Learn About Interconnecting Cisco Networking Devices, Part 2

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These questions are based on 640-816: Interconnecting Cisco Networking Devices, Part 2

A Self Test Software Practice Test

Objective: Configure, verify and troubleshoot a switch with VLANs and inter-switch communications.

Sub-objective: Describe enhanced switching technologies, including VTP, RSTP, VLAN, PVSTP and 802.1q.

Multiple answer, multiple-choice

Which three ports in the diagram will be operating as designated ports? (Choose three.)

A. SwitchA F0/1

B. SwitchB F0/1

C. SwitchC F0/1

D. SwitchA F0/2

E. SwitchB F0/2

F. SwitchC F0/2

Answer:

A. SwitchA F0/1

B. SwitchB F0/1

D. SwitchA F0/2

Tutorial:
SwitchA port F0/1, SwitchA port F0/2 and SwitchB port F0/1 will be operating as designated ports. Designated ports are forwarding ports leading away (downstream) from the STP root switch. To determine which ports will be designated, the root switch must first be identified. The switch with the lowest bridge ID will be selected as the root bridge by STP.

A bridge ID has two components: the priority number and the MAC address. If the priorities match, then the switch with the lowest MAC address becomes the root bridge. In the exhibit, SwitchA has the lowest MAC address, so SwitchA becomes the root bridge. Every port on the root switch automatically becomes a designated port, and the ports on SwitchB and SwitchC that connect them to the root bridge are called root ports. Since SwitchA is the root bridge, ports F0/1 and F0/2 on SwitchA are designated ports.

The third designated port will be located on the segment between SwitchB and SwitchC. STP will have to assign this segment to one of the two switches to prevent redundancy and switching loops in the spanning tree itself. Since SwitchB has the lower MAC address, the segment will be handled by SwitchB, and its port F0/1 will become a designated port.

Port F0/2 on Switch C will become a blocking port.

References:

CCNA ICND2 Official Exam Certification Guide, Chapter 2: Spanning Tree Protocol, pages 67-72.

Cisco > Catalyst 6500 Series Cisco IOS Software Configuration Guide, 12.1E > Configuring STP and IEEE 802.1s MST > Election of the Root Bridge

Objective: Implement an IP addressing scheme and IP services to meet network requirements in a medium-size enterprise branch office.

Sub-objective: Determine the appropriate classless addressing scheme using VLSM and summarization to satisfy addressing requirements in a LAN/WAN environment.

Single answer, multiple-choice

In the given network diagram, what will be the broadcast address for the subnet to which Host A is connected?

A. 172.32.2.255

B. 172.32.3.255

C. 172.32.4.255

D. 172.32.5.255

Answer:

B. 172.32.3.255

Tutorial:

The broadcast address 172.32.3.255 is correct.

Network address: 172.32.2.0
Subnet mask in decimal: 255.255.254.0
Subnet mask in binary: 11111111.11111111.11111110.00000000

The formulae to calculate the number of subnets and hosts are:

Number of subnets = 2number-of-subnet-bits
Number of hosts per subnet = 2number-of-host-bits - 2
Number of host bits in a mask = (Total number bits in an IP address) - (Number of network bits)

In this scenario, we have:

Number of subnet bits = 7 (the number of binary 1s in the subnet octet of the subnet mask)

Number of host bits: 32 - 23 = 9
Number of subnets: 27 = 128
Number of hosts: 29 - 2 = 510

All the other options are incorrect because none of these will be the broadcast address for the subnet to which Host A is connected.

A note about the formulas: You will always subtract 2 from the number of hosts (2number-of-subnet-bits - 2) because the all-zero bit address is reserved for the network address, and the all-one bit address is reserved for the broadcast address.

References:

Cisco > Technology Support > IP > IP Routing > Design Technotes > IP Addressing and Subnetting for New Users > Document ID: 13788 > Understanding IP Addresses

CCNA ICND2 Official Exam Certification Guide, Appendices D, E and H: Subnetting.

Objective: Configure and troubleshoot basic operation and routing on Cisco devices.

Sub-objective: Compare and contrast methods of routing and routing protocols.

Multiple answer, multiple-choice

Which commands would be used to enable Routing Information Protocol (RIP) on a router and configure the IP addresses 10.2.2.2 and 11.2.1.2 as a part of complete RIP configuration? (Choose three.)

A. router rip

B. router rip 5

C. network 10.2.2.2

D. network 10.0.0.0

E. network 11.2.1.2

F. network 11.0.0.0

Answer:

A. router rip

D. network 10.0.0.0

F. network 11.0.0.0

Tutorial:

The router rip command is used to enable RIP on a router. The network 10.0.0.0 and network 11.0.0.0 commands are used to activate RIP over the interfaces configured with IP addresses 10.2.2.2 and 11.2.1.2. The network commands in RIP configuration ignore any subnet-specific information.

Since both IP address 10.2.2.2 and 11.2.1.2 are Class A IP networks and only the first octet (byte) of a Class A IP address represents the major (classful) network, the remaining bytes are ignored by the network command. Thus, even if a network 10.2.2.2 were configured, the Cisco IOS would truncate it to network 10.0.0.0 automatically.

The following commands are used to configure RIP on a router:

router(config)# router rip
router (config-router)# network x.x.x.x
router (config-router)# network y.y.y.y

The parameters of network command are:

x.x.x.x - This is the major (classful) network number connected to the router.
y.y.y.y - This is the other major (classful) network number connected to the router.

The router rip 5 command is incorrect because RIP does not require a keyword when enabling the protocol.

The network 11.2.1.2 and network 10.2.2.2 are incorrect because network 10.0.0.0, and network 11.0.0.0 commands are used to configure IP addresses 10.2.2.2 and 11.2.1.2 as a part of RIP configuration.