SVI and L3

Unanswered Question
Aug 2nd, 2006

Hi All,

I am still a little confused about adding a hwic to my 2821 router for more ethernet ports. I have learned that the switch ports on this module do support L3 but only when assigned to an SVI. My questions come into play when a device is connected to the switch ports. say i have the SVI with an ip of 10.0.0.1 and the connected device with an ip in the same subnet. when i plug into one of the switch ports the device is going to be able to talk just as if I had supplied the ip directly on the interface as the onboard interfaces work correct? otherwise, whats the use?

TIA,

R

I have this problem too.
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Richard Burts Wed, 08/02/2006 - 07:56

R

Essentially the hwic is a VLAN and the SVI is the VLAN interface. You create the SVI and assign an IP address on it to enable IP layer 3 processing. The physical ports are layer 2 ports and need the SVI for layer 3 capability. If you assign 10.0.0.1 to the SVI, and connect a PC to one of the ports, assign the PC an IP address in that subnet, and configure the PC default gateway as 10.0.0.1 then the PC should have IP connectivity just fine.

HTH

Rick

rhltechie@gmail.com Wed, 08/02/2006 - 08:34

Thanks for your reply. Do you think it matters if I am using this as an external public address? i need another fast ether int to put a microsoft isa server side by side with my pix.

TIA,

R

Richard Burts Wed, 08/02/2006 - 09:26

R

I am not sure that I fully understand your follow up question. In one perspective it does not matter to the router whether the address is external public, internal private, or whatever. The router has an address that it will use to provide layer 3 functionality for this VLAN. In other perspectives of what connects to what, or how routing is going to work there is certainly a significant difference between assigning an external public address or an internal private one. The type of address that you assign should be consistent with the topology of the underlying network.

HTH

Rick

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Posted August 2, 2006 at 7:17 AM
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