Native VLAN - usage on multiply physical interfaces?


I have a situation which is somewhat stumping me, and I'm looking for the voice of wisdom from someone who maybe understands the concept of the "native" VLAN for trunking better than I do.

I have a single router - a 3745 - which connects to a number of switches, and from there on to other devices. It has two gigabit iterfaces & 4 fast ethernet interfaces, and is running the Enterprise base feature set IOS.

Connected to each gigabit interface, I have a 3500 series switch which each carry a different set of vlans via trunk links.

I've configured a "native" vlan on a sub-interface for each gigabit interface, as well as other sub interfaces for the relavent vlans.

What I want to do is use one subnet range for the cascaded switches management vlan, or vlan1. I have configured the native interface on the first interface with an IP address and subnet range, and all the cascaded switches work fine.

However, when I configure the second gigabit interface with a native interface with the same vlan ID as the first, I can't get any IP connectivity from the native vlan on the cascaded switches on the range.

show vlans gives me this

Core>sh vlans

Virtual LAN ID: 1 (IEEE 802.1Q Encapsulation)

vLAN Trunk Interfaces: GigabitEthernet2/0.1 GigabitEthernet3/0.1 FastEthernet4/1.1

This is configured as native Vlan for the following interface(s) : GigabitEthernet2/0 GigabitEthernet3/0 FastEthernet4/1

Protocols Configured: Address: Received: Transmitted: IP 9096282 989405265

My understanding of how this works is that being the "native" VLAN is the same ID on each downlink switch, all I should have to do is assign an IP address in the appropriate range, set a default gateway and all should work. However, this doesn't work - and I don't know why.

Can anyone shed some light? Is what I want to do even possible?



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