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New Member

SVI Interface on ACE


SVI Interfaces are supposedly for communication between the MSFC and the ACE. So the command

interface vlan 250 configured on the 6500 Switch would enable SVI on the MSFC.

In our setup we have multiple contexts on the ACE and our VPN box sits behind an inside switch.

The VLAN defined for the outside VPN interface is say 200... so why would we define a SVI interface.. interface vlan 200 on the 6500 switch which is actually our border that connects to the Internet.

Is it because it should be routable from the Internet?

If so what is the difference between an SVI Interface (Connection between a switch and ACE) and VLAN L3 interface


Cisco Employee

Re: SVI Interface on ACE

you don't need the SVI interface on the MSFC if you have an external device doing the routing for the ACE.

You need to configure the SVCLC on the MSFC to tell which vlans are allowed on the trunk to the ACE.

Traffic coming out of ACE is inside a trunk and will be L2 switched to either an external gateway or to the 'interface vlan x' of the all depends on the destination mac-address.


New Member

Re: SVI Interface on ACE

I get the point, but if I dont define interface vlan 200 on the 6500 switch then how will the switch route the traffic to the VPN box.

The 6500 is the border router that routes traffic.

So my question is even if the VPN device is located external to the switch/ACE will that VLAN 200 still be communicated to the ACE contexts? that VLAN does not reside in any of the contexts because its not meant to be for the ACE.

So in the VPN VLAN case, i use it only to route traffic to the VPN box?

I am asking this only to clear a doubt of my mind. Appreciate your response


Cisco Employee

Re: SVI Interface on ACE

The Cat6k will not "route" the traffic from the ace to the vpn ... it with "switch" it....

the difference is that as long as the traffic is part of the same vlan (ie: 200) the switching is done based on the mac-address.

So if ACE sends the traffic with dest-mac == VPN-device, the Cat6k will see traffic coming from ace vlan 200 and with destination vpn-mac-vlan200 it will just switch it to the corresponding interface.

When you create an 'interface vlan X' on the cat6k you actually create a L3 interface... in the old days there was a Sup and an MSFC.

The Sup did the switching and the MSFC the routing.

The 'interface vlan x' command was to conigure the MSFC.

But it is not required for the Sup to switch traffic inside a single vlan.

Same idea here.