VTP Lab 2
Question:
Acme is a small export company that has an existing enterprise network comprised of 5 switches;
CORE,DSW1,DSW2,ASW1 and ASW2. The topology diagram indicates their desired pre-VLAN spanning tree mapping.
Previous configuration attempts have resulted in the following issues:
– CORE should be the root bridge for VLAN 20; however, DSW1 is currently the root bridge for VLAN 20.
– Traffic for VLAN 30 should be forwarding over the gig 1/0/6 trunk port between DSW1 and DSW2. However VLAN 30 is currently using gig 1/0/5.
– Traffic for VLAN 40 should be forwarding over the gig 1/0/5 trunk port between DSW1 and DSW2. However VLAN 40 is currently using gig 1/0/6.
You have been tasked with isolating the cause of these issuer and implementing the appropriate solutions. You task is complicated by the fact that you only have full access to DSW1, with isolating the cause of these issues and implementing the appropriate solutions. Your task is complicated by the fact that you only have full access to DSW1, with the enable secret password cisco. Only limited show command access is provided on CORE, and DSW2 using the enable 2 level with a password of acme. No configuration changes will be possible on these routers. No access is provided to ASW1 or ASW2.
Answer and Explanation:
1) “CORE should be the root bridge for VLAN 20; however, DSW1 is currently the root bridge for VLAN 20″ -> We need to make CORE switch the root bridge for VLAN 20.
By using the “show spanning-tree” command as shown above, we learned that DSW1 is the root bridge for VLAN 20 (notice the line “This bridge is the root”).
DSW1>enable
DSW1#show spanning-tree
To determine the root bridge, switches send and compare their priorities and MAC addresses with each other. The switch with the lowest priority value will have highest priority and become the root bridge. Therefore, we can deduce that the priority of DSW1 switch is lower than the priority of the CORE switch so it becomes the root bridge. To make the CORE the root bridge we need to increase the DSW1′s priority value, the best value should be 61440 because it is the biggest value allowed to assign and it will surely greater than of CORE switch. (You can use another value but make sure it is greater than the CORE priority value by checking if the CORE becomes the root bridge or not; and that value must be in increments of 4096).
(Notice that the terms bridge and switch are used interchangeably when discussing STP)
DSW1#configure terminal
DSW1(config)#spanning-tree vlan 20 priority 61440
2) “Traffic for VLAN 30 should be forwarding over the gig 1/0/6 trunk port between DSW1 and DSW2. However VLAN 30 is currently using gig 1/0/5″
DSW1 is the root bridge for VLAN 30 (you can re-check with the show spanning-tree command as above), so all the ports are in forwarding state for VLAN 30. But the question said that VLAN 30 is currently using Gig1/0/5 so we can guess that port Gig1/0/6 on DSW2 is in blocking state (for VLAN 30 only), therefore all traffic for VLAN 30 will go through port Gig1/0/5.
The root bridge for VLAN 30, DSW1, originates the Bridge Protocol Data Units (BPDUs) and switch DSW2 receives these BPDUS on both Gig1/0/5 and Gig1/0/6 ports. It compares the two BPDUs received, both have the same bridge-id so it checks the port cost, which depends on the bandwidth of the link. In this case both have the same bandwidth so it continues to check the sender’s port id (includes port priority and the port number of the sending interface). The lower port-id value will be preferred so the interface which received this port-id will be the root and the other interface (higher port-id value) will be blocked.
In this case port Gig1/0/6 of DSW2 received a Priority Number of 128.6 (means that port priority is 128 and port number is 6) and it is greater than the value received on port Gig1/0/5 (with a Priority Number of 128.5) so port Gig1/0/6 will be blocked. You can check again with the “show spanning-tree” command. Below is the output (notice this command is issued on DSW1 – this is the value DSW2 received and used to compare).
Therefore, all we need to do is to change the priority of port Gig1/0/6 to a lower value so the neighboring port will be in forwarding state. Notice that we only need to change this value for VLAN 30, not for all VLANs.
DSW1(config)#interface g1/0/6
DSW1(config-if)#spanning-tree vlan 30 port-priority 64
DSW1(config-if)#exit
3) “Traffic for VLAN 40 should be forwarding over the gig 1/0/5 trunk port between DSW1 and DSW2. However VLAN 40 is currently using gig 1/0/6″
Next we need to make sure traffic for VLAN 40 should be forwarding over Gig1/0/5 ports. It is a similar job, right? But wait, we are not allowed to make any configurations on DSW2, how can we change its port-priority for VLAN 40? There is another solution for this…
Besides port-priority parameter, there is another value we can change: the Cost value (or Root Path Cost). Although it depends on the bandwidth of the link but a network administrator can change the cost of a spanning tree, if necessary, by altering the configuration parameter in such a way as to affect the choice of the root of the spanning tree.
