regarding vlan and root

Unanswered Question
Jul 21st, 2007

Hi all

I am a frustrated CCNA candidate. I have failed the exam (640-801) for a couple of times.Last time i got 847. I need to know several things.

In the exam there was a simulated lab with multiple switches and routers connected together and I was permitted to access the switch through console. There was several vlan configured. And in the question asked what is the root for vlan 1. Now I am telling you what I did,

I entered sh spanning-tree vlan 1 to find the root. But I found that switch is not root. Then I applied sh mac-address-table to find out which port is to the root (that matched with root bridge?s MAC address). Then I applied Sh cdp neighbors detail to find ip address and the port. Then I tried to telnet to that address but It was said password in not set. So I could not able to telnet to that neighbor switch to find the root. Now Can you please explain what was my mistake and how can I find the root?

In the same network in another question ip was given and asking for its MAC address.

I tried to see sh arp to find MAC but the ip was not there then I tried to ping that ip address It failed then I tried to trace the address it failed 30 times. Can you please explain what was my mistake to find that MAC.

As I know in a multiple vlan environment the vlan?s are in different subnet. Does it effect on communication between the vlan?s if I put switch ip address on different mask/subnet according to routers Fast Ethernet interface (not sub interface). Because I know switch ip is only for management purpose.

One final question

Is it possible to get feed back from cisco for the questions that I answered wrong for a particular exam?

You will be highly appreciated for your kind help. Please please help me to come out from this frustration.

Many many Thanks in advance for your kind help.



(I only have simulated software Boson netsim to practice the configuration.)

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ross_rulz Sat, 07/21/2007 - 02:54

Hi Milon,

When you type show spanning-tree vlan 1 it will display the root id and bridge id. The root id is the root bridge which will display the MAC address and switch priority of the switch. The bridge id is the MAC address of the local switch which will also display its switch priority.

In regards getting feedback from Cisco they will not tell you what questions you got wrong or right. You just have to keep studying hard and try and get some experience with real routers and switches. Try and stay away from these simulations because you are restricted to what commands you can do. With real routers and switches you can setup your own labs and do real troubleshooting.

Hope this helps.


milon12345 Sun, 07/22/2007 - 11:30


thanks for your prompt reply. I know what is root mac and what is bridge mac. I told what i tried in the exam to find the root and mac add of another ip address. Can you please clear me on that point?


mark.j.hodge Sun, 07/22/2007 - 11:50

If you want to translate MAC addresses to MAC addreses on a switch take a look at the arp cashe with the "sh arp" command.

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