Re: SVI Doubt

SVI is a Switch Virtual Interface, however the MAC is very much not
Virtual, The use of a single MAC for all SVI on the same platform is for
save of MAC address's and is relaying on the Rule that in a single
Broadcast Domain there should not be 2 or more same MAC address.

Because each SVI is under a single / separated broadcast domain there is no
problem of re-using the same MAC Address in all the SVI's of the same
platform.

Now for the L3 vs L2, packet is always routed , frame is always switched (7
Layer OSI model).

When user inside VLAN-x want to communicate
with different user/server/node/etc
* it will check first if he have a route to the IP, according to the
IP/Subnet he is at and on his own routing table
* if the IP is in his own subnet and he dose not have an ARPA record he
will generate an ARP hoping to get a responce back and communicate directly
with node
*else if the IP is outside his Broadcast Domain, he will generate an ARP to
the next hop (Router / Default Gateway)
* if he dose not have already the ARPA record for that.
* once he have it, he will send a frame with Destination MAC of the "SVI"
in our case And IP of the Destination node.
* then the switch will get that frame and route the packet according to his
routing table.

On Sun, Dec 25, 2011 at 4:11 PM, CCIE KID <eliteccie_at_gmail.com> wrote:

> Hi fellas,
>
> How does a L3 switch recognize that it should switch the packet or do the
> routing engine. To my understanding If a frame is received with the SVI MAC
> Address ( Virtual MC ) if there is a L3 Switch and it is running SVI
> interface as its gateway..
> And that is the gateway given to the host machine.
>
> So when it receives a frame with SVI MAC, the packet will be send to the
> routing engine.
>
> Correct me if i am wrong
>
> How does the L3 switch internally knows that frame is to switch or send it
> to the routing engine? How does it decide ?
>
>
>
>
>
>
> On Sun, Dec 25, 2011 at 6:44 PM, shiran guez <shiranp3_at_gmail.com> wrote:
>
>> When performing a show version you can see:
>>
>> *Base ethernet MAC Address: *XX:XX:XX:XX:XX:XX
>>
>> That is the address used by the SVI (all of them)
>> And all the other ports are incremented
>>
>> So
>> F0/1 will be XX:XX:XX:XX:XX:X1
>> F0/2 will be XX:XX:XX:XX:XX:X2
>> ...
>>
>> On the MAC address table you can see the STATIC and normally the first
>> MAC is the SVI's MAC, the others are the physical ports
>>
>> sh mac address-table | in STATIC
>>
>> For a SVI to transition to the port stat up/up
>>
>> You must have the following conditions:
>>
>> * vlan must exist in VLAN database
>> * vlan need to be assigned to at least one switched port
>> * and the port must be in STP forwarding state
>>
>> if all this are met the port will transition automatically, and that is
>> what called SVI autostate
>>
>> Regards,
>>
>> Shiran Guez
>>
>> On Sun, Dec 25, 2011 at 2:47 PM, CCIE KID <eliteccie_at_gmail.com> wrote:
>>
>>> Hi fellas,
>>>
>>> I am having a SVI interface. when a host arp for the default gateway MAC,
>>> the Layer three switch forwards the SVI Virtual MAC to the host . Where
>>> does the SVI Virtual MAC ?. Is the virtual MAC gets stored in normal MAC
>>> table ?
>>>
>>> Wat does SVI Autostate mean exactly. Can anyone explain me Autostate ?
>>>
>>> --
>>> With Warmest Regards,
>>>
>>> CCIE KID
>>> CCIE#29992 (Security)
>>>
>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
>>> Subscription information may be found at:
>>> http://www.groupstudy.com/list/CCIELab.html
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>> --
>> Shiran Guez
>> MCSE CCNP NCE1 JNCIA-ENT JNCIS-ENT CCIE #20572
>> http://cciep3.blogspot.com
>> http://www.linkedin.com/in/cciep3
>> http://twitter.com/cciep3
>>
>>
>
>
> --
> With Warmest Regards,
>
> CCIE KID
> CCIE#29992 (Security)
>
>
>

-- 
Shiran Guez
MCSE CCNP NCE1 JNCIA-ENT JNCIS-ENT CCIE #20572
http://cciep3.blogspot.com
http://www.linkedin.com/in/cciep3
http://twitter.com/cciep3
Blogs and organic groups at http://www.ccie.net