tut 1 lan redundancy question

BAIT3094 Advanced Computer Networks 1

MAY 2015

Tutorial 1: (Chapter 1 LAN Redundancy)

1. Match the different varieties of STP with its characteristics. (Some characteristics apply to more

than one STP variety.)


MAY 2015

2. (a) Spanning Tree Protocol (STP) was developed to address the issue of loops in a redundant

switch-based network.

(i) With reference to Figure 2-1, you are required to draw a logical loop-free Spanning Tree topology diagram in your answer booklet. In addition, determine the root bridge

and ALL port roles in the diagram. (6 marks)

Figure 2-1: A network topology

(ii) Illustrate THREE (3) potential issues that would occur if STP was not implemented. (6 marks)

(iii) In your option, what is the port state that switch ports immediately transition to when configured for PortFast? Justify your answers. (3 marks)

.


MAY 2015

3. Spanning Tree Protocol (STP) was developed to address the issue of loops in a redundant switch-

based network, such as the one shown in Figure 3-1. (2012 Adv)

Figure 3-1 A Redundant Switch-based Network

(i) Illustrate TWO (2) main functions of the Spanning Tree Algorithm (STA) used

in STP. (4 marks)

(ii) With reference to Figure 3-1, you are required to draw a logical loop-free

Spanning Tree topology diagram in your answer booklet. Identify the port roles

in the diagram. (4 marks)

(iii) Is the active switched path for Host_P to access to the Server the optimal path?

Explain your answer. If not, identify the optimal path and explain how you could

achieve this. (5 marks)

4. Analyze Figure 4-1 below and explain why switch S2 was not been elected as the root bridge for

VLAN1. (5 marks)

S2#show spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 24577

Address 0050.0F68.146E

Cost 19

Port 3(FastEthernet0/3)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 28673 (priority 28672 sys-id-ext 1)

Address 00E0.F7AE.7258

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 20


MAY 2015

Interface Role Sts Cost Prio.Nbr Type

----------- ----- ------ ------ --------- ------

Fa0/3 Root FWD 19 128.3 P2p

Fa0/2 Desg FWD 19 128.2 P2p

Fa0/1 Desg FWD 19 128.1 P2p

Fa0/4 Altn BLK 19 128.4 P2p

Figure 4-1: Output of show spanning-tree vlan 1

5. (i) Analyze Figure 5-1. A network engineer is troubleshooting host connectivity on a LAN

that uses a First Hop Redundancy Protocol (FHRP). Determine IPv4 gateway address that

should be configured on the hosts that are connected to the LAN. Justify your answers.

(4 marks)

Figure 5-1: FHRP

(ii) Differentiate two types of protocol in the First Hop Redundancy Protocol (FHRP).

(6 marks)

6. When troubleshooting an EtherChannel issue, illustrate the configuration restrictions for

interfaces that participate in the channel.

R1#show standby

GigabitEthernet0/1 - Group 1 (version 2)

State is Active

7 state changes, last state change 00:00:30

Virtual IP address is 192.168.1.254

Active virtual MAC address is 0000.0C9F.F001

Local virtual MAC address is 0000.0C9F.F001 (v2 default)

Hello time 3 sec, hold time 10 sec

Next hello sent in 2.977 secs

Preemption enabled

Active router is local

Standby router is 192.168.1.3, priority 150 (expires in 7 sec)

Priority 150 (configured 150)

Group name is hsrp-Gig0/1-1 (default)


MAY 2015

7. (a) Explain why the EtherChannel between S1 and S2 is down.

S1# show etherchannel summary

Flags: D - down P - bundled in port-channel

I - stand-alone s - suspended

H - Hot-standby (LACP only)

R - Layer3 S - Layer2

U - in use f - failed to allocate aggregator

M - not in use, minimum links not met

u - unsuitable for bundling

w - waiting to be aggregated

d - default port

Number of channel-groups in use: 1

Number of aggregators: 1

Group Port-channel Protocol Ports

------+-------------+-----------+-----------------------------------------------

1 Po1(SD) - Fa0/1(D) Fa0/2(D)

---------------------------------------------------------------------------------------------

S1# show run | begin interface Port-channel

interface Port-channel1

switchport mode trunk

!

interface FastEthernet0/1


channel-group 1 mode auto

!




!

S 1#

---------------------------------------------------------------------------------------------

S2# show run | begin interface Port-channel

interface Port-channel1


!



channel-group 1 mode auto chg to desirable !





MAY 2015

Both sides of the link are set to the PagP auto mode, which means that the interface

will listen for PagP packets but will not initiate negotiations. Neither side initiaties

negotiation, so the channel is down.

(b) What would you suggest to correct the issue shown in Q11(a) if the requirement is to use

PAgP?

8. An EtherChannel was configured between switches S1 and S2, but the interfaces do not form an

EtherChannel.

Figure 8-1: A network topology

(i) A Junior Network Engineer seeks your expertise to identify and solve the problem as depicted in Figure 8-1 above. (6 marks)

Chg S1 to vlan 1,5,10 or Chg S2 to vlan 1-5,10

(ii) Based on Figure 8-1, the EtherChannel link was configured between two switches, S1 and S2 using Port Aggregation Protocol (PAgP) or Link Aggregation Control

Protocol (LACP)? Explain the configured protocol.

(4 marks)

The mode is active, both switches are active, indicating LACP is on S1,S2. Interchannel and multi-

vendor environment.

LSDP is a IEEE standard, it can use to facilitate multi channel in multi vendor environment.

tut 1 lan redundancy question

Documents