Notice that the Root Path Cost is the cost calculated by adding the cost in the received hello to the cost of the interface the hello BPDU was received. Therefore if you change the cost on an interface of DSW1 then only DSW1 will learn the change.
By default, the cost of a 100Mbps link is 19 but we can change this value to make sure that VLAN 40 will use interface Gig1/0/5.
DSW1(config)#interface g1/0/5
DSW1(config-if)#spanning-tree vlan 40 cost 1
DSW1(config-if)#end
You should re-check to see if everything was configured correctly:
DSW1#show spanning-tree
Save the configuration:
DSW1#copy running-config startup-config
(Notice: Many reports said the copy running-config startup-config didn’t work but they still got the full mark)
Remember these facts about Spanning-tree:
Path Selection:
1) Prefer the neighbor advertising the lowest root ID
2) Prefer the neighbor advertising the lowest cost to root
3) Prefer the neighbor with the lowest bridge ID
4) Prefer the lowest sender port ID
Spanning-tree cost:
Other good resource for reference:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800ae96a.shtml
Other lab-sims in this site:
LACP with STP Sim
MLS and EIGRP Sim
VTP Lab
Spanning Tree Lab Sim
AAAdot1x Lab Sim
Switch DSW1 is root bridge (Upstream) for Vlan30 and Downstream for vlan 40.
Switch DSW2 is root bridge (Upstream) for Vlan40 and Downstream for vlan 30.
To influence which port is elected the root port, the two user configurable values to change are port cost and port priority. Port-priority is set on an upstream switch to influence a downstream switch and Cost is set on downstream switch to influence a upstream switch.
For this scenario, your rules work. For real life, port-priority and path cost can be used on either side of the path.
thank you.that’s very good lab.I’m sure that’s exam sim.
Did anybody ever get this in your exam? (in recent exams after July 31st?
thanks
BIP-DOOO
No that isn’t correct.
If you have a switch that isn’t the root switch but has two uplinks as per above then the root switch will be FWD on both ports and the non-root switch will have to block a port to prevent a loop forming.
You have to manipulate cost on the non root switch if you can manipulate port priority on the root.
for the requirement
DSW1(config)#interface g1/0/5
DSW1(config-if)#spanning-tree vlan 40 cost 1
can i make it as
DSW1(config)#interface g1/0/6
DSW1(config)#spanning-tree vlan 40 port-priority 240 —> this makes g1/0/5 port priority less
then traffic will pass througe g1/0/5
???
@Ahmed Adel
recall the sequence of the four criteria that STP uses to choose a path
1. Lowest bridge ID
2. Lowest root path cost
3. Lowest sender bridge ID
4. Lowest SENDER port ID
root path cost is the cumulative – ingress at the interface
lower port priority value indicates a more preferred path toward the root
this information is in the BPDU
thats the way i understand it – 7 more days to 642-813
Who do I talk to about submitting a Packet Tracer lab sim for this… I was able to simulate everything but unfortunately Packet Tracer doesnt allow you to use the spanning-tree vlan cost command so question 3 is un-doable but everything else is working good and it looks clean.. I would love to share, this site is definitely a major asset to anyone looking to take CCNP exams.
Packet Tracer is basically useless once you get past the CCNA.
Superb blog post, I have book marked this internet site so ideally I’ll see much more on this subject in the foreseeable future!
is this sim still valid??
Thanks for your lab. I’m going to take CCNP Swiching. Thanks again.
Why cant we use the command spanning-tree vlan xx cost 1 (where xx refers to either vlan 30 or 40) in both the cases. Can someone please explain why we use port-priority in one case and cost on the other?
Thank you. This configuration is correct. I’ve tested on my lab. I’m going to take 642-813 exam next week. Update later.
@Raj: Cause the first, DSW1 is root switch, so we cannot alter the cost from any port to root switch (amazing).
@Ahmed Adel : Cannot do like you. Cause the DSW1 is not root switch for VLAN 40, in other way, the switch A does not send any BPDU about VLAN 40.
Really this is what the SWITCH exam is like? I just finished the cisco netacadamy class and it did not prepare the class for a question anything like this. How can they give questions they don’t prepare you for? Now I am nervous about taking the test.
Is this lab appearing for the exam these days?
Hello Friends,
Can anyone of please send me the latest CCNP switch dumps and the crack to open .vce files and the packet tracer lab files at t2b2l2@yahoo.com.
