vlan problem

Unanswered Question
Oct 30th, 2007

http://arifmscelectronics.blogspot.com/

This is the question in the testking as answer is not given. I have the boson software but some command is not running in it. so i have to confirm it.

Q.1 Which port of sw3 is attached to router?

Ans : find out by show cdp neighbor commond

Q.2 Which port of the switch is the trunk port ?

Ans: by show running-config

Now question 3 is created problem for me

Q.3 Out of which port on Sw-Ac3 would a frame containing an IP packet with a

destination address that is not on a local LAN be forwarded?

How can i get the answer of this question and what command should be run to determine.

Q.4 Out of which ports on Sw-Ac3 will a frame be forwarded that has Source MAC

address 0010.5a0a-860a and destination MAC address 000a.8a47.e612? Select three.

and from which command i get the answer of the question 4?

please help.

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ankbhasi Tue, 10/30/2007 - 22:39

Hi Arif,

For question 3)

It will always be fwded on the port which is connected to router VLAN-R1 (I believe this router is doing routing for all vlans). Because when destination address is of some remote subnet then packet need to go to the default gateway which will always be your first hop router.

For question 4)

From the figure you have posted on URL I cannot get these mac addresses belong to which device but you can check for "sh mac-address-table address 000a.8a47.e612". This command will give you the port on which this mac address is learned and then any traffic from any source will always hit this interface.

HTH

Ankur

*Pls rate all helpfull post

Arif,

I have simulated similar problem here:

http://blog.erealmedia.com/wp-content/uploads/2007/10/vlan_med.JPG

I will try to post result from my simulation and answer your problem.

Q1. Use show cdp neighbor [detail]

Sw-AC1#show cdp neighbor

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone

Device ID Local Intrfce Holdtme Capability Platform Port ID

R1 Fas 0/1 178 R PT1000 Fas 0/0

Sw-AC2 Fas 0/4 178 S 2950 Fas 0/1

R1 Fas 0/1 179 R PT1000 Fas 0/0.1

R1 Fas 0/1 179 R PT1000 Fas 0/0.22

R1 Fas 0/1 179 R PT1000 Fas 0/0.33

You can see from the output that there are for R1 (that means Router) connected to port fa0/0, fa0/0.1, fa0/0.22, fa0/0.33. Note that fa0/0 fastethernet port on the router where as fa0/0.1, fa0/0.22 and fa0/0.33 are sub interface on same router (Router on a stick)

Local Interface in all cases is you can see is fa0/1, therefore Router is conneted to Fa0/1 port of Switch.

Answer 2: Show interfaces trunk

Sw-AC1#show interfaces trunk

Port Mode Encapsulation Status Native vlan

Fa0/1 on 802.1q trunking 1

Fa0/4 on 802.1q trunking 1

Fa0/5 on 802.1q trunking 1

Port Vlans allowed on trunk

Fa0/1 1-1005

Fa0/4 1-1005

Fa0/5 1-1005

Port Vlans allowed and active in management domain

Fa0/1 1,22,33,1002,1003,1004,1005

Fa0/4 1,22,33,1002,1003,1004,1005

Fa0/5 1,22,33,1002,1003,1004,1005

Port Vlans in spanning tree forwarding state and not pruned

Fa0/1 1,22,33,1002,1003,1004,1005

Fa0/4 1,22,33,1002,1003,1004,1005

Fa0/5 1,22,33,1002,1003,1004,1005

and also as you said-- Show running-config

also with show spanning-tree

Answer 3: What I understand from this question is that frame IP doesnot belong to local LAN, it means not belong to that particular VLAN, it means it has to be sent to router (via trunk port to router) which will forward to another vlan (it means another IP subnet, as mentioned on the exihibit)

In general answer is the gate of that particular VLAN. To get VLAN gateway. see...

show cdp neighbor detail

Device ID: R1

Entry address(es):

IP address : 192.168.1.1

Platform: cisco PT1000, Capabilities: Router

Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/0.1

Holdtime: 169

Version :

Cisco Internetwork Operating System Software

IOS (tm) PT1000 Software (PT1000-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2005 by cisco Systems, Inc.

Compiled Wed 27-Apr-04 19:01 by miwang

advertisement version: 2

Duplex: full

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

Device ID: R1

Entry address(es):

IP address : 192.168.22.1

Platform: cisco PT1000, Capabilities: Router

Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/0.22

Holdtime: 169

Version :

Cisco Internetwork Operating System Software

IOS (tm) PT1000 Software (PT1000-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2005 by cisco Systems, Inc.

Compiled Wed 27-Apr-04 19:01 by miwang

advertisement version: 2

Duplex: full

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

Device ID: R1

Entry address(es):

IP address : 192.168.33.1

Platform: cisco PT1000, Capabilities: Router

Interface: FastEthernet0/1, Port ID (outgoing port): FastEthernet0/0.33

Holdtime: 169

Version :

Cisco Internetwork Operating System Software

IOS (tm) PT1000 Software (PT1000-I-M), Version 12.2(28), RELEASE SOFTWARE (fc5)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2005 by cisco Systems, Inc.

Compiled Wed 27-Apr-04 19:01 by miwang

advertisement version: 2

Duplex: full

Answer to Q4: show mac-address-table

Sw-AC1#show mac-address-table

Mac Address Table

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

Vlan Mac Address Type Ports

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

1 00e0.b061.5401 DYNAMIC Fa0/4

1 00e0.f9e5.64de DYNAMIC Fa0/1

22 00e0.b061.5401 DYNAMIC Fa0/4

22 00e0.f9e5.64de DYNAMIC Fa0/1

33 00e0.b061.5401 DYNAMIC Fa0/4

33 00e0.f9e5.64de DYNAMIC Fa0/1

Sw-AC1#

arifmscelectronics Wed, 10/31/2007 - 02:36

mean in question 4 i have to check the mac address of all ports in all switch and then decided which is the source and destination port. am i right.

And thank for this.

ankbhasi Wed, 10/31/2007 - 03:18

Hi Arif,

No you do not need to check the mac address of all ports. The destination mac address you mentioned in your original port must belong to some host or network device.

Now switch learns those mac address when some host/network device is connected to switch port and traffic fwding on switc is based on destination mac address so no matter whatever is the source address it will be fwded to the port on which that destination mac address exist.

You just have to issue "sh mac-address-address " command find that mac address exist on which port.

Source mac address given in question 4 is to confuse you and does not have any meaning when it comes to decision taking of fwding frame.

HTH

Ankur

*Pls rate all helpfull post

arifmscelectronics Wed, 10/31/2007 - 10:42

Thanks dear once again for ur support.

As i am going to give the ccna exam on sunday.

can u post me the other output of ur lab to me.

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