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3660 + 16ESW + 1GE VLAN problem

I have a 3662 + 16ESW + 1GE. The Gi5/0 native vlan is vlan 1 & has an ip address. There are also subinterfaces (Gi5/0.31, .32, etc), each with addresses. I route between these and all is well. None of the other LAN interfaces are used (though there are WAN interfaces and these work fine).

Added the ESW module (6) wanting each of the interfaces to be access ports in vlan 1.

Interface Fa6/x

switchport access vlan 1

switchport mode access

no ip address

etc.

I can't see anything connected to the ESW.

If I put the address from Gi5/0 on int vlan1 (& no ip addr on Gi5/0), from the router itself or over a WAN interface, I can see the ESW devices, but nothing thru the Gi5/0 interface.

How can I see BOTH Gi5/0 native vlan 1 AND ESW 6/x access vlan 1? I don't want to introduce a cross connect from a port on the ESW to another device in the LAN as I want the devices connected to the ESW ONLY dependent on the 3660 and not some other device.

I'm running 12.3.2 Enterprise.

1 REPLY

Re: 3660 + 16ESW + 1GE VLAN problem

Hi,

my understanding is (this is the way it works on Cat3550, I've got no experience with 3660 ESW):

If you add ip address to a physical interface (no switchport command necessary)or a subinterface it becomes a routed one.

If you add ip address to a VLANx interface (no shut necessary) you can route to/from all the switching ports in VLANx.

You can

1) configure traditional "router on the stick" with ip-addressed subinterfaces (including one subinterface for native VLAN, assigning IP address to the interface is just a workaround for "encapsulation 802.1q native" option lack in older IOSes). You can add switching ports to any VLANs but they remain not routed (you need external physical connection to route).

2) configure a trunk port (I'm not sure if 3660 is capable) without any subinterfaces. You need to configure int VLANx (and add an IP address to it, no shut) for each VLANx which you want to route from/to.

Switching ports assigned to VLANx will then be able to route from/to this VLANx.

So if your 3660 is capable to configure trunk ports the 2) configuration might be what you need.

Regards,

Milan

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