1.3 Sample CCNA exam (OSI and TCP/IP Model)

This sample CCNA exam will review your knowledge about OSI and TCP/IP Model.

Questions :

1. You issue ping command and you get output shows “request times out”. Which OSI layer this problem reside ?
2. Which layer of the OSI model is responsible for ensuring reliable end-to-end delivery of data?
3. At which OSI layer is a logical path created between two host ?
4. The acknowledgement of transmissions, sequencing, and flow control across a network. At which OSI layer ?

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Answers :

1. Network layer
   ICMP is a protocol designed to help manage and control the operation of a TCP/IP network. The ICMP protocol provides a wide variety of information about a network's health and operational status. Ping belong to this ICMP, and ICMP belong to Network layer in OSI layer.
2. Transport layer
   
3. Network layer
   
4. Transport layer
   

1.2 Devices required to meet a network specification

As mentioned in section 1.1, we already knows something about router, switch, and hub, also bridge as addition in internetwork. Figure below shows how network look with all of those internetwork devices in place. Please note that left and right part of this figure are not commonly use this day (we can say that bridge and hub are old technology). Typical network this day can be found in middle part (switch 1, 2, and 3).

Figure 1

Remember that a router will not only break up broadcast domain in every LAN interfaces, but also it will break up collision domain as well.

Notice that we use bridge, it break up collision domain, operate similary with switch. Hub does not break up collision domain, we can say that every devices connected to hub belong to the same collision domain.

The best network connected to the router is the LAN switch network in the middle. Why ? Because each port on switch has its own collision domain. Well, we still can enhance this LAN switch in the middle. Since its still belong to the same broadcast domain, it can turn into bad thing. Imagine if the broadcast domain too large, so all devices must listen to all broadcast transmitted, the users then have less bandwidth and require to proccess more broadcast, as result network response time will slow. We can do enhancement by using separate VLAN (Vitual LAN) for each switches to meet bussiness requirement. For example Switch 2 using VLAN 100 to serve users in IT Departement, Switch 3 using VLAN 200 to server Accounting Departement. This will separate or break up broadcast domain, router still need for interVLAN communication.

Ok, let’s back to Figure 1 above ..
How many broadcast and collision domains are in this internetwork ?
Leave your answer in comment box below .. C U..

1.1 Sample CCNA exam (Describe how a network works)

This sample CCNA exam intend to review your knowledge about segment 1.1 Describe the purpose and functions of various network devices on Cisco CCNA 640-802 exam blue print. So, did you know already ?

Questions :

1. What is biggest benefit of using switch instead hub for network connectivity in LAN ?
2. Explain true characteristics regarding the use of hubs and switches ..
3. Mention functions of a router ..
4. Network devices : switch, hub, bridge, and repeater. Categorise those network devices based on what OSI layer they operate ..
5. Giving device capabilities : Allowing simultaneous frame transmissions and Filtering frames based on MAC addresses. What device has both capabilities ?
6. Network administrator want to replace a hub on LAN with switch, what two results would occurs ?

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Answers :
Please read archive with tag/label Describe how a network works for detail explanations.

1. The biggest benefit of using switches instead of hubs in your internetwork is that each switch port is actually its own collision domain (we can say switch increase the number of collision domains). Hub creates only one large collision domain
2. Please find the drawbacks of Hub and advantages of Switch
3. Basicly, function of the router are to interconnecting networks by selecting best path (routing/path selection) for a packet to travel, and forward packet (packet switching) to outgoing interface using best path in routing table. As an additional feature, routers are capable of providing filtering on a network address and application port level (Access Controll List).
4. Layer 1 devices : hub and repeater.
   
   
   
   Hub actually performs OSI layer 1 functions, repeating an electrical signal. Repeater does not interpret what the bits mean, but does examine and generate electrical signals, a repeater is considered to operate at Layer 1.
   Layer 2 devices : bridge and switch.
   Both bridges and switches operate at the second layer of the OSI model, rocessing and forwarding frames from the data-link layer. Bridges are software based and switches are hardware based. Switches have more ports than bridges. Both ridges and switches forward frames based on MAC addresses.
5. Switch
6. 
   
   The number of broadcast domains would remain the same, the number of collision domain would increase