Tut 1 Lan Redundancy Question
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Transcript of Tut 1 Lan Redundancy Question
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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.)
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BAIT3094 Advanced Computer Networks 2
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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)
.
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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
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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)
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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)
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S1# show run | begin interface Port-channel
interface Port-channel1
switchport mode trunk
!
interface FastEthernet0/1
switchport mode trunk
channel-group 1 mode auto
!
interface FastEthernet0/2
switchport mode trunk
channel-group 1 mode auto
!
S 1#
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S2# show run | begin interface Port-channel
interface Port-channel1
switchport mode trunk
!
interface FastEthernet0/1
switchport mode trunk
channel-group 1 mode auto chg to desirable !
interface FastEthernet0/2
switchport mode trunk
channel-group 1 mode auto
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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.