Thank you very much.
Actually this is STP Lab, not VTP
I took this test twice 642-812.
This sim was on it both times. It is a complicated troubleshooting exercise but the solution it minimal.
DSW1(config)# spanning-tree vlan 20 priority 61440
DSW1(config)# interface g1/0/6
DSW1(config-if)# spanning-tree vlan 30 port-priority 64
DSW1(config-if)# interface g1/0/5
DSW1(config-if)# spanning-tree vlan 40 cost 1
HI all¡¡
This practice its for the 642-813 or only to the 642-812¿??¿
@ all
Anyone can plzz explain who all had got this ;ab for exam recently.
Coz mostly they are getting Lacp with stp.
Anyways if the solution is minimal we can always be prepared for this as well
Please, This practice its for the 642-813 or only to the 642-812¿??¿
i think this can works:
dsw1(config)#spanning-tree vlan 40 root primary
sorry
dsw1(config)#spannig-tree vlan 40 root secondary ?¿¿?
Actually are the labs on switch exam?
There are 3 to 4 Labs in the Switch Exam Boss (i.e Eigrp,VTP,VTP2 & aaa)
Anyone have idea about a simulation question [not VTP,VTP2, MLS with EIGRP, LACP with STP, STP, AAAdot1X] in almost all the dumps (P4S, Testking, flipper) with very long IOS commands as step 1, 2, 3,,,,,,,,,,, Becoz it’s too many pages. Need lot of time to finish.. Will it come for exam? Plz anyone tel me…!
yes. at most 3. but if you are unlucky you will get 4 labs.
are these still the latest labs. pls i need an urgent answer. i want to write this week
what is pass mark now for new switching
790
hi guys
please send me the link for ccnp switch 642-813 dumps i need it.
Is there any limitation in the question not to change DSW1′s priority for VLAN 40?
It seems to me there’s another way to achieve this goal:
DSW1#configure terminal
DSW1(config)#spanning-tree vlan 40 priority 28672 (or any other number LOWER than DSW2′s VLAN 40 priority which can be seen in “show spanning-tree”, making DSW1 root for VLAN 40)
DSW1(config)#interface g1/0/5
DSW1(config-if)#spanning-tree vlan 40 port-priority 64
Actually the last line is not needed because g1/0/5′s priority for VLAN 40 is 128.5 which is lower than g1/0/6′s.
Can anyone confirm this is a working solution not violating any requirement?
@bentz
i think everyone forgets that the exam runa a switch simulator.
just follow what is written here.
@Pika
I fail to see the rellevance in your post. All I was saying was that what worked for VLAN 20 should also work fo VLAN 40.
I am struggling to find a better way to practice CCNP SWITCH LABS. ANYHELP?. In return i will give you the latest dump from p4sure & TE including other googies that will blow your mind away.
hi! just a question, do you have to clear / reset the port on DSW1 to update the stp port status on the vlan 30 question? tried it in the packet tracer and i did have to refresh the ports so vlan 30 would use Gi1/0/6. thanks
These are great example and are very clear.
Thanks buddy. please post like these examples if possible.
Hello all could some one provide us with a link to down load simulation labs and practice on them for exam
it will be very helpful i search every were and i didnt find this labs
thanks in advance
saadhh_007@yahoo.com
This site is very good keep he good work guys
@DBW f you want a full simulation use gns3 . Its free , just google it
guys would you be so kind sending me the right dump files for the exam on neshoa@abv.bg
I have non of them. plssssss
thanks in advance
can someone pls explain why we cant alter the cost of the link/interface for vlan 30. why must we use port-priority?
thanks
@r2g
What it doesn’t tell you in the above sim, is that you only have full commands on DSW1 and the other two switch you can only do show commands.
So all the config changes have to be on DWS1. So depending on who is the ROOT depends on which commands we can use. For VLAN 30 we change the port cost to make that link better. For VLAN 40 we change the port priority because we can’t change the port cost as port cost is calculated from the root outwards.
Single STP allows all the VLANs to run STP but each VLAN runs the same instance of STP resulting in numerous blocked ports that do not pass any Layer 2 traffic. STP per VLAN group uses all available links by load balancing traffic for different instances of STP on different ports.
can anybody send me the latest dumps at waheed.nse@gmail.com please.I am going for CCNp switch next week
Your asnwer was just what I needed. Its made my day!
my exam after 12h and 30 min
Hi guys .
