Cisco router with a non-Cisco router, it is recommended to use PPP or any standards based encapsulation.

35. DNS, WINS, DHCP:

• DNS is used for resolving domain names to IP addresses

• DHCP is used for dynamic assignment of IP addresses

• WINS is used for resolving NetBIOS names to IP address

36. FragmentFree switching, as the name indicates, looks for any bus activity before forwarding a frame for any possible collisions. This collision in Ethernet happens during the first 64 bytes. Therefore, the switch waits for 64 bytes time before forwarding a frame.

37. Capacity and delays:

• At 70% utilization, a WAN link is considered running at full capacity.

• At 40% utilization, an Ethernet link is considered running at full capacity.

• At 80% utilization, a Token Ring network is considered running at full capacity.

• 100ms or less should be the response time when a network is considered working satisfactorily.

• The allowable delay for Class II repeater is only 92 bit times. The allowable delay for a class I repeater is 140 bit times.

38. VTP is a Layer 2 messaging protocol. It carries configuration information throughout a single domain. VTP operates in one of three modes:

• Server mode

• Client mode

• Transparent mode

VTP Servers can create, modify, or delete VLANs and other configuration parameters for the specified VLAN domain.

A VTP client can't create, change, or delete VLANs.

A VTP transparent mode is used when a switch is not required to participate in VTP, but only pass the information to other switches. Transparent switches don't work either as Server or clients.

Configurations made to a single switch, called VTP server, are propagated across the switch fabric under a single domain control. Other switches, configured as VTP clients, learn the configuration information from the server.

39. TCP is a full-duplex, connection-oriented protocol. It incorporates error checking as well.

UDP (User Datagram Protocol): UDP is a thin protocol. UDP is a connectionless protocol. It doesn't contact the destination before sending the packet and doesn't care whether the packet is reached at the destination. UDP uses port number 6.

The port number used by TCP is 6 and that of UDP is 17.

40. Cisco uses TFTP protocol to distribute IOS over a WAN link.

41. It is important to know the difference between a collision domain and a broadcast domain. When you use Hubs, all the nodes connected to the hub will be in the same collision domain. However, when you use switches and implement VLANs, each VLAN will be in a separate broadcast domain. The packet forwarding between VLANs is achieved through the use of routing.

42. IP routing protocols can load balance across up to six equal cost parallel links. The "maximum-paths" command can be used to change the number of links that the router will have to load-balance over IP.

42. Practice your demonstration before final demonstration to the customer.

43. Access Lists:

• IP access list should be created with the ACCESS-LIST command. After the list is created, it can be applied to an interface with the IP ACCESS-GROUP command.

• When applying access-lists, on a given interface, there can be only one access list per protocol for inbound. Similarly, there can be only one access list per protocol for outbound.

• An example to remove an access list from an interface:

  • Int s0

  • No access-group 10

44. Spanning Tree Protocol (STP) 802.1d is used to prevent routing loops. In Cisco Catalyst 5000 series switches, use BDPUs (Bridge Protocol Data Units) to determine the spanning tree topology. STP uses a Tree Algorithm (STA) to prevent loops, resulting in a stable network topology.

45. IPX address consists of 32-bit network address and 48-bit host address. The network portion of the address is configured by the administrator. The host part of the address is the 48-bit MAC address on the network interface card of the node.

46. ISL, 802.1Q are the VLAN trunking protocols associated with Fast Ethernet. The VLAN trunking protocol defined by 802.10 is associated with FDDI. LANE (LAN Emulation) is associated with ATM.

47. Compression algorithms supported by Cisco IOS are:

• HDLC - STAC;

• LAPB - STAC, Predictor;

• PPP - STAC, Predictor, MPPC

• Frame-Relay - STAC, FRF.9

PPP is supported by STAC, Predictor, and MPPC. Compression algorithms supported by Frame-Relay for payload compression are STAC, and FRF.9.

48. Data Link Switching (DLSw) was introduced by IBM to overcome the limitations of SRB networks. The Cisco implementation of DLSw is called DLSw+. Benefits of DLSW+ are over SRB are:

• Link layer acknowledgements and keep-alive messages of SNA do not have to travel over WAN link,

• DLSw+ traffic can be rerouted in case of link failures

• rioritization of traffic over WAN links

49. The permitted numbers for some important access-lists are:

• 1-99: IP standard access list

• 100-199 :IP extended access list

• 600-699: AppleTalk Access list

• 800-899 : IPX standard access list

• 900-999 : IPX extended access list

• 1000-1099: IPX SAP access list

• 1100-1199: Extended 48-bit MAC address access list

The format for standard IPX access list is:

access-list {number} {permit/ deny} {source} {destination}

50. By giving the command "show ip route igrp", we ca see the routes found by igrp. A route discovered by igrp is denoted by letter "I" before start of the entry.

51. 7 steps in building a Prototype are:

• Review the customer's requirement

• Determine the extent of the prototype

• Understand your competition

• Develop a test plan

• Purchase and prepare equipment

• Practice

• Conduct final tests and demonstrations

52. Default administrative distances are as below:

Route Source	Default Distance
Directly connect Interface	0
Static Route	1
EIGRP Summary Route	5
Internal EIGRP	90
IGRP	100
OSPF	110
RIP	120
Unknown	255

The administrative distance (metric) is used to represent the trustworthiness of the route. Lower the value, higher the trustworthiness. A value of 255 represents that the route is unreachable.

53. Private addresses are described in RFC 1918. There are one Class A network, 16 Class B networks and 255 Class C networks that belong to private address space. There are:

Class Type	Start Address	Stop Address
Class A	10.0.0.0	10.255.255.255
Class B	172.16.0.0	172.31.255.255
Class C	192.168.0.0	192.168.255.255

The above address range is reserved for private use.

54. Cisco IOS supports

• Priority Queuing is useful for time sensitive, mission critical protocols such as SNA.

• Custom queuing handles the queues in round robin fashion.

• Weight Fair Queuing is enabled by default and requires no configuration.