can you use SVI with onboard ethernet interfaces on the 3945 NPE 150

nday · ‎07-21-2014

can you use SVI with onboard ethernet interfaces on the 3945 NPE 150.

Can you use the interfaces as trunk interfaces and then use a "interface vlan xxx" or are you required to simply use sub interfaces for VLAN support?

Hoping to use SVIs instead of sub interfaces so I can have two uplink trunks serviced by a single SVI.

Martin Hruby · ‎08-03-2015

Hello

Unless you have an Etherswitch card present which provides you with Layer 2 Ethernet ports (e.g. HWIC-4ESW or HWIC-D-9ESW) then you cannot create SVIs. In default Cisco 3945 configuration with only on-board routed (Layer 3) Ethernet interfaces, you have to create logical sub-interfaces.

If I understood you correctly and you want traffic from different trunks to be handled by the same IP on the router, the solution might be Integrated Routing and Bridging (IRB). You basically create a bridge-group (e.g. bridge-group 10) and assign different physical or logical interfaces into it. Then you can create a Bridged Virtual Interface (interface BVI 10), just like you would an SVI and configure it with an IP address which is then reachable from all interfaces also part of the same bridge-group. Don't forget to configure bridging of Ethernet frames as well as routing for the IP protocol in the bridge-group. Have a look at this configuration guide:

http://www.cisco.com/c/en/us/support/docs/lan-switching/integrated-routing-bridging-irb/17054-741-10.html

Best regards,
Martin