As I did not find a pkt for this lab I decided to make one myself. If someone wants it you can find it here:
http://www.4shared.com/file/FtH3Eo9C/VTP_LAB2.html
I couldn’t set the exact interfaces but made a map so you can figure out quickly. If you find any errors please let me know and I will try to fix it. Any feedback is appreciated.
Thanks.
Please update the url to: http://www.4shared.com/file/0djjfdHM/VTP_LAB2.html
On the cisco website the criteria 4 root path selection says:
1. Path cost
2. The bridge ID of the forwarding switch
3. Lowest port priority
4. Lowest internal port number
as opposed to the list given in the explanation:
1) Prefer the neighbor advertising the lowest root ID
2) Prefer the neighbor advertising the lowest cost to root
3) Prefer the neighbor with the lowest bridge ID
4) Prefer the lowest sender port ID
its very confusing, someone please clarify this ASAP, Thanks.
the link 4 d root path selection list i saw is :
http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a00807b0670.shtml
Can anyone tell me What are the latest sim lab for Switch exam?
I have done 3 .
LACP with STP sim
MLS and Eigrp sim
AAA dot1x lab sim
Is there any mor lab should i need to do?
Thank you..
I really liked the article, and the very cool blog
Has anyone had this lab recently in the SWITCH exam? Its not mentioned on the other sites I’ve been looking at.
Hello I need your help and your advice I entered the exam and got the 781 class of 1000 do not know where the problem
But what happened with me is a matter of copy running-config startup-config
Not pleased to work save
In questions lacp, aaadot1x
Possible, help me please reply quickly because I would like to enter the exam next Saturday
Thank you
hi guys my exam is on monday 12th sep, i have done all four labs, LAcp with stp, mls eigrp, aaa, and vtp. any tips for me ???
24 hours to go
15 hrs tik tik tik tik
don dona don done !!!!!!! I cleared the exam on 12th sept . labs were same, copy run start does not work and ip default gateway command does not work. few mcq questions were new but very easy.
Could you post the dump version and which are the labs for exam?
Jimmy, I will plan to write the exam on next week, any tips for me?
i will take my paper tomorrow at 10am.
4 hrs left
Is any one recommended to buy workbook from http://www.passearly.com for CCIE?
To configure the STP bridge priority of a VLAN when the extended system ID is disabled perform this. To configure the STP bridge priority of a VLAN when the extended system ID is enabled perform this.
Bydefault,port gig 1/0/5 is the root port for vlan 40,why we decreas the port cost?
jimmy,could u please share the link of latest dump from where u prepared for the exam.?
Did any one face a situation where after increasing the priority of vlan 20 to 61440 on DSW1 , still CORE did not become the root ? It shouldn’t happen and can’t help if that happens due to no access to them , but curious to know if any other switches had a lower priority for vlan 20 in the topology?
I did not have that problem Madhav. Check your root MAC with show spanning-tree. Also, keep in mind, you will have to wait a second for CORE to take over as root.
Can anyone of please send me the latest CCNP switch dumps and packet tracer labs
salmansaeed101@gmail.com
comeon guys!!I think am asking this 6th timeafter everybody else..DID SOMEONE GOT THIS LAB RECENTLY IN THE EXAM…we have ppl here talking about about exam 642-812 ehehehhe….well this is 813 unfortunately…any body got this one???
hii every one .. i fail my exam yesterday i got 766 .. 2 new lab
its the same topolgy but with TOTALLY difference requirements ..;(
@Bad News – What do you mean 2 new labs ? Kindly explain it more. There are many people waiting to write the exam and it will definitely bring tension to them while they appear for the exams. If you can’t explain it , please refrain from posting such comments as it creates fear to other candidates. Hence kindly show some lights on it and wishes good luck for the new take.
took it yesterday with 967
no new labs present,
dot1x+aaa
eigrp+mls
spanning-tree + channel
hsrp hotspot
probably all of the questions were from pass4sure 6.8
thanks guys.
which is spanning-tree + channel?did u mean LACP with STP Sim?
Great job guys! please kindly help me with the latest dumps for CCNP (switch & T-Shoot). Thank you.
Great job guys! please kindly help me with the latest dumps for CCNP (switch & T-Shoot). Thank you.
please the CCNP (Siwtch & T-Shoot) can be forwarded to my e-mail address simplycooldenny@yahoo.com
Thank you greatly.
please I want a valid exam …. any one have >>? thank u
Can anyone of please send me the latest CCNP switch dumps and packet tracer labs
ethernet16@gmail.com
Thank you
Can someone please send me the last 642-813 switch dumps. I have the lab info just need the dumps.
journeyrocks13@yahoo.com