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can u help, my book says answer is a I think it's b


?An Ethernet frame arrives at switch SW1, entering on port F0/1. F0/1 does not trunk. SW1 forwards the frame out F0/2. Which of the following statements is true about the logic SW1 uses when forwarding the frame?
a. Forward based on MAC table entries for the F0/1?s access VLAN
b. Forward based on MAC table entries for the F0/2?s access VLAN
c. Forward based on MAC table entries for the F0/1?s native VLAN
d. Forward based on MAC table entries in all VLANs?

Excerpt From: Odom, Wendell. ?CCNA ICND2 200-101 Official Cert Guide.? Cisco Press, 2013. iBooks.
This material may be protected by copyright.

Check out this book on the iBooks Store: https://itunes.apple.com/WebObjects/MZStore.woa/wa/viewBook?id=631319742
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  • LAN Switching and Routing
1 ACCEPTED SOLUTION

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VIP Purple

can u help, my book says answer is a I think it's b

Hi Sinead,

Normally switch forwards process consider entries in mAC table for one VLAN only, means the inbond interface

and for an access interface, that VLAN is the access VLAN assigned to the inbound interface(This is not a trunk port). The VLAN is never determined by the outbound interface (F0/2 here). The native VLAN could not matter because the inbound interface is not a trunk.

So my answer should be :

A: Forward based on MAC table entries for the F0/1’s access VLAN

Hope it helps.

Regards

5 REPLIES

can u help, my book says answer is a I think it's b

Hi Sinead.

Switch does learning, flooding, filtering, forwarding and aging.

When talking about forwarding, the switch perform a look up based on mac address. the mac address table contains mac-address and port association where the mac addrerss was learnt.

If the switches finds the destination mac address in the mac address table, it will check what is the switchport associated with it and forwarded though.

I guess the answer is b... xD ...

Regards.

Wilson B.

New Member

Re: can u help, my book says answer is a I think it's b

Thanks guys for replays, I think the two other answers are like I thought but based on Sandeep.... Answer , I see answer a is correct as based on the vlan and not on basic switch forwarding if no Vlans had been configured

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New Member

Re: can u help, my book says answer is a I think it's b

Sorry but I'm back again! Still unsure ! A or B, I am again going on b as the frame must have a common vlan with fa02 and so the frame is forwarded out fa 02 ..

A switch get frame on int fa01, if it doesn't know where to send it it floods the frame, but by checking MAC address table it find sentry for same vlan as is in frame destination ... That entry has a int fa02 so frame is forwarded out that interface

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VIP Purple

can u help, my book says answer is a I think it's b

Hi Sinead,

Normally switch forwards process consider entries in mAC table for one VLAN only, means the inbond interface

and for an access interface, that VLAN is the access VLAN assigned to the inbound interface(This is not a trunk port). The VLAN is never determined by the outbound interface (F0/2 here). The native VLAN could not matter because the inbound interface is not a trunk.

So my answer should be :

A: Forward based on MAC table entries for the F0/1’s access VLAN

Hope it helps.

Regards

can u help, my book says answer is a I think it's b

Gotta be b. as a makes no sense, because there is no point looking up the ingress port as it just arrived on that port, d is rubbish as it would allow L2 inter vlan switching, which goes against everything VLANs stand for, answer c is just put in there to make 4 options, as Fa0/1 is not a trunk.

example of a mac table entry:

911    0024.142d.57fd    DYNAMIC     Gi2/0/20

which has VLAN and known port


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