Saturday, April 11, 2015

Random Cisco based networking questions - CCNA - Part 4

Welcome to part 4 of the random networking questions (Cisco based) series.  This set has a few extra spanning tree questions with detailed explanations, have fun :-)

1. What is the default time Bridge Protocol Data Units (BPDUs)  are sent and received by switches?

A) 2 seconds
B) 10 seconds
C) 30 seconds
D) 60 seconds

2. What does the following statement do?

Switch(config-if)#spanning-tree portfast disable

A) Disables spanning-tree on the switch port
B) Disable spanning tree on the switch
C) Changes the spanning-tree switch to portfast mode

3. What determines network addresses (IP) when data link addresses (MAC) are known?

A) Ping

4. The Cisco Spanning Tree protocol is compatible with IEEE 802.1d?

A) True
B) False

5. What type of switch port can belong to multiple VLANS?

A) Access port
B) Trunk port
C) Voice access port
D) No port can belong to multiple VLANs

6.What will be the IP address of the second subnet given the following? (Assume ip subnet-zero is enabled)


Speaking of IP, I sometimes use a simple little site that gives you your own IP and other internet connectivity details   - IP Chicken - handy link  :-)

1. Answer A

Bridge Protocol Data Units (BPDUs) frames are sent out as multicast messages regularly at multicast destination MAC address 01:80:c2:00:00:00. When Bridge Protocol Data Units (BPDUs) are received, the Switch uses a mathematical formula called the Spanning Tree Algorithm (STA) to know when there is a Layer 2 Switch loop in network and determines which of the redundant ports needs to be shut down.

Three types of Bridge Protocol Data Units (BPDUs) are Configuration BPDU (CBPDU), Topology Change Notification (TCN) BPDU and Topology Change Notification Acknowledgment (TCA).

2.  Answer A

The time Spanning Tree Protocol (STP) takes to transition ports over to the Forwarding state can cause problems. PortFast is a Cisco network function which can be configured to resolve this problem by disabling STP from the switchport, thus making it come up quicker.

3. Answer D

Reverse Address Resolution Protocol (RARP) is used by a host computer to request its IPv4 address from an administrative host (DHCP server), it provides the server with its hardware address (MAC address).

NOTE: Dynamic Host Configuration Protocol (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address and other related configuration information such as the subnet mask and default gateway.

4.  Answer B

The original Spanning-Tree protocol was created by Digital Equipment Corporation (DEC) which is now part of Compaq. The IEEE created its own version called IEEE 802.1d which is not compatible with the original version.

Cisco enhanced the original 802.1d specification with features such as Uplink Fast, Backbone Fast, and Port Fast to speed up the convergence time of a bridged network. However these new features are proprietary, and can only be configured on Cisco switches.

5. Answer B

Ethernet interfaces can be configured either as access ports or trunk ports. Trunks carry the traffic of multiple VLANs over a single link and allow you to extend VLANs across the network.

6. Answer D 

The subnet block size is 256 - 224 = 32
The first subnet will be subnet zero
The second subnet will be

How did you go? I find a quick review of the questions and answers helps cement the basics and refresh the memory  - I hope these help, stay tuned for more...

The secret of life is not to do what you like but to like what you do.
By: Anonymous