Scenario:
CiscoSims is an Internet game provider. The game service network had recently added an additional switch block with multiple VLANs configured. Unfortunately, system administrators neglected to document the spanning tree topology during configuration. For baseline purpose, you will be required to identify the spanning-tree topology for the switch block.
Using the output of "show spanning-tree" command on switch SW-C and the provided physical topology, answer the following questions:
Questions & Answers:
Question 1:
Which spanning Tree Protocol has been implemented on SW-B?
A. STP/IEEE 802.1D
B. MSTP/IEEE 802.1s
C. PVST+
D. PVRST
E. None of the above
Explanation:
802.1D has not been implemented since this is CST (Common Spanning Tree) which only allows one instance to be run at a time per Network. In this scenario there are multiple instances. It must be PVST+ since each instance only contains one VLAN.
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Question 2:
Which bridge ID belongs to SW-B?
A. 24623.000f.34f5.0138
B. 32768.000d.bd03.0380
C. 32768.000d.65db.0l02
D. 32769.000d.65db.0l02
E. 32874.000d.db03.0380
F. 32815.000d.db03.0380
Explanation:
Root ports are ports that point to the Root Bridge. In the exhibit, under VLAN 47 we see that fa0/2 is a root port for VLAN 47. Since we assume that all paths have equal cost we can gather that the root ports destination is the root bridge itself. In this case the Root Bridge for VLAN 47 is SW-B and according the exhibit the MAC address is 24623 000f 34f5 0138
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Question 3:
Which port role has interface Fa0/2 of SW-A adopted for VLAN 47?
A. Root port
B. Nondesigned port
C. Designated port
D. Backup port
E. Alternate port
Explanation:
Refer to Explanation for previous question. So far we know that SW-B is the Root Bridge for VLAN 47. We also see that SW-C is using fa0/2 as its root port. Therefore SW-A will use fa0/1 for its Root port and fa0/2 will be designated since fa0/1 on SW-C is blocking. Note: If one segment of SPT is in blocking statusthe distantend port is not. Otherwise BPDUs could not be transmitted and would negate the redundancy.
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Question 4:
Which port state is interface Fa0/2 of SW-B in for VLANs 1 and 106?
A. Listening
B. Learning
C. Disabled
D. Blocking
E. Forwarding
F. Discarding
Explanation:
For VLAN 1 and 106 we can conclude that the Root Bridge is SW-A. With this in mind SW-B will use fa0/1 for its root port and block the other since the Cost will be lower. In this case it will block fa0/2 for both VLANs (and most likely fa0/3 also since SW-D is using fa0/1 as its root port).
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Question 5:
Which bridge ID belongs to SW-A?
A. 24623.000f.34fS.0138
B. 32768.000d.bd03.0380
c. 32768.000d.65db.0102
D. 32769.000d.65db.0102
E. 32874 .000d .db03.0380
F. 32815.000d.db03.0380
Explanation:
We see that in VLAN 1 and VLAN 106 that fa0/1 is the root port on SW-C. As previously discussed we know that root ports point to the root bridge and assuming equal cost from switch to root and the fact that no other port is root for either VLAN that SW-A is the Root Bridge and we can gleen the information for the exhibit which list the Bridge's VLAN.
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Sunday, September 27, 2009
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About Q4,
ReplyDeleteShouldn't it be Discarding since RSTP protocol is used ? There are only 3 states for RSTP: Discarding, Learning, and Forwarding.
Good question!
ReplyDeleteIn the 'show span' command, you can see that the fa0/2 of SW-C is changed to STP, because it is connected to a switch running STP. So the state of Fa0/2 of SW-B is not discarding, but blocking.
Oh, that's right ! Thanks, ciscosims.
ReplyDeleteAbout Q4 and Q1:
ReplyDeleteIf SW-C fa 0/2 is STP then SW-B should be running 802.1D for Q1
No, STP also means PVST+
ReplyDeleteIt cant be 802.1d coz there are multiple instances.
About Q4 and Q1
ReplyDeleteType P2P Peer(STP)represents that the neighboor is running PVST because of that on Q1 the answer is "D"
If you see P2p Peer(STP), the port is a point-to-point type but the neighboring device is running
ReplyDeletetraditional 802.1D STP.
So the answer for Q1 is "A"
see reference on Cisco Press BCMSN
Page 272
Hello,
ReplyDeleteI found that Study Guides are often ambiguous and vague about "show" questions.The best way to sovle "show" question is to look for this command or output on cisco.com site. 95% of such questions are directly from cisco online docs.
In this case, go cisco.com -> search "P2p peer (STP)" -> bingo!:
!--- Type P2p peer (STP) represent that the neighbor switch runs PVST
Hi finaly what are the answers. As someone wrote in question 1 I have read in BCMSN study quide "If you see P2p Peer(STP), the port is a point-to-point type but the neighboring device is running
ReplyDeletetraditional 802.1D STP."
in question 5:
for vlan 101 has root priority 24682 so I think there are no equal bridge ID(could be find at Switch#sh spann bridge)
And finaly: I heard there are some new sims and questions in BCMSN. Do you know something about it?
HI it is avalid Hotsport Question for BCMSN... let me know even know me latest for the same
ReplyDeletefa0/1 is root ports for VLAN 1,106
ReplyDeletesw-a - probably root, then see bridge id in listening commands:
Root ID priority for VLAN 1: 32769
ROOT ID priority for VLAN 106: 24682
why answer D. 32769.000d.65db.0102 ???
Hi my sweet Buddy’s,
ReplyDeleteToady I completed my CCNP Composite exam & scored 991/1000.
Questions are from Test-inside dumps TI 5.25, it’s a valid one.
Got 4 SIMS:
AAA DOT1X Radius
IPV6 Virtual Link
EIGRP ISIS redistribution
EIGRP Stub
3 SPOT
HSRP
EIGRP Simlet
Spanning tree
No Drag & Drop……………………
Best of Luck guys…………. Only 1 day is left
Thanks to ciscosims……… It’s a nice site to refer………