no switchport help 3550

HELP __Please set me start on this

If you have a 3550 three layer EMI switch and want 3 vlans to be different (not talk because they will be from different domains) I know how to make vlans and assign ports to them and give the vlans ip addresses, and make access-lists a well? Now this is where I get alittle lost,.I think i have to make a port, a no switchport to talk to router and vlans, on the no switchport I give it ip addresses,such as 0/12 no ip, then subinterfaces 0/12.1 x.x.x. x..x.x. x.x..x and then also give ip addresses to subinterfaces 0/12.2 , 0/12.3 with the same subnet that is on the routers subinterfaces for they can talk, now do I IP route each vlan ip addesses to the correct subinterface on the no switchport subinterface, which would mean I would config 3 IP route commands to correct subinterfaces. am i even close?? Thanks mike

Hi mic

I understand here that you have a separate router connected to the 3550 and that you want this router to do the routing for the 3 vlans. In other words you don't want the 3550 to use it's layer 3 features and route for the 3 vlans.

If the above is correct, then the typical way to do this (after configuring the vlans on the 3550 and configuring the sub-interfaces on the router with the correct IPs/masks. And configuring VLAN IDs for each sub-interface using the encapsulation dot1q command). After doing all this you have to convert the port on the 3550 that is connected to the router to a TRUNK port. Some thing like this:

[code:1]Switch(config)# interface FastEthernet0/2
Switch(config-if)# switchport trunk encapsulation dot1q
Switch(config-if)# switchport mode trunk
Switch(config-if)# no ip address[/code:1]

Replace FastEthernet0/2 with the port you have. No need to add static routes on either side in this scenario.

However, if you have some thing else in mind, then please clarify and we'll try to figure.

